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Tesla Motors Announces a New Home Battery (offgridquest.com)
289 points by jnaveen on Feb 17, 2015 | hide | past | web | favorite | 217 comments

So, where does lithium come from? It comes from the Earth, of course, but it doesn't require strip mining or blowing the tops off mountains like other resources do...most often, lithium is found in briny underground ponds. The liquid is pumped out and left to dry in the sun.



Mining is mining. There isn't a "green" form. Tearing holes in the earth is not the worst ecological damage or the great health risk. The big problem is the water...and it will run downhill from the Andes and wherever else Lithium is mined and into the Ocean.

The house off the grid is built on industrial infrastructure.

    The house off the grid is built on
    industrial infrastructure.
So what? It's a matter of degree.

I helped my parents build their off-the-grid house. It's solar-powered, but uses batteries for backup storage. It collects and filters rainwater, recycles and purifies its own sewage, and is made mostly of recycled materials (in the style of what's called an "Earthship," but with a more traditional, house-like form factor).

Did industrial infrastructure come into play? Of course. We used cars and trucks to get stuff there to build with. We used machines and materials produced in the modern world. What difference could that possibly make? The house is still much less ecologically destructive than the vast majority of dwellings worldwide, both in terms of ongoing damage and initial construction.

It's possible to create buildings today which get all their electricity from the sun; which require no industrial infrastructure at all for sewage, heat, or clean water; and which cost much, much less than earlier housing models. That's an amazing improvement.

All tech's based to some degree on tech which came before.

> The house is still much less ecologically destructive than the vast majority of dwellings worldwide, both in terms of ongoing damage and initial construction.

The isn't even close to being true. The majority of dwellings worldwide lack what you would call basic utilities and are constructed using local materials, many of which are recycled.

Perhaps you meant the West?

Even then, it's not true. Solar panels, batteries, modern insulation, etc ... these create a ton of pollution during manufacture. Not to mention drilling wells and installing septic tanks as opposed to hooking up to public utilities.

Also many municipalities don't allow battery 'grid-tie' with the option of 'off the grid' living. For example, Connecticut has laws which don't allow houses to have batteries that would allow a house to be self sustaining and have a connection to the grid. This is because if you have batteries which cause a back flow during a power outage to the power station, an electrical worker could get shocked down the road.

The fact that lithium batteries aren't the greenest combined with the fact that you can't even live 'off the grid' in a grid tied system is a big uphill for these batteries.

The same issue exists with grid connected solar panels. My solar panels are designed to stop working whenever there is a power outage. This is a legally mandated requirement here and is very annoying when it happens on a beautiful sunny day.

A solar panel installer told me that if I add a battery backup to my installation, then at least it'll still charge the batteries during a power outage.

This is the dumbest mandate I have ever heard of. Part of the installation of such power systems should have a mandate that in order for an off-grid power system to be connected to your box, your breaker to the grid must be off before you can enable your off-grid system. Why isn't there a mandate for this?

It seems like the mandate was written entirely to protect the power company's profits hiding behind a thin veil of trying to protect their technicians.

If the electrical utilities cared at all about the customer they'd mandate something that allows customers to do what they want, safely.

What good is charging batteries during the power outage when you can't use them during a power outage? You can't have power connected during the power outage for fear of "electrocuting the technicians" - so what's the point in spending all this money on solar panels if the only time you can use them is while the grid is up... and you have cheap (comparatively) grid fed electricity? What's the purpose in having batteries if not to use them when the grid is down?

In the US, rural electrification was largely complete 75 years ago. Urban electrification infrastructure dates back even longer. In all that time, intensity of use has increased.

There's a lot of bailing wire and duct tape...or overhead power lines and wood poles if you prefer...in the grid. It's grown based on small decisions over many years. People won't put up with six years of service interruptions while big chunks are rebuilt and debugged...nor will they be happy to underwrite the cost of doing so.

It's BS as you rightfully detected but that doesn't stop the State cheerleaders above from giving us 1001 reasons why this is bad and we must protect the lives of electrical workers, firefighters, and even the lofty goal of protecting the hand-wavy "public commons" itself!

Yeah, it's not the power company's fault for endangering the lives of their workers, it's our fault, you and I regular Joes, for daring to want electricity in case the power company can't supply us with any. How dare you?

This doesn't make any sense. There are almost certainly provisions in the law for backup generators to be connected to the service panel with a transfer switch, either manual or automatic. The idea is that when the generator is powering the house, the powerline service is completely disconnected, and vice versa. This is standard stuff, part of every electrical code I've ever heard of.

If a state legislature doesn't allow backup power to be supplied to a home or business with an NEC-compliant transfer switch, there should be some kind of judicial recourse. I'd spend some quality time with an attorney before taking "No" for an answer.


Either your sarcasm tags are missing or you're just simply dead wrong.

I set up a fairly beefy solar/wind powered system in an off-grid configurations specifically not to have to deal with the red tape, installation and insurance requirements of being 'on grid' and I don't regret that but all of those requirements, inspections and gear made perfect sense from an electrical point of view and from a safety point of view.

There are some ways around that limitation. The reason it exists in the first place is so that the power company can safely power down their lines without installations such as yours feeding power back into the lines that are supposedly safe. This on the off chance that you'll end up electrocuting a line-man, which makes good sense.

Of course, since your puny little solar installation is incapable of powering a substantial portion of the grid this usually only really becomes a problem when the section that is islanded is small enough.

Some electrical codes allow you to resume powering your own circuit if you physically lock-out your connection during such an outage, and re-configure your inverter to non-grid connected mode.

You will also require a battery in such a case since the stabilizing properties of the grid (it's a very large load and acts as a huge flywheel or capacitor with basically endless capacity from the point of view of your installation).

And of course when the grid outage has been dealt with and you wish to feed power back into the grid again (or consume when the sun is down) you're going to have to undo all of this.

When I built a solar / wind power installation in Canada I decided that the net metering laws and price of power produced by renewables was so low that I scrapped the whole grid connectivity portion and invested the surplus into a much larger battery.

It felt pretty good to have power when the island was down which happened many times every year.

"you're going to have to undo all of this"

Why can't "all of this" be packaged into one idiot-proof box with connections to the grid, your off-grid system, and your house?

You mean like a generator transfer switch?


That's a device that you probably don't want to use with your solar installation since it will not handle the grid-present resynchronization at the end of a power outage correctly which could cause your renewable energy system to be re-connected to the grid at 180 degrees out of phase worst case when grid power is restored. The result will be a big bill for a large number of power FETs or IGBTs depending on the tech used in your inverter.

So you can't just add an automatic transfer switch to retro-fit this to an existing inverter, but there are plenty of inverters where an option for an external module can be purchased or where an automatic transfer switch is built into the inverter itself:


These inverters will first synchronize with the grid before they connect.

Depending on local variations in electrical code it can be. But check with a licensed installer familiar with your local code.

Yes it's not such a problem when it's just my 5 KW system. However here in Perth, Western Australia there are a lot of sunny days, so domestic rooftop solar systems are very commonplace now.

In my case there's some significant financial incentives to stay connected to the grid (I actually get a cheque from my power company for most of the year). That'll change in another 6 years time when this higher buyback rate expires, so I'll be looking very closely at whether I want to remain grid connected at that point.

That's allowed in Connecticut:


$300,000 liability policy requirement right at the end there.

There's also similar rules for installed generators, it's not clear to me how they would treat a big battery.

That may be the reason why the law was made, but that situation simply does not exist in reality. Any 'off-grid enabled' battery system that's worth anything at all would isolate the house from the grid when it kicks on, else all manner of bad things could happen, including having your battery drained on somebody else's load or the aforementioned electrical worker zappage. It's also trivially easy to accomplish said isolation.

Such regulations provide several types of protection to the public commons.

Another group of people who are protected are firefighters. In a typical residential installation the power meter also serves as the service disconnect. Response protocols include pulling the meter before many other life saving and property preserving operations. Live equipment and conductors operating from a second source downstream of the meter are a serious hazard to fire fighting personnel.

Solar panels are a particular hazard because the sun doesn't have a disconnect, many firefighting operations involve working on the roof, and fire burns upward. A collapsed roof may bring a tangle of live electrical parts down into the building and create a hazard that persists long after the fire has been suppressed.

In addition, miscellaneous loads applied to a grid can bring it down. In the Northeast US, much of the infrastructure is old and therefore less robustly engineered than elsewhere.

Am I missing something?

When you trip the breaker, the power is still on as far as the box in your house - unless it's shut off by the power company, it's just off inside the house. When you have alternative energy sources that include batteries, the same thing applies. The power from your batteries still runs through your box/breaker (via an inverter), and onward into the house. If you shut the box off, the power is off inside the house, regardless of where the power is coming from.

What's the difference?

In a typical US installation, the connection between the utility service and the dwelling service is made at the meter box. The meter forms the physical connection. When it is pulled, utility service is cut.

Secondary sources of electrical power such as solar panels, batteries, etc are connected downstream of the meter, i.e. connected to the load side from the perspective of the utility provider. Pulling the meter disconnects utility service but does not disconnect the secondary sources of electrical power. The dwelling therefore remains energized [and that's the point of installing such systems].

