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Show HN: Build A Personal Power Plant for $200 (gridlesskits.com)
373 points by nikodunk 40 days ago | hide | past | web | 103 comments | favorite



Here is the much more portable and expensive version of this kit.

Anker PowerHouse to store the energy. 400 WH which is about the same capacity as the deep cycle battery listed, but this is lithium based so it's much lighter (9.3 lbs vs about 30 lbs for the deep cycle version). $500 https://www.amazon.com/Anker-PowerHouse-Generator-Alternativ...

Foldable 80W solar panel. $190 https://www.amazon.com/ALLPOWERS-Foldable-SunPower-Technolog...

Extension cord for solar panel to battery. $8 https://smile.amazon.com/gp/product/B00FTFYH0U/ref=oh_aui_de...

Evaporative Cooler instead of building your own. $112 https://smile.amazon.com/gp/product/B007SNQ4FM/ref=oh_aui_de...

$810 for the total package. The benefits are that you get to use a lithium-based battery which is 20 lbs lighter, you can use a foldable solar panel which is more portable, and you buy a pre-assembled evaporative cooler which has nice features like swinging. Mainly this is a good solution for those that just want to press buttons and set up their configuration in a few hours otherwise the kit seems like a good option too.

I used this configuration at burning man and the battery was permanently charged even with the cooler on the whole time. I needed another shade structure for the tent to keep it down a couple more degrees but I was able to sleep until noon with this set up and be totally off grid and have enough power left over for lights and music.


FYI, I've seen prices for the Anker Powerhouse in the $300's on Slickdeals: https://slickdeals.net/newsearch.php?src=SearchBarV2&q=%22An...


Is there a major difference between lithium and deep cycle lead acid batteries with respect to battery life versus amount of discharge per usage or is it a wash?


There are indeed several major differences. The first one that comes to mind is to get the most cycles out of a lead acid battery, they recommend not discharging it below 50% capacity. Lithium ion batteries are usually good to 85% - 90% discharge.


And on the other hand shouldn't be fully charged. Only going to 90% capacity does wonders for their lifetime.


Yes, but you're still talking hundreds of charges to 100% for a Li-ion before you lose capacity. A regular charge to 90% and then only charging to 100% on the odd occasion you need the little bit extra gives you the best of both worlds.

Do even a handful of deep discharges on a lead-acid battery and you'll kill it.


How do they compare on temperature ranges?


Like you, I built a similar system for BM this year, but based it around two 48v Li-ion ebike batteries (550 Wh and 1000 Wh).

BMSBattery (China) sells a 48v 30AH Lipo battery pack [1] for $530 + $120 shipping, with delivery in 2-3 weeks. That's 1440 Wh! And the battery includes a "BMS", circuitry that prevents under/over-voltages, over-temperature, cell balancing, and allows for simultaneous charging and discharging. This last feature is really useful if you are using the battery with a solar setup and want to be able to source loads bigger than your panels can supply from time to time.

If you need batteries ASAP in the bay area, you can get similar products from AA Portable Power Corp / Batteryspace.com [2] located in northeast bay (caution - these do not include BMS so no simultaneous charging+discharging).

So, if you are spending $500 for the battery, you can get much higher capacity (Wh) Li-ion batteries around the same price point from suppliers serving the diy ebike market.

Caveat is that these batteries are typically in the 36-48v, so depending on your application, you may need to add a buck converter (to regulate voltage down to 12v or 5v) or a boost/ac inverter for 120v. Sometimes having a higher voltage can lead to some efficiencies vs lower voltages - can use thinner wires, less power loss over same wire lengths, voltage converters / inverters may be more efficient.

"DROK"-brand voltage converters are around $30 on amazon[3].

If you want to charge your 36-48v Li-ion battery, try the $38 MPT-7210A "Docooler® MPPT Solar Panel Battery Regulator Charge Controller 10A"[4]. If you have two ~20v panels, wire them in series so the panel voltage going to the charge controller is ~40v; it won't have to work as hard to boost the voltage for battery charging and will be more efficient.

[1]: https://bmsbattery.com/ebike-battery/715-high-power-48v30ah-... [2]: http://www.batteryspace.com/lithium-26650-battery-pack-50-4v... [3]: https://www.amazon.com/s/ref=sr_nr_scat_10967761_9119938011_... [4]: https://www.amazon.com/gp/product/B01HCL7LEW


What did you do with that much power? Did you go for the AC or fridge?