The difficulty in deenergizing the system presents a hazard. Finding and identifying the various disconnects takes time and is subject to error: who knows what was done for convenience or through poor planning or plain old stupidity.

Even if there is a disconnect for a grid of solar panels this only deenergizes the load side of the grid. Panels exposed to sunlight remain energized. Similarly lead acid batteries maintain an electrical potential when disconnected from the load side.

That you might not be there when you need to go to island mode or that you might not even be aware that the grid is down because you and a bunch of neighbours are capable of sourcing enough power that your 'off grid' detection mechanism fails.

There are solutions for this, it costs a little bit of money and depending on local regulations it may or may not be allowed.

So yes, you can override this and if you mechanically disconnect from the grid then you are typically allowed to operate your installation in island mode. But if you get caught backfeeding the grid when the grid is down then you will more than likely lose your hookup.

Most cheap/light inverters need an external power source to sync to and will automatically shut down if the grid is not available for synchronization purposes, which makes them compliant with the demands of the utilities. If you want to go to island mode you'll need a system that is considerably more expensive (batteries, load based inverter rather than generation capacity based) than one that can't.

There is no "detection" system. You are the detection system. There is no way of enabling your off-grid connection without shutting off the on-grid system. The interlock switch physically prevents you from switching on the trip for your off-grid system while your on-grid system trip switch is on https://www.youtube.com/watch?v=GbtRxcb-cmA

When the grid goes down, your power goes down. You then have to go trip the switch in your box to shut off the power between the grid and your house. Only then can you switch on the trip for off-grid power bringing the power back up in your house.

I guess you could have some kind of a relay where on-grid power would flow right through, but if on-grid power goes off, the relay redirects the circuit to your off-grid power - I think this is the basic principle behind the automatic transfer switch. Being on vacation or "not detecting a power failure" isn't really an option because as long as there's power, the power would flow into your electrical box from the grid. As soon as the power goes out, the relay that connects the circuit from the grid to your power box would flip to your off-grid circuit. The two circuits aren't connected but your household power can run from either one or the other.

I guess if you're wanting to sell power back to the grid, or supplement your power needs, that's different, but if it's a grid vs. off-grid situation, there isn't a problem.

And last but not least: when disconnected solar panels are 'open circuit' and the voltages will rise very rapidly. You can arc-weld with two fully illuminated 48V panels in parallel.

It's also not a theoretical concern for disconnected panels either; my late father was consultant in a lawsuit where a small mechanical design flaw in the solar panel connector boxes combined with rough installation procedures caused farms all across France to go up in flames.

It's also not that strange considering the farms would often have 20+ panels generating multiple kVs worth of electricity. Afterwards he refused to put any panels on our home without having a proper micro-inverter installed.

that is an interesting fact! wonder if there is a simple solution like a chemical blinder, that could be integrated into something sort of like a "EPO" button, making the panel inert in terms of voltage when hit? Just like the fire rescue folks can pull a breaker or service disconnect for traditional mains?

A properly wired transfer switch fully cures that risk.

A couple of my architect friends -- and they are good competent architects who spend the proper portion of their fees to hire competent consulting engineers -- designed an emergency services center a few years ago. The hurricane came - the project was in Florida - the utility cut grid power per protocol and the automatic transfer switch didn't flip to onsite power. Neither did the backup automatic switch.

The person trained to operate the manual switch was on a scheduled vacation (hurricane season in the US is six months it ain't reasonable to prohibit vacations). It took over an hour to get the system back online. Now keep in mind that all of this was with emergency services grade equipment trained professional staff and regular inspections and testing. And everybody wasn't away on vacation by policy.

Proper wiring is a necessary, but not sufficient condition. Power grid failures are many sigma events.

> The person

And there's the problem.

The HIL was the backup to the backup.

[HIL]: https://en.wikipedia.org/wiki/Human-in-the-loop

And even though the solution is right there, power line worker remains the ninth deadliest job in America.


On trip through Minnesota, I watched a helicopter ferry guys up onto the towers to work (they dangled from the helicopter and then transferred over to the tower: http://www.capx2020.com/ ). They were building the type of infrastructure the news says America doesn't know how to build anymore.

I wonder if energized lines are the big problem.

Workers can safely work on live high voltage lines, if they're wearing a Faraday cage "hot suit" and not grounded: http://youtu.be/LIjC7DjoVe8

That video is awesome. I've seen a version with much better quality that really gets my acrophobia going... ;-)

(It's likely there are many -other- hazards to power line working, beyond presence or absence of transfer switches at on-site generators.)

If you are a lineman, you are three times more likely to die from electrocution than from a fall.

(They die from electrocution at 35x the normal population rate, while the death from falls is 5x the normal population rate.)


That's just fatalities, ignoring the other dangers like getting your arms blown off.

True, but bewary of automated transfer switches. I have seen DC's fail due to ATS's not doing their job. This can be pretty dangerous for a lineman/fire rescue if your particular ATS fails to switch...

For people who are more interested in these topics, you'll want to investigate "anti-islanding", UL-1741, and IEEE-1547.




...if you wanted to power your house from a battery-fed inverter you'd have to install an automatic transfer switch, just like if you had a back-up generator.



> because if you have batteries which cause a back flow during a power outage to the power station, an electrical worker could get shocked

What is the difference between Battery backup and a wind turbine/solar? Somehow you are allowed to have solar and pump back to the grid, but not battery, geee wonder why that is.

This is an issue even without battery storage. Solar and wind generation that is set up to feed excess back to the grid already has to have a way for the utilities to shut it off. This is why you have to have your setup vetted by the utility if you are feeding the grid.

Then that electrical worker would have to take precations (like disconnect the system), no? Sounds like it's just something that can be held in account. Plus the battery could not flow back to the grid in case of power outage (but instead power the own house first)

Any reasonable grid company should not only not prohibit this, but welcome it and pay for energy people feed back into it. I can call mine any day and have a bi-directional meter put in so I can charge for it, should I ever choose to install solar panels.

In some states, it is required by law that the power company pay for home generated electricity that is fed back into the grid.

Why is this not an issue if you have solar cells or wind mill or whatever?

I'm not an electrician, but that sort of thing seems trivial to prevent? Surely there are ways to stop the current from passing through the cables where the outage happens, or somewhere near it?

> This is because if you have batteries which cause a back flow during a power outage to the power station, an electrical worker could get shocked down the road.

Surely there is some safe way of preventing this?

There is. The same issue is present with home generators, and most cities require they be installed by a licensed electrician who will ensure it doesn't power the grid in an outage.

I would think so, and I would hope they would implement it. Especially considering the benefits to society of having people who are more prepared and self-sufficient, I would hope that safety would be only one of the reasons they wouldn't rely on people obeying some regulation for their worker's safety.

Living in CT, is my gas generator considered a battery?

>This is because if you have batteries which cause a back flow during a power outage to the power station, an electrical worker could get shocked down the road.

If I were an electrical worked I'd treat a power line like it was live regardless of whether there is a power outage or not.

>you can't even live 'off the grid' in a grid tied system

I can't find any references for your stated claim about Connecticut, however it seems deeply illogical given that a generator (which surely aren't banned), solar panels, wind, etc, all have the potential of feeding energy back to the grid in an outage. Which is why there are regulations and home inspections and all of that, to ensure that the appropriate safeties and switches are in place. Simply banning one of many possible mechanisms of generating power would be very short sighted.

Many regions that offer feed-in time-of-day tariffs are rightly trying to figure out how to accommodate battery systems, where some users are trying to game the system by charging a big battery array during low cost hours, and then "selling" it back to the grid during peak hours (at inflated, subsidized prices).

EDIT: As a reply to msandford, given that I can't reply lower -- the reason they have this limit is that the tariff price paid to home solar/wind generators is way above the bulk, "wholesale" price of power. It was created as an incentive to encourage green energy. So when you feed back their own power to them, it does them no favor given that now they're paying 2x+ what they would pay on the normal power market for power, and simply undermines the entire incentive program.

> where some users are trying to game the system by charging a big battery array during low cost hours, and then "selling" it back to the grid during peak hours (at inflated, subsidized prices).

The idea that a utility wants a heads-I-win-tails-you-lose kind of situation is annoying at best and downright infuriating at worst. If they're willing to sell power for $X now and willing to buy it later for $Y, what does it matter the method? I mean, there are people working on grid-scale storage batteries to do precisely that because utilities desperately NEED additional peak capacity when it's a hot day and everyone's A/C is on in the late afternoon. Why would it be OK for the UTILITY to utilize grid storage, but not an INDIVIDUAL?


  If they're willing to sell power for $X now and willing to buy 
  it later for $Y, what does it matter the method?
In the UK, to encourage adoption of residential solar panels there is a scheme of "feed in tariffs" where you can generate renewable energy and receive a guaranteed, above-market-rate price for it. The goal of this is to reduce carbon emissions.

For example, you can buy residential electricity for 15p/kWh [1] but sell energy from your small hydro installation for 19p/kWh [2].