We added a pedal-assist ebike motor to our camp's quad bike (2x2 tandem; 4 passengers).

The high Ah capacity was to support using the motor and accessories (atv soundsystem, lots of "dotstar"-style LED strips) periodically throughout the day and night.

We had two batteries and two sets of solar charging systems: a large, heavy 270-watt panel at camp and 2x 100-watt flexible panels for the bike.

Bike panels extended the range of the bike through a combination of powering accessories during the day, recharging the battery (when not using the motor), and reducing the load on the battery by providing supplemental power directly to the motor controller (when using the motor). "750" watt motor, ~200 w of solar, so not really possible to drive without also using the battery.

Meanwhile, the spare battery is charging at camp and also available for light loads like phone charging and some lights at night.

Every day or two we swap the batteries such that the bike has the more fully charged one.


This got mentioned under another comment but it is worth stating at the top level: always use fuses or breakers in any kind of system, that battery is a fire/bomb waiting to happen if there is a dead short. Charge controllers can do this when they fail (I had a 30A MPPT CC do this, and not a cheap one). I wouldn't sleep next to this thing without it (I didn't look in incredible detail at their site but a cursory search didn't find anything about current protection).

DC systems and AC systems also require differently rated components. You cannot just go buy a 30A 120V AC breaker from home depot for the DC side of your system. It takes a lot more to disconnect DC than it does in AC (because AC cycles to 0V 60x/s it doesn't take much of a gap/insulator to break a connection, DC is not the same. Trying to use a light-switch for a DC light can result in problems [1].

I've had good luck with midnite products (charge controllers and breakers, etc) [2]. Their breakers are 100% rated in that if you expect your max current output to be 30A DC (12v probably), you can use a 30A breaker and not have to oversize it, they are rated to take the guess work out of how to size your breakers which is nice.

Edit: I tried to find some info on the CC they use (in case it had internal protection which I wouldn't trust even if they said it did) and no luck. Given its pedigree and price (most charge controller add on displays cost more than this thing) you definitely don't want to take any chances. Price doesn't always mean quality but there is probably a good reason they are usually more expensive than this.

[1] http://blog.gogreensolar.com/2015/02/ac-vs-dc-breakers.html

[2] http://www.midnitesolar.com/products.php?menuItem=products&p...


I figured this to be some rinky-dink setup with some teensy pocket solar panel. I mean, $200? Hell, a decent 100W panel will cost you that much.

100W panels are $94 now? Holy crap, if we used more power boondocking I’d cover the roof of the camper with them. But we don’t use the power we make now, with a propane-powered refrigerator and LED lighting. And that’s the problem with solar, it can power the little stuff, like LED lights or a small invertor, and 100W panels are almost overkill. But get to something like a fridge or A/C for even a small camper, and one will need multiple panels and a big set of batteries.

Nice setup, and I wish them well with their turnkey solution.


Solar panels are incredibly cheap, now. If you buy them by the dozen, you can get them for just 49 cents per Watt nowadays from places like renvu.com (no affiliation).

Spot market for PV modules is as low as 28 cents per Watt. Just the cells are as low as 20 cents per Watt. pvinsights.com (These are before tariffs, I think.)

We're in a very different world from when dollar-a-watt (at the cell level) seemed like the holy grail.


They mention a swamp cooler in the article, which is surprising. I would expect those to have a big power hungry fan motor that's too much for the panel.

They do say it's a DC based swamp cooler. Looks home made though...more detail on it would be interesting.


> They do say it's a DC based swamp cooler. Looks home made though...more detail on it would be interesting.

Called something like a "Burning Man Bucket Swamp Cooler":

https://eplaya.burningman.org/viewtopic.php?t=33842

Simple and cheap to make; the problem with swamp coolers at Burning Man is the dust. Eventually the water turns to mud, and the pads get caked in it. Plus, you have to carry enough water not just for drinking, but to run the cooler too.

But that's at Burning Man - in other contexts it works as well as any other similar cooler.


After a relatively blistering summer here in Seattle, here’s something I’ve considered building for when we leave dogs in the camper: http://www.mdpub.com/swampcooler/index.html. Eight watts for the fans, and the bird bath pump can’t be but a couple of watts. Easily done with a 100W panel, should be able to run overnight with a reasonable battery. That’s going to cool a room or a camper, though, and not a house.