Obviously, the goal of reducing carbon emissions would not be achieved if people simply charged batteries at 15p/kWh and sold it back at 19p/kWh!

Of course, this issue only arises because feed in tariffs are subsidised.

[1] https://www.gov.uk/government/uploads/system/uploads/attachm... [2] http://www.fitariffs.co.uk/eligible/levels/

Honestly, let them! They'll go bankrupt soon enough. And they'll achieve peak shaving in the process.

Lead acid batteries cost about $100/kWh of nameplate capacity, more like $200/kWh of usable storage. At a 50% depth of discharge you're going to get about 1000 cycles out of the battery.


So assuming 100% charge, discharge, charger and inverter efficiency (reality is more like 60% through that whole cycle) a person stands to make about $0.06 per kWh per cycle (in the UK anyhow) and they can only get 1000 cycles.

$0.06 * 1000 = $60 per kWh per battery lifetime

That's only 1/3 of the cost of the batteries, completely neglecting the capital cost of the charger and inverter and the time spent to set the whole thing up. Further, once you take the realizable efficiencies into account, it's more like $40 not $60 so they're losing money even faster.

This is a problem that -- at least for now -- LITERALLY solves itself.

And they'll achieve peak shaving in the process.

Peak shaving is if you powered your own home off of your battery pack during peak times. The whole issue is that gamers -- who are essentially ruining "the commons" and pissing in the drinking well -- are instead abusing a system.

Again, no home battery pack is helping the power company. The rates are hugely subsidized to encourage green energy. The people who abuse it simply ruin it for everyone else.

You're right of course that it's not peak shaving, which is about shedding load. That was incorrect of me to state.

But it is peak generation, which is just as valuable.

> Again, no home battery pack is helping the power company.

Please re-read my comment where I detail the economics of pulling power off the grid at low price and selling it back at high price is actually net-negative for the individuals doing so. From this we can assume that it's net-positive for the utility company because they're basically getting "free money" from the people who aren't good enough at math to see that what they're doing is economically wasteful.

> The people who abuse it simply ruin it for everyone else.

The people who "abuse" it are paying $0.20/kWh of cost to make $0.06/kWh of revenue. That's REVENUE, not PROFIT. This is a losing strategy, it loses $0.14/kWh, at least according to the math I did.

It's entirely possible that my analysis is wrong for some reason, but rather than just stating "they're ruining it for everyone!" maybe you could rebut my reasoning or something? Just stating something as a fact doesn't make it so.

Peak generation... are you referring to Tea Time?


It isn't just as valuable. Again, the wholesale market rate is significantly less than the subsidized tariff that they pay homeowners to feed back.

To your final paragraph -- you essentially made up numbers and then demand that I refute them. 10. 14. 1.3e12. Refute that.

The single and only reason this side discussion even happened is that I noted that some power companies will refuse to allow grid feed-in if you install battery packs, for the reason I noted.

Did you even re-read what I wrote?

Lead acid batteries cost about $100/kWh nameplate. But at 100% depth of discharge they wear out VERY quickly. We'll assume 50%. That means they cost $200/kWh in actual capacity.

At 50% depth of discharge a lead acid battery will only get about 1000 cycles before it's not very useful anymore and needs to be replaced.

$200 / 1000 cycles = $0.20 per kWh per cycle.

That's the fixed cost of a lead acid battery. Every time you charge and discharge it, you've lost $0.20 per kWh in terms of the capital cost of the battery. This has nothing to do with the price of power, but it has to do with the depreciation of the asset.

Okay so now let's deal with power cost. It's 14p to buy low, 19p to sell high. Since I'm in the US I'm going to convert that to dollars at the rate of about 1.5 which means that the MOST money you can hope to make on the arbitrage of low price to high price is $0.06

Now let us compare $0.20 per cycle of cost with $0.06 per cycle of revenue (again ignoring the fact that in reality nothing is 100% efficient) and we can easily see that this is a losing proposition. It'll lose AT LEAST $0.14 per kWh per cycle for the person trying to operate this arbitrage scheme as a business and they'll soon go bankrupt. Problem solved.

Now if the cheap power was $0.01 and the expensive power was $0.50 then they might be able to make money. But from what I understand of the power pricing, that's not the case.

If you'd like to continue to argue, please do so with actual numbers that mean something and/or are based on reality, rather than belligerent trolling. Please see this link where I previously did the analysis that you couldn't be bothered to read: https://news.ycombinator.com/item?id=9063702

Belligerent trolling? How utterly obnoxious.

You are inventing numbers from fantasy, and demanding retorts. What an astonishing bore, your inconsistent, incoherent point not in the least viable. Find a hobby.

The idea that some people fetishize disruption and heads-you-loose, tails-I-win situations baffles me. The utility has expenses beyond the cost of power generation. They don't exist to provide a subsidy to cool upstarts. They provide critical infrastructure for those cool upstarts and everyone else.

There are certainly a lot of perverse incentives and inefficiencies in the current model. Even so, its either ignorant, childish, or intellectually dishonest to act like it is outrageous that a utility has a simplified pricing model that doesn't accommodate the outliers among the outliers (residential customers with large solar and battery installations), or that their overall pricing allows margin for cost recovery and profit on power they deliver, whatever the source.

You can get energy out of a lithium battery several times, which puts it well ahead of tearing holes in the earth to mine coal.

No, it's not permanently "off the grid" as it depends utterly on the whole industrial infrastructure, but it not continually tied to the grid like a power line running to a coal-fired power station.


You can't get any energy out of a battery until you put energy in ... alas more in than out per the laws of thermodynamics.

Obviously TANSTAFL but the clear point here is you can burn coal only once. Solar panels + Li-ion can be reused atleast 500 times (assuming standard Li-ion batteries that crap out after 500 full cycles).

yeah no kidding. It would have been a diversion to mention solar; which Musk is also betting on, not co-incidentally.

Solar in similar: it depends utterly on the whole industrial infrastructure, but is not continually tied to the grid like a power line.

I wish sites would add automatic abbr tags to think like FWIW or, in this case, TANSTAAFL so those no in the know can easily mouse over and see what the hell you are saying.

"There ain't no such thing as a free lunch" from Heinlein's The Moon Is A Harsh Mistress, a highly recommended read.

Oh, I already looked it up. :) I was just realizing that it's not a hard problem to solve and sites could easily automate this, so they should. I guess you could argue that the browser could solve it as well. Or people could just write it out instead. :o

It's the kind of problem extension apis are really good for. I found this one:


It's most handy as a (weak) indicator of pomposity and / or libertarianism on the part of the user.


People Like to Make Up Abbreviations That Take More Explanation Than Just Spelling it Out Would.


Hahaha. I love how you end this with another one I had to look up.

Every time I see SMH (shaking my head) or MFW/MRW (my face/reaction when) or a handful of others, it makes me feel really old. If people didn't say it during a Quake match, it's not in my vocabulary. Darn kids these days.



Check out the google dictionary plugin for Chrome: https://chrome.google.com/webstore/detail/google-dictionary-...

You can double-click almost any abbreviation (or any other word) and get a definition.

"The big problem is the water...and it will run downhill from the Andes and wherever else Lithium is mined and into the Ocean."

Except for the geography which prevents that from happening and is why that area has giant salt flats:


I drove my Jeep across The Uyuni Salt Flats of Bolivia [1]- easily the most beautiful place I've ever been in my life.

The rumor is they're about to tear it up for a Lithium mine :(

[1] http://theroadchoseme.com/the-uyuni-salt-flats-to-chile-1

It's very hard to beat lead-acid on:

- $/Wh

- number of cycles

- ability to be recycled at eol

- loss of capacity over the lifetime of the battery (or beyond!)

- safety

It is easy to beat on

- power density

- weight

- maintenance

- mechanical stability (especially for fluid based cells)

- installation cost (lead/acid requires a sealed enclosure venting to the outside to get rid of free oxygen and hydrogen)

The same batteries that work well for automotive applications will not do that well when you're building a storage cell for a house.

Lithium-ion does not have a whole lot of edge over lead-acid deep cycle gel cells when it comes to stationary applications.

The biggest issue with Lead-acid is that if you don't water them (if you use fluid based cells rather than gel based cells) that sulfur bridges can grow between the plates causing a cell to be shorted out. Gel based cells don't have that problem and are common in deep discharge setups.

I'd imagine in this case they are looking at the economy of scale they'll be able to gain when producing these out of the gigafactory. I'd be interested to see the $/Wh cost difference once it comes fully online.

Tesla batteries retail for $30K@85KWh, so approximately $350/Wh, Lead-acid deep discharge is about $10000/100KWh, so approximately $100/Wh. That's a pretty large gap.

Keep in mind that $30K for 85KWh is pre-gigafactory and is also for a vehicle. There are many more safety factors involved in making a battery that is going to moving around at 70mph. Much of the cost of the vehicle based batteries, may be able to be skipped, if you are not as concerned with mobile safety and weight.

Fair enough. But the pros/cons of each tech would need to be balanced against the $/Wh cost. Once the gigafactory is fully online I thought I'd read they were shooting to drop the pack cost in half? If that were true then it'd be 175 vs 100 and the pro/con list would be much more important, right?

No, the costs are better expressed in terms of price divided by total KWh stored and subsequently recovered over the lifetime of the battery.

So even if they can get the 'installed' price down to < 30% of what it is today (some corners can be cut for stationary applications) then there is still another barrier to be crossed.

All in all this is extremely exciting because manufacturing batteries at this scale will surely lead to economies unseen before but Lead-Acid has an 80 year head-start and is very hard to beat when weight and density are not a major factor.

After all the one reason why we have Lithium-ion is because of weight and power density.

Laptop and vehicles have a lot in common that houses versus laptops and vehicles do not.

The Tesla Model 3 car, due in a few years with a fully online gigafactory, is supposed to retail for $35k I think. This certainly means that Elon is expecting a price drop in the (car) batteries by quite a significant amount - perhaps even down to a price competitive with Lead-acid for the (home) batteries discussed here.

Might want to check your numbers there. $10,000 / 100 kWH == $0.10 per Wh.

Which you absolute cannot get in any market. If you could, everyone would do it because the supply cost per kWh including replacement would beat regular power company power.

EDIT: Just went back over my old calculations for this. The basic problem is that you trade off against the cost of peak electricity, not your solar.

So you can essentially assume off-peak and shoulder power is used for charging, and then you use that to offset your most expensive period. The question is then "how efficient is charging" and "how many cycles do you get from the battery before replacement".

Even at $100/kWh, the math is a near miss rather then a clear win as far as I can tell still.

Too late to edit, that should have been KWh of course.

But presumably cost will be lower when the new factory comes on line right? Otherwise why built it?

perhaps this is where batteries that miss the tolerances for car usage will end up, like how chip manufacturers handle it

Energy density is a big one. To store 5 kW * 24 hours (barely enough to power my house's essentials), I would need 286 of these (http://www.amazon.com/VMAX857-Battery-Performance-minnkota-t...). They are not small. Also, that would cost me nearly $32,000 in just batteries.

My ideal setup for this would be something like 20 kW * 7 days. That would fill my basement pretty easily.

That's a very expensive battery for the given capacity. If you want to be efficient check out the gel batteries used to power golf carts and forklifts. You'll need 24 2V cells if you want to do this efficiently both from a cost perspective as well as to reduce line losses between batteries and inverters. (24 and 12V are really not adequate for larger power installations).

Such as these? http://www.batterystuff.com/batteries/golf-cart-products/

I don't really see orders of magnitude jumps in power/$. Or am I looking for the wrong thing?

No, more like these:


Sold in bulk. That's a 48KWh bank and it cost about $US 5K

This is roughly 2.5 times cheaper than the marine battery I found first, definitely not orders of magnitude.

This is $5k for 2 kW * 24 hours. So 3 of these at $15k total would roughly replace my $700 generator + $10 worth of gasoline for emergency situations.

To truly run my house where it would be adequate at 20 kW or 24 hours or so, I'd need 10 of these at $50k. To run my house of for a week (where I live, the last major power outage lasted three weeks), I'd need $350k. For that amount of money, I can just buy a very nice house in Florida and go down there when the power goes out.

Now, if I go top of the line, I can get a 22kW generator (http://www.homedepot.com/p/Generac-22-000-Watt-Air-Cooled-Au...) for $4,700 + gasoline at $2.30/gallon where I live. This will not even require me to go out and start the thing as it kicks on automatically, much like a battery backup does.

Battery powered houses just don't make sense cost-wise, and at this price disparity it's not a question of spending a little more: $350,000 vs $4,700. That's two orders of magnitude. It's not the clean option, but given that it's standby power, I'd rather see us invest in more efficient power plants (nuclear and wind) than home batteries.

I think you're more than a bit power hungry. My house consumed < 5 KWh max per day, so even running to 50% discharge that bank would power the house for up to 5 days.

It's much easier to save on consumption than to create capacity, especially stored capacity. You don't really realize just how much energy goes into AC, heating, washing and so on until you've lived off the grid for a bit. And then you'll quickly learn how to conserve energy. I'm currently living in an on-grid house, the old habits die hard, my computers are probably the biggest consumers here.

Anyway, if 22KW is your power budget then don't bother going off-grid without a generator.

Battery powered houses make perfect sense if you're able to conserve power, if you can't then of course it does not make sense.

That I suppose is the line for me. I am unwilling to go to a point where I cannot use my washer/dryer, dishwasher, AC, etc. I believe the majority of the developed world is with me on this, though of course there is a minority that have other priorities.

~30kwh is the national average for daily use. 120 is crazy high unless your blasting an AC or heat all day. At 12 cents a kilowatt hour that's a $438 monthly bill.

Even 30 is pretty damn high. For someone living off grid with a purpose built/renovated structure ~5kwh a day gives you quite a lot to work with.

True, but you want to be able to handle peak usage too. When 2 kW well pump kicks in, I don't want the lights to dim. AC is 3-5 kW and more to start, and so on.

Yeah, if your goal is to live off the grid to save the planet, that's a different story. Then the only question is how much will your Lithium based battery (mining, manufacturing, transport, recycling) affect the planet vs buying wind power from your local utility. If you want to do a little good and save a little money, putting batteries in your house is not the right thing to do. If you want to be independent of the grid in case of emergencies get a wood stove and a gas (or better diesel) generator. All around, I don't see where whole house battery backup fits into any scenario. I see data centers using these batteries, not residences.

I did the shorting current calculation on that battery in the pic elsewhere in this thread. The fuse was there for decorative purposes only, at those currents everything is a fuse, the one Ththing you really have to hope for is that it will douse fast enough and that there will be no air/fuel or H2/O2 mixture nearby. That's the main reason I built this pack into a little building (underground bunker really) of its own near the house but not so near that it would be a problem if it would break down.

The inverters were housed in the second half of that bunker so as far as the house was concerned nothing changed.

The whole system was capable of producing 11KW, two tandem 5.5KW inverters ganged to produce 240 V for well pumps and other large consumers (welder, plasmacutter).

It worked super good but you really had to keep an eye on the charge level when running big tools, the plasmacutter would drain the battery in about an hour.

But running the plasmacutter was the exception, not the rule so most of the time it was just powering a very low level of loads compared to most houses.

I really miss the system, and the farm it sat on.

That's the beauty of lead-acid- it has one of the best (if not THE best) surge currents.

For example, the ~70Ah battery in my truck has a cold cranking amps rating of 700A, or 8.4kW out of just one battery.

>To store 5 kW * 24 hours (barely enough to power my house's essentials)

So based on 5 kW average, your electric bill is… 3650 kWh/mo? That's about 4x the U.S. national average for a household (903 kWh/mo).

Is this correct, or is 5 kW an overestimation?

5 kW constant? Do you have the sauna on all the time?

For that matter, it's hard to beat the NaS battery


Its worth noting that with lead acid most people target a ~50% depth of discharge as batteries start getting damaged when they are cycled deep. (Yes even deep cycle batteries.)

Now that also provides some additional redundancy so it's not like the other 50% is entirely useless.

It looks like Elon wants to ramp up production in the new Gigafactory right away, and create home batteries from the excess capacity. A Gigafactory running at full capacity should bring the cost of lithium ion batteries way down. Electric cars haven't hit the mainstream yet, so he has to do something with the excess capacity, and this looks pretty straightforward.

So even if he sells these batteries at the break even point, he'll still get much closer to an economically viable Model 3, because the battery is such an expensive part in an electric car and this will bring the price of batteries down.

(I'm not sure if my reasoning makes sense though, because the Gigafactory isn't anywhere near finished yet, and according to wikipedia it won't hit full capacity until 2020.)

Home batteries have arguably fewer cycle times than a battery in a Tesla. By selling these, Tesla is essentially selling beta models to figure out kinks in the factory, in the batteries, etc, before putting them into their mainstream vehicles that have to suffer huge temperature gradients, lots of recharge cycles, etc.

If I recall correctly, battery production is currently a bottleneck for Tesla production and one of the major reasons why there is a waiting period of a few months after ordering. So I'm not sure to what extent he depends on home batteries to find a use for excess capacity, even if Model 3 isn't available yet.

What will be even more interesting is when he builds 10x the capacity of the Gigafactory, which he said he expects to happen in the future. At that point batteries should be completely commoditized and sold only slightly above raw material cost (which is great news for EVs).

Looks like they might finish the Gigafactory by 2016: http://www.hybridcars.com/gigafactory-could-open-ahead-of-sc...

I have home back-up power based on an inverter charging a lead-acid battery (located in a sheltered area outside the home), which costs about $100/kWh. Usage is about 1-2 hours discharge per day. No matter how well serviced, I've found these batteries don't last beyond four years. Hence I'd pay even $400/kWh for a well-engineered deep-cycle battery that is safe, maintenance-free, and will last at least 10 years. Excluding balance of system, even.

> No matter how well serviced, I've found these batteries don't last beyond four years.

Wow, that's really short, especially with such a shallow discharge pattern.

Not necessarily! We don't know how deep the battery is being discharged. But we can make a guess. 4 * 365 = 1400 cycles.


According to that chart (which is an approximation of course) 1400 cycles corresponds to about a 40% depth of discharge. Which isn't terribly shallow.

The other variable is the discharge rate, and the higher it is relative to battery capacity the worse the efficiency and also the propensity to fail early. A lot of times doubling the pack size can extend the pack life by more than two because the increased efficiency (the internal resistance is lower) reduces the depth of discharge by more than half.


Of course it feels totally ridiculous to only use 20% of the nameplate capacity of the system, and much worse than using 40% which you can sort-of rationalize as "half" but if it decreases your dollars per joule, it might be worth it.


I should also mention that if you're constantly charging and discharging and you don't mind a little energy loss you should look at nickel-iron batteries. They're not terribly efficient nor are they cheap in absolute terms but they're basically bulletproof.



I've wondered for years why people always gravitate towards Li-Ion cells when talking about a home storage battery. Li-Ion's advantages are far, far less important for a dwelling. Weight doesn't matter... you won't be moving them. Size doesn't matter nearly as much as it does in a vehicle... losing a few inches off an entire wall in a garage won't really be an issue for most people. Edison cells are incredibly durable and much, much more environmentally friendly than any other battery tech I know of. The lifespan is nothing short of incredible too... you won't need to change them out.

Thank you very much for the 2nd link. I was unaware any company was still manufacturing them. The last time I looked, the last company I could find that made them stopped a few years prior. I'm glad someone is making them still/again and marketing for an appropriate use.

The one odd thing is the price... for something as low-tech (relatively speaking) as an Edison cell, I'd expect them to be much cheaper. Must be the lack of competition.

They may seem to be low tech but the electrodes are works of art and manufacturing them is a lot more expensive than a lead-acid battery of comparable capacity. They charge slower too, but they'll stand up to abuse better than every other rechargeable battery tech. I looked at them for a long time before settling on regular lead-acid, cost and finding an inverter that would charge these properly were the major factors.

check out these _types_ of batteries.


no recommendation on the supplier, but funny thing, the power companies and telcos have already figured this out for reliable DC power :)

Thanks, good point about telcos.

Do we have any reason to believe lithium can achieve that? How long are the Tesla batteries supposed to last...?

What would be the advantage of these LiPo batteries over traditional lead-based batteries? In car's, I understand weight (and volume) are really important, but for stationary usage these seem way more expensive / Wh stored?

I think this is a very important question. In raw $/Wh lead acid wins hands down, so it might be due to other characteristics such as number of cycles that can be run, and peak load characteristics?

Here is an overview of estimated cost for various battery types, does not include LiPo however. http://www.batteryuniversity.com/learn/article/cost_of_power

Not a battery engineer (but my dad was)...

Pros: Higher energy density, so you don't need much room for the batteries. They don't emit hydrogen when being charged like lead-acid does, so you don't need safety ventilation.

Cons: Not as conveniently recyclable as lead-acid (there's existing infrastructure for this is already in place).

The site isn't coming up for me (neither is google cache) but I'm wondering it they went with LiFePo4 batteries - they have a gentler failure mode than some of the other lithium chemistries.

If you are going to count hydrogen emission as a problem for a lead-acid battery then you should be honest and point out that lithium batteries of all varieties have a habit of failing in spectacularly combustible ways.

Sorry - my last sentence wasn't dramatic enough. "Failure mode more like a fireworks factory burning, than the Hindenburg exploding"

Wait, are you using the Hindenburg as the worse outcome? Most of the people on it survived, and a 90 second fire is by no means an explosion.

Cars need tremendously high drain for brief periods to start the engine, especially under adverse conditions like winter when oil starts out being cold and less viscous. They also generally don't deep drain the battery. The ability to be optimized for those constraints plus their simplicity and low cost is why they still own that market. This is not my field, but I'm not aware of any battery chemistry that could conceivably compete with them, and because of their lead we'd like an alternative if there was one.

I'm also curious about their lifetime. My laptop batteries are pretty weak after three or four years. It's much easier to justify $thousands as a one-time purchase than $thousands/year. For many of its applications, this is going to have to beat a generator. Which, come to think of it, probably means that if they're pitching this as a way off the grid it is precisely because it won't be even remotely competitive with a generator.

You charge your laptop everyday. So it depends on how often you recharge them, which means it will depend on how big of a battery you'll buy. If you buy a 100 KWh battery (probably around $10,000-$15,000), I think that should last most Americans at least several nights to a week? So it might approach 10 years before it starts degrading, and then probably a few more years of charging it every day. I assume's Tesla's batteries will be relatively high-quality as well.

Isn't the idea that you keep it topped of and use it when grid power is expensive or missing? That usage pattern would involve multiple charge cycles, perhaps even 365 in a year. I guess it would actually follow the Tesla charging patterns fairly close as well. What is the estimated lifetime of a Tesla's battery?

If the battery has sufficient excess capacity, you can split it into multiple banks of smaller batteries, and cycle which ones you charge and which ones you use. Add a small computer and you can use whatever logic gives you optimal charging/discharge patterns to optimise for lifetime.

For a given generation of lithium battery cell and management technology, there is the option of trading off between capacity and durability.

Field-replaceable laptop batteries are engineered as a consumable, and runtime, weight and charging speed are given priority over long life. Laptops with integrated batteries make a somewhat different tradeoff, but still assume that battery replacement will be a maintenance expense for some users. In both cases, the expected average lifetime of the laptop itself is also a factor, which I'd guess would be about 5 years, max.

Packs for laptops make different tradeoffs vs packs for a car, or home power storage. From memory, based on some back of envelope calculations, tesla trades 15-20% of nominial capacity of the cells in their auto packs for >=4x or greater durability. Packs for home energy storage would probably make similar tradeoffs, and might get more life with less aggressive charging rates.

The 'living off the grid' angle is a red herring. The main application of this would be solving the peak load problem, ie smoothing out the load on power stations throughout the day. It is not clear to me how a LiPo batter is better suited for this than other battery types though, especially since weight is not a concern for a stationary battery in your home.

I wonder if this even needs to be something in the home. Wouldn't it also make sense to install these things, in bulk, in a place where they could service several homes? Say, at the block level. If it is part of power distribution infrastructure as opposed to a consumer product, then that simplifies some of the safety and maintenance issues; concerns like weight or volume are even less important if they are housed in a dedicated structure.

This is being done. Power companies have shipping containers full of batteries hooked up to their grids. I have read better stories but the first thing I found googling just now is this http://www.abc.net.au/news/2015-01-07/ausnet-trialling-new-s...

That's still a pilot program, though. The Wikipedia article has a good summary of various tech and installed systems: http://en.wikipedia.org/wiki/Grid_energy_storage#Batteries

Isn't part of the problem that production costs for batteries are so high? I suspect this is Tesla staking claim in a market that will grow as the price of large rechargeable batteries drops. And that price drop will in large part be due to Tesla.

Can someone explain to me why being able to build off the electrical grid is worth all this effort since you're still going to need running water, sewage, bins collecting, broadband and a number of other things?

I don't have water or sewage at my house. I have a well and septic system. I also have a propane generator but it's only for power outages, that happen more frequently when you live in the country. I do have a private company collect my garbage.

I live in the Ohio Valley, near Pittsburgh, so we get some of the lowest amount of direct sunlight in the US. I'm not sure if solar is viable in my area yet.

Water and sewage -- Most people in rural america and even in semi-suburban america already use their own wells and septic systems for water and sewage. Likewise with trash, many people drop their trash off at the dump/recycling center themselves. Broadband, yep, no DIY solution there but various forms of wireless internet are available that make it quite feasible to have a completely unwired home if not disconnected.

But still the question is, why would I want that? I'm all for distributed power generation, but it can still be optimized better when it's connected to a grid.

There are many possible reasons. You might enjoy the feeling of independence or self reliance that supplying your own power brings. You might be a weed grower and not want to be found out because of your energy bills. You may feel that it's more responsible to produce your own electricity and have a clear understanding of its environmental costs. Grid power may be unreliable in your area, or expensive. Maybe you think that power lines give you cancer. Maybe grid power is simply unavailable in your location.

All those are good reasons to also have your own power. You'll get your independence and might even save some money.

But even then it's still good to be connected to the grid. It will serve as a backup line and if you produce more enery than you can consume, you might be able to sell something back to the grid.

And THAT is a primary reason utility companies are fighting grid-connected consumer solar right now. If you are grid attached you are part of the cost of maintaining the grid that is normally offset by your revenue to the utility. If you are just using it as a glorified battery backup by feeding in excess during the day and pulling during the night and you are a net zero to then company then your per-customer revenue is much much lower. If only a small percentage of customers do this then you can level it out. If that percentage starts to grow then something has to give. Either you lower your maintenance budget, lower your operating costs, or lower your net profits. No one directly involved wants any of those to actually happen. This is obviously greatly simplified (e.g. The extra cost of handling customer generated power), but you get the idea.

Or you negotiate with whomever licenses you to be allowed to change your charges so that the maintenance is covered by a connection/subscription fee and usage is billed separately.

This is increasingly how utilities are structured in Europe: You have connection charges, and usage charges, and they may be due to different companies (though are often billed together via the provider you pay usage charges to).

This has come as part of breaking up utility monopolies so that people can e.g. pick "their" electricity provider (of course in practice this just means the providers settle overall relative supply between each other).

My utility here in the US has a per-custom base fee, but I think the issue is the base fee is regulated and not high enough to cover the costs of solar customers.

The "grid" doesn't yet exist in certain plots of land. One may want to build a house in the woods, but not pay the costs to get electric/water/sewage run to the property from whatever main road is closest.

The question isn't "why would I want that" it's more "given that I live in a place where grid hookup is $100k since I'm 10 miles from the nearest power line, what is my next cheapest alternative?"

Once the question is framed properly -- at least for a few million people in the US -- then the motivation for storage becomes much clearer. If you have a battery and an inverter then you hook that up and it feeds the house. And all your other power generation choices feed the battery. Solar, wind, hydro (if you live on/near a stream or river), small generator, etc.

If it costs $100k to get hooked up and then you're paying some fee for power every month it might make sense to buy the battery for $20k, buy a generator for $5k and spend $10k on a wind turbine and $10k on solar. That's $45k versus $100k which is a good chunk of change plus you can expect your prices to go down as solar panels and batteries and whatnot get cheaper, whereas fuel is only going to get more expensive.

Even with a grid connection, this would be useful as it would allow the power companies to generate more during off peak hours. A distributed power storage solution combined with a centralized power generation solution would be extremely efficient. It's like turning your home into a hybrid.

And fail hard too - blackout (then brownout) are more and more a concern. Then there's the question of the power price. I don't think the battery will be cheap when revealed, but after a while, they will and help us with solar/wind created energy.

> And fail hard too - blackout (then brownout) are more and more a concern.

Maybe I'm just spoiled by the German power grid. As far as I can remember I only a single blackout of 30 minutes in the last 15 years (some time around 2008).

Arguably with money cheap at the moment, it's a good investment.

(One must still be cautious - even with 0% interest rates - since the principal is still repayable. If your part of the economy goes bad, a default on a 0% loan is just as bad/likely as a default on a 5% loan.)

It's an independence thing. If that isn't important to you, none of this is going to seem terribly useful.

Well. Broadband is available wirelessly either via cell, wifi, or satellite, so there's not a requirement for a physical connection. Water and sewer have localized options with wells and septic, but they are also extremely inexpensive to build and maintain and have a relatively small environmental impact.

Electricity, on the other hand, has no viable localized option today. It's also the only one of these that has a significant drop in efficiency due to the distribution itself and has a significant impact to the environment.

Local power storage means that grid can balance the load between peak and non-peak times. Also, local power storage means that wind/solar now has a solution for time where power output is reduced.

Having a battery that can power a home for a week is huge, if it's affordable. This could significantly reduce power generation costs.

significant drop in efficiency due to the distribution itself

This is usually less than the efficiency drop involved in a round trip through a battery. It's not as big a factor as you think.

I'm not just talking about electrical loses, though that is a factor. Having to build 2-3 times the capacity because power generation can't be distributed throughout the day is a huge inefficiency.

Having to build 2-3 times the capacity because power generation can't be distributed throughout the day is a huge inefficiency.

This seems to me the big benefit here -- enough penetration of home backup batteries means public power generation doesn't have to be built up to provide massive peak surges. Further, trickle charging the backup batteries during the evenings/nighttime and allowing them to meet some needs during the day also means a higher net usage of generated power, so perhaps levels of generation could go down altogether.

There's also then the capitalistic angle -- if you want more peak power at your house, you can buy more batteries in lieu of (or in concert with) installing secondary power systems.

But reducing gross energy production due to higher net utilization would be a really cool thing, so long as the total cost to the macro system (considering full life of the battery vs. load taken off power plants) is a net positive.

Even 'better' is that most of the on-demand generation is coal-fired plants.

From the research I've done on solar power systems (for powering homes) the market does not have an obvious pre-packaged solution that is made for storage of excess capacity generated by your solar panels.

One commonly suggested (and substantially cheaper) option is to just set things up so you don't have local battery storage and just redirect all excess power back to the utility company.

The problem with that has already been mentioned. You're giving power back to the utility company at a fraction of what you purchase electricity for.

But beyond that, as power requirements in appliances / computers / electronic gadgets continues to decrease, and efficiency and capacity of alternative energy solutions continues to increase, there will likely come a time (in the not-too-distant-future) when there will [at least in theory] no longer be a need for utility companies.

In fact, from varied sources online I've gotten the impression that many countries (besides US) have substantially reduced power requirements per household where even today it's feasible (for those with sufficient roof space) to move all of their power usage off grid, and rely strictly on power generated by solar.

> The problem with that has already been mentioned. You're giving power back to the utility company at a fraction of what you purchase electricity for.

That's not a problem, that's how the markets work. When electricity is abundant (i.e. sun is shining, wind is blowing), it's cheap; when it's in demand (in the evening, after the sun and wind stop but people want to cook and watch TV), it's expensive.

The problem with energy storage isn't just a home-problem, it's a network-wide issue. AFAIK, current batteries aren't really able to solve this issue, in the long-term (i.e. considering the lifetime and replacement of the battery).

"You're giving power back to the utility company at a fraction of what you purchase electricity for."

Not if your region was forced to subscribe to a feed-in-tarriff subsidy scheme for solar. Around here, there was a time when solar generated power earned 10x the value of the same amount of energy purchased from the grid. That multiplier has fallen thankfully, but is still greater than one.

Those batteries can come in useful even when you're still connected to the grid.

Right now, some locations have laws and/or regulation that force grid companies to buy solar-generated electricity from home owners at fixed rates. This makes a lot of sense right now as a measure to encourage the adoption of solar, as a way to get off fossil fuels. In the long term, it might become a less useful measure, and we might want to allow market mechanisms for time-of-day-based pricing. This is already happening on the big players' market, where you see drops of the spot price of electricity at noon on sunny days. Extending these market mechanisms to individual homes makes sense, as long as home owners are empowered by technology to make use of it.

A large battery is an important piece of such empowering technology (combined with being able to set a smart policy for when to run off the battery, when to run off the grid, and when to feed back into the grid).

Think of it as a CDN for energy.

The grid will become less reliable over time as utilization increases, and in many cases we have fundamental limitations that make broad-scale robustness difficult to implement.

So fake it out. If I have a reliable local power source, I can easily take short outages without user impact.

I get water from my well, have a septic tank in my backyard and use a 3G connection (there is no landline connection available where I chose to live). Getting off the electric grid would be nice, not to mention it would be cheaper too!

I note that people replying to this are saying that you can avoid those things (if you live sufficiently rurally, which is only true of a fraction of the population), but not really saying why you'd want to.

Here in Scotland it's the other way round. Orkney is detached from the grid and trying to get itself connected, so it can better balance local renewable generation with the rest of the UK (and thence ultimately the European grid as a whole). Maybe they'll go to municipal batteries but the cost is still not attractive.

Not sure most of those need physical connections. We can drive our garbage to the dump and also compost. We could dig a well, and we have a septic tank. We could get satellite internet. Physical connections for electricity is about the only absolute, unless you go solar, but then there's not a good storage mechanism for cloudy days (from what I can tell).

I don't see the big benefit here being living off any grid. To me, the benefit could be to charge battery when electricity is cheap, and also - if the battery is portable - to easily get a power source places where there is none.

I've always been wondering why there have never been affordable local power storage solutions on the market.

I'd love to have a battery like this to store excess power from solar panels. Returning power to the grid is a waste in both efficiency and money (you just make the power company richer).

Unless you live in Germany (where there are laws forcing power companies to buy excess energy back against peak price), a battery should be the way to go.

I guess the big questions are,

- How do battery charge/store/discharge efficiencies compare to transmission losses?

- How do capital investments to support returning power to the grid compare to the cost of batteries?

One thing I'm fairly confident of is that just having batteries (without solar panels) to do peak-flattening temporal "arbitrage" can't make economic sense. If it did, power companies would do it themselves and keep the profit.

> One thing I'm fairly confident of is that just having batteries (without solar panels) to do peak-flattening temporal "arbitrage" can't make economic sense. If it did, power companies would do it themselves and keep the profit.

They're trialling that right now in the UK: http://www.itv.com/news/anglia/2014-12-15/power-boost-as-big... http://www.edie.net/news/6/Smarter-Network-Storage-Energy-ba...


Because so far batteries have been improving in cost/Ah only very gradually? And generated grid power from fossil fuels has been historically cheap?

>Unless you live in Germany (where there are laws forcing power companies to buy excess energy back against peak price), a battery should be the way to go.

You can get power companies in the US to buy your excess energy. The co-op that supplies my power will set up a meter if you have your own power source. If your total usage is less than what you created they will buy the power from you (not the best rate).

They will even give you money back for installing solar cells [1].

1. http://energy.gov/savings/cobb-emc-solar-rebate-program

> Unless you live in Germany

Not anymore. The price you get from your power company has been consistently lowered over the last years, now you only get about half of what you pay the power company for the electricity you use.

The UK also pays domestic solar producers for feeding in to the grid - it also pays for the generation as well.

> Unless you live in Germany

Many populous U.S. states have net metering, New York and California inclusive.

Like many others, I've lived on solar power (no grid, no generator) for two decades now. No problems, no fuss.

In rural areas, wind powered battery storage was commonplace 100 years ago.

Perhaps if you bothered to do a little research....

I'd love to have a self-contained electrical system for my house. I'd preferentially wire my home with a DC grid alongside the AC, but there's no standard. Do I run 120v, 240v, 5v, 12v? Which interface do I use? Barrel connectors, USB, cigarette lighter? If we have a large-scale movement to household DC, we'd have these things hammered out without me rewiring every appliance.

If these obstacles were overcome, almost everything in my house could run on DC. Most stuff either converts to DC internally, or doesn't care.

There are standards, many of them, just as there are many different standards for AC power worldwide. Your DC system design will be governed by practical technical considerations in concert with economics. The physics of low-voltage systems are such that they are viable only when current is low; otherwise, a 5V or even 12V system will require prohibitively expensive heavy-gauge wire in order to provide the proper voltage at the point of use. So modern DC systems are typically all 48V or even higher now (people are building solar systems with system voltages of 600VDC!). That does not mean you need to run those higher voltages within your home, but from a practical perspective you probably want either 24V or 48V unless your house and/or current needs are very small. To figure this out, you need to consider the following:

- What devices do you need to supply? Often this is the true governing factor although switching regulators are very efficient and inexpensive up to a few amps. - How much current do you need to supply to a particular location (this depends on the power consumption of what you're running)? - What is the distance from the panel to the point of use? The longer the distance, the greater the voltage drop across a wire of a given size (and the higher the cost of larger wire).

As for connectors, there are only a couple of sensible answers. USB is fine for 5V/1A needs, but you're not going to want to run a bunch of 5V wiring separately from the higher-voltage wiring you're going to need anyway. The proper approach here is something like http://www.powerwerx.com/adapter-cables/usbbuddy-powerpole-1..., which will happily work in either a 12V or 24V nominal system. You can of course make other power supplies from all-in-one ICs like http://www.mouser.com/ProductDetail/RECOM-Power/R-78W90-05/?... and a small project box; larger currents and other voltages are available too, of course. These make good replacements for wall warts.

But you don't want to be wiring any of that in your house; instead, you want to use Anderson Powerpoles in a single-voltage (probably 24V or 48V) system. They are properly rated for DC use at these voltages and plenty of current (up to 350A if you need it, which you won't). They can be installed in blocks of 4 2-blade connectors in standard wall boxes, with neat, professional plates. They can be easily crimped onto appropriate-gauge wire by amateurs. They are code-compatible and safe, unlike the dangerous practice of using receptacles designed for 120VAC or some other existing local/regional standard. They provide a reliable connection and reliable disconnection, and if crimped properly they will not fray, crack, or loosen within a very large number of connect/disconnect cycles. The other low-voltage DC "standard" that is popular, the barrel-type "cigarette lighter" connector, provides only 7A at 12V, is bulky, and does not offer a reliable connection. While it is popular in automotive applications, more serious users of DC power -- the Powerpole is very popular among amateur radio enthusiasts -- avoid the barrel type connectors for these reasons.

The only real decision to make is whether to use 24V or 48V, which will depend primarily on the questions I noted above. Higher voltages are certainly possible, but watch out! Switches rated for higher DC voltages (especially at currents much more than 1 or 2A) are hard to find and expensive. Your standard "AC quiet switch" that you can buy for $2 at the local hardware store is rated for 125V AC ONLY. It is not safe to use with any DC system, although in practice it's probably acceptable for 12V systems at a hundred milliamps or so. For more practical applications, you will need to be sure that your equipment is equipped with proper switches, or no switches at all; you will also need to make sure that any hard-wired DC circuits (such as for lighting) are properly switched. Where you have flexibility in the voltage accepted by your equipment, you will need to trade off the higher cost of switches and other passive components at higher voltages against the higher cost (or voltage drop) associated with wiring at lower voltages. You will quickly learn to read spec sheets and rating stamps carefully when you work with DC.

The last thing I'll mention is that you may not really want to do this. At my location, there are often several months with extremely limited power; even the inverter's 25W base consumption dictates that it be on an hour a day or less if at all possible. For that reason, anything I have that needs smallish amounts of power continuously (such as a freezer, reading lamp, phone charger, etc.) gets DC. But in general, it's simply more convenient to use off-the-shelf devices. I can and do make my own power supplies, but I don't really want to go re-power my laser printer or table saw (which by the way has an AC-only induction motor in it). For higher-power devices, off-the-shelf is the way to go; it's much cheaper and the inverter's overhead is amortized over a lot of consumption anyway. If you have a larger system that can easily supply 100W or more on an indefinite basis, you probably don't need to bother much with DC; it'll be easier to just leave the inverter running all the time. A DC-powered well pump or freezer might be worthwhile, but I wouldn't go converting anything else. Most people are putting in enormous (to me) solar systems now; 10kW is common. With a system that large, you'll probably be fine even if it's overcast. For reference, I have 700 watts, and with endless stretches of 6-hour overcast days in winter, DC is the only way to fly. But your needs are likely to be very different indeed, especially if you have (as we're discussing here) adequate storage. The days of custom-wired 12VDC off-grid living are basically over unless your budget is extremely limited.

My budget isn't limited, so that's not a problem. I'm an electrician, so this would be a project for fun. But I know if residential DC became a thing, this would be so easy. I think we'd all be better off with residential DC and solar panels.

Sure, Musk makes it sound sexy, but do we really need to use Lithium in a stationary application? I'd probably be happier with a battery that weighs twice as much but costs half as much. Those might not be the exact tradeoffs, but that's the general idea.

However, I don't know much about the details of battery technology, so I could be completely wrong. If traditional technologies such as lead-acid were up to the task, then someone would have already made a big business out of using them. Does that make sense?

Lithium batteries are not only lighter, but smaller. The typical home today to go off grid in the U.S. is a tiny house or a motorhome. The reason is, it's very cost prohibitive for the amount of power you need. Batteries are the most expensive part of that equation. If you live in a 3000 sq foot house and run a $250 per month electric bill, it might take 50 $130 golf cart batteries to power your house for a day or two, and you replace them every 4-5 years. Or you could go with Iron Edison batteries that should last a lifetime. They are equivalent to about 4 golf cart batteries, and the only requirement is to re-fill them with liquid. They cost about $4,000 each, and are yet still very heavy. The lithium batteries will take up about 1/5 the size and even less weight, and should last much longer than the golf cart batteries, but not as long as the Iron Edison. But space and weight requirements down so much will bring down costs with overseas shipping and trucking bills to a minimum compared with the alternatives. Think what great success in small batteries has done for cell phones. Not that your home needs to be mobile, but I see cars with solar panels and homes with solar shingles... both always charging.... as a great use of the sun as an energy source.

Is that $4000 figure for the 12V battery made out of 800Ah 1.2V cells, rated at "400Ah @ 5hr, 450Ah @ 20hr" shown on their web site for $3880? I've always wondered why more fixed site solar PV systems do not use iron nickel technology; it it is initial cost, I wonder what makes this technology so expensive.

Some day I want to look into the feasibility/advisability of a continuous automatic feed of distilled water to keep iron nickel batteries constantly topped off, and a hydrogen outgas capture mechanism (preferably passive) which takes that output of the iron nickel batteries and feeds it as the input into a hydrogen cell.

The question is: Will it be new battery just for homes or will it be a recycled/repurposed battery from 'old' Teslas?

It think it will be the later one. Elon is just thinking ahead. There is nothing really new in this story. Everything is just made up. It is quite accepted within the industry, that when the car battery has a capacity of less than 70% to 80% it needs to be replaced. But what should the car company, in this case Tesla, should do with battery? Of course, it will be re-packaged and as such repurposed for other use. What other use case is there? The other use case is Solar, especially as his friend runs a Solar company. What in incident.

Could someone please fix the truncated title? My editorial advice would be to just cut from the semicolon.

Have Tesla solved any of the problems that have prevented people from selling large storage batteries in the past?

A big issue is that you don't get that many charge cycles, especially with lithium-based batteries. So, filling up the battery with solar power during the day, then running your house from the battery in the evening, will soon fall to pieces if the battery doesn't last a decent number of years.

Awesome! and great news for the renewables.

Right now, if there's a storm or what have you you can lose your heat, your power, your water - everything. Its a bit like the mainfraime/terminal days - everything is centralized, and represent single points of failure for the citizens it serves.

But with energy you create yourself, and things like water recycling or indoor farms, we could go fairly far in self-sustaining units. And instead of the grid, there could be local community sharing so if your power/water goes out you can pull from a local grid. It doesn't need to be in every home, but something more distributed means more resiliency in the system overall, and thats handy in a lot of scenarios.

All that's a ways away though - but making the energy storage better / cheaper is an important step.

But I'm curious of the environmental factors in battery production / lifetime / recycling, can anyone comment on the impact these batteries represent?

In addition to doing things like storing any excess solar power you might have, it could also be used to charge up at night on off-peak rates ("Economy 7" in the UK) and release during the day to reduce your peak rate electricity consumption - whether it would be financially worthwhile to do so would depend on a number of factors.

When will homes be built with sensible electricity distribution? So often they put the breaker panel in the basement. I want a small utility room or closet where I can install inverters or this battery. I want to be able to run 220V to my stove, laundry, garage (car charging), battery storage, and AC relatively easily - none of these is in the basement (except the laundry in some home I've lived in). Also, if a basement floods, how is one supposed to go down there to access the panel without risk? And it's darkest down there too. It just seems to be the stupidest place to put it. What's up with that?

What's up is that most people don't want a big breaker panel in a room they spend time in. It's ugly.

Sticking the panel in a closet doesn't work, because it generally violates codes twice, once for the fact that all the clothes/random junk in the closet blocks access to the panel, and a second time for the fact that even empty, most closets don't provide sufficient clearance all around the panel to meet code requirements.

If I were building a new house, I'd consider putting the panel on the main floor and just hanging a big painting to hide it (which still violates code, but it's pretty trivial to take down a painting).

Seems like just yesterday [1] I was saying they could do this if they wanted to. :-)

The first challenge is to make the operational cost of a solar + battery system less than the cost of buying your power straight from the grid. The second is to include capital costs in that calculation and still come out at break even or ahead.

[1] https://news.ycombinator.com/item?id=9055177

It will be interesting to see the market reaction to this regarding the value of electricity generation companies.

Governments that lean too heavily on taxes or state run monopolies for energy generation should also be concerned. There are places that tax generation from sources like the wind (for example, Nova Scotia), so I wouldn't be surprised if we see solar tax appear.

Thinking about it, why wouldn't utilities jump at this and make it a standard part of every install? It would allow them to lower the demand-based generation due to every house having a local buffer of storage. They could easily monitor the levels on all the packs in a sector and know ahead of time when they are going to need more capacity which they can fill with better generators like gas turbine or nuclear.

I disagree that the long term storage stationary storage is extraordinary, at least from the individual home standpoint, it does have great utility application (for windfarms/hydro/etc) and likely would help some businesses offset day time surcharges by charging storage at night.

Still for home use, I would prefer a large lithium pack to be outside my home.

This still doesn't solve the essential problem with these batteries:

They're about $20k each, and they only last about 4 years.

The Model S 85kW battery pack is estimated to cost $12,000 and is estimated to last 10+ years.

The SolarCity Battery field-test uses 10kW Tesla batteries and is leased for $1,500 upfront and $15 per month. So, if the batteries degrade, it's Tesla/SolarCities responsibility to fix or replace them.

The Gigafactory will likely reduce costs significantly.


Essential problem solved?

The list price for that pack according to these people is 44k.


It looks like you drank the tesla dealers coolaid:


Bad luck.

This clearly states that the cost for a replacement 85kW battery will be $12,000.


"We have received many requests for a Battery Replacement Option. We are happy to now offer this option for all three battery variants. This option will provide you a new battery anytime after the end of the eighth year at a fixed price. Prices are as follows: $8,000 for the 40 kWh battery, $10,000 for the 60 kWh battery, and $12,000 for the 85 kWh battery. You will be able to purchase this additional option through your MyTesla page in the near future."

I can't imagine that they would raise the price by 4 times. Where is the source for the $44,000 listed on the article you mentioned?

If there are 7,000 18650 batteries in a Tesla S battery pack and it's reasonable to assume that Tesla can produce (Gigafactory) these for $1 then the $12,000 seems perfectly reasonable. The current estimate for the cost of 18650s for Tesla is less than $2.

It's already been stated that the cost of a battery pack is less than a quarter the cost of the car, so the $44,000 is nothing but false. http://www.technologyreview.com/news/516961/how-tesla-is-dri...

Yawn. I've been following this concept, and a wide array of very talented scientists working on it, for years now.

Any of the below projects, should they ever see the light of day (you'd think out of this many, at least one will make it eventually), stands a good chance of being quite superior for this application in just about every way:







Very rarely the best solution wins.

Agreed. Also, which definition of 'win' is agreed upon here. Win by efficiency? Win by market cap?

Edit: hint, look out for the very talented marketers

Today I went to pick up two 100AH lead-crystal batteries for a long-run UPS (we now have regular load-shedding here in South Africa). If I believe all what I have read about them online, they are amazing, compared to lead-acid. Crazy heavy though (33kg each).

I see 'em audiophiles drooling over this.

just look at this homemade battery in some audiophiles basement:


Tesla could offer an "attachment" to their cars that let them serve as a home battery when parked.

You'd have to let it charge up before going driving, but for home owners who don't drive much, that could be very cost effective.

Unless I'm missing some complication?

Batteries have a limited number of charge/discharge cycles. If you use your car to power your home you'll have to replace the batteries that much sooner, at a cost of $thousands. Electric car buyers are paying a premium to have the batteries be mobile, better to use them for that application.

Wonder how this would compare with Bloom Energy Server[1]

I recall Apple made some purchases or investments in these products.


Why is living off the grid the main objective here? I live in a suburban area that occasionally has power outages. Right now I'm considering the purchase of whole house generator but if I could have a battery instead I'd do it.

You can have a battery instead. You can get a battery right now; lead-acid will work just fine, if we're talking power outages of an hour or less.

House-sized UPS systems are a thing. An expensive thing, mind you, though I don't know how expensive.

Yeah, I looked into that and last I checked it is prohibitively expensive. If this is a viable alternative I can see two great uses.

1.) Whole house UPS 2.) A way to take advantage of significantly lower night time electric rates.

Maybe having a battery pack like this at home would mean you could recharge your Tesla car much faster as you're not limited by the grid supply to your home? A bit like having your own Supercharger station at home?

We could have used this last week. A pole was damaged (I don't know how, just that it was damaged) and in the middle of a sunny day we lost power for 1.5 hours. Really looking forward to this technology.

What puzzles me is the timeframe presented. What is the point of starting production in 6 months if the gigafactory is not up yet, and TSLA is production constrained just making the car batteries?

The last piece for a wind-solar future. Ok, if this really comes to the market and can store 12-24 hours of a typical household consumption, we may be able to live off solar and wind.

Are orange and red terminals confusing to users? (I'm an electronics noob, maybe this is a convention)

Does anyone know if these could be a feasible energy store for people living on the Moon or Mars?

If we were able to create individual or community power grids; imagine how much infrastructure could just be removed. Maintained by the individuals owning it, instead of these stupid power companies and the way they work now.

We have all lived through the improvements in construction with tools that don't need to be plugged in and phones that are unplugged. The next logical step is homes that are unplugged and self power generating. There is an incredible gap in society in the U.S. created by the tax code whereby if you make $25,000 and are a family of 5, you receive enough tax and food benefits and medical insurance to be equal to the person that makes $65,000 per year. And if your income increases to $45,000, you will be losing money, so there is no motivation to reach that point. The Living Off The Grid topic has gone viral because those stuck in the gap seek a way up without increasing income, because it's hard to increase income without hurting oneself. But the idea of downsizing and saving up has become popular with it. Getting a little plat of land and a trailer or a tiny house for a time while saving up.... growing food, having chickens, all are ways to save up and gain without actual cash income increase. Adding solar power to the mix helps prevent power bills. It is also a terrific way to fire the local monopoly power company, who may or may not in your area have any decency of customer service. Without competition, why would they have to care. But the off grid movement is pulling the carpet out from under these government allowed monopolies and forcing competition. In the same stroke, it removes the tax burden from the homeowner that was included in the electric bill. If you have a solar or wind power system and charge your Tesla car too, then you have a completely tax free energy system. It sounds like it's taking away from the government, but the neat thing is, this can also be used to alleviate financial strain on the government. If you can provide a self powered mobile home with rain-water collection to section 8 housing, then the government is also saving on those utility expenses. And land is cheaper a little further out. I recently bought 10 acres in Creek county Oklahoma. The power company wanted $10,000 to add one pole into the land and connection. I opted that it was better to spend that money on a solar power system. The same was true of water with huge expense, so I opted for rainwater and later to add a well. The up front costs associated with being on the grid for many rural areas, or adding more power poles is really more than costs will continue to be as they come down down down for self power generation. This is all exciting to me. We have to consider total impact. Hydro power is still a hugely terrific producer of energy. Rain that fills the lake.... the lake is a battery.... stored to produce energy. So rain makes our energy. This is still a much better solution than building batteries for large power needs. Yet the infrastructure and labor required to put in poles and wires is too high for homes in light of these modern developements. I look forward to an exciting and bright future. ~David Webster Offgridquest.com and Facebook's Living off the Grid

Go go Musk you bloody champion. If we can harness the sun, waves and wind and store it in batteries, and perhaps making those batteries is bad, it's a better solution than continually burning fossil fuels that are destroying our forests, species, economies, and faith in humanity. I say keep doing what you're doing (unless I'm proved wrong).

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