That's helpful, thanks. I usually picture a squirrel cage fan with a big AC motor that has a big current draw at startup when I hear "swamp cooler".

I was under the impression swamp coolers needed big air flow to work well. Seems maybe not?


Isn't the humidity in the PNW way too high for swamp coolers to work?


High? I keep an accurate and calibrated hygrometer in the musical instrument room, and it's the rare day when it goes over 50% in Redmond. That said, I've never used one in the PNW.

According to the chart at the bottom of this article, it's not optimal, but it'll take the edge off: https://www.air-n-water.com/common-swamp-mistakes.htm. And for most summers, this one being an exception, our problems with heat are in the high desert east of the mountains.


Yes


Be careful and make sure you have redundancy, temps in campers can go way way up with a malfunction of the fan.


A solid point. Our mitigation is that it's a pop-up VW with a canvas tent and screen windows, and curtains on the glass windows. Even in the 90s parked in direct sun it'll stay cool enough to take a nap. It'll be a sweaty nap, but no one's going to die. And the design I linked to has four fans.

But now you've got me thinking about some WiFi or LTE module that monitors continuity or voltage, build a companion phone app that gets pinged when $SOMETHING goes wrong. :-) (Our use case is bluegrass festival->leave dogs in camper to see show, so we're never very far away.)


I would measure temperature directly, rather than continuity or voltage. It's what you really care about.

There exist smartphones with ambient temperature sensors; if you already have USB power, this is only a few hours of hacking.


I would measure temperature directly, rather than continuity or voltage. It's what you really care about.

Duh, of course. That's why they don't let me design things. :-) (Though in my defense, it was an "off the top of my head in 500ms" thought.) Plenty of power available, the only issue would be connectivity, as there's about a 50% chance that any festival we go to won't have a cell signal. Which makes me wonder how hard it would be to rig something that sends an APRS message over amateur radio frequencies when a the alarm has voltage, or something.

Anyhoo, this is drifting way off topic. If I get around to making something, I'll post a Show HN.


    big power hungry fan motor
Fans don't use much power. 50W would be fine for a swamp cooler for a tent. Are you thinking of on air conditioning compressor?


Here is a relatively tiny swamp cooler. It consumes 65 watts: https://thelashop.com/products/65w-portable-evaporative-air-...

I would have concerns with a 100 watt DC panel being able to handle a 65 watts AC swamp cooler. Conversion loss, motor startup current draw, etc.

Big alternating current fans that can move air do use lots of power. Especially a current surge at startup.

It sounds like in this space, people are making their own direct DC powered swamp coolers that are using less power, with relatively low flow fans. That's what I was missing.


This reminds me of a power box I built for Burning Man this year. The I had ~700W of solar panels, and in a box I put an MPPT charge controller, rather than the PWM charge controllers shown here, I had a 1kW inverter rather than 150W one shown here, but also tried to make most people in my camp use DC when possible, offering 2 USB plugs for each person in the camp, radio charging with a DC-to-DC converter, and a fuse box to prevent accidents. It worked out quite well, and we successfully ran a chest freezer and a number of other things off solar in the middle of the desert for a week.

Also, I used 2x100Ah deep cycle marine batteries + 2 additional batteries of unknown capacity, probably between 50 and 100Ah


Does battery type matter for the charge controller? Just learning about the differences between deep discharge lead acid versus lithium in another thread - can the charge controller optimize for battery life of either type?


In short, yes. In my experience MPPT and PWM generally are used in similar situations, the difference mainly being in how they charge and MPPT "making the most" of the available power (which is why they tend to be more expensive) and charge the same types of batteries.

Both charge batteries using pulses rather than a constant voltage which extends the lifetime of the batteries compared to a cheap automotive charger that would over time reduce the capacity of the battery), all of which is geared towards lead acid.

Most PWM or MPPT charge controllers I've seen only support lead acid (which come in a variety of configurations, some vented some not) and do not do li-ion, at least not out of the box. Theoretically they have the hardware to do it (my CC can do 12v, 24v, and 48v systems) but maybe not the software.

Lead acid batteries have been probably the most commonly used in renewable energy projects for a while due to their cost-density but li-ion seems like a superior choice if you can front the initial cost. I've been looking at them but also feeling like in 5-10 years there might be more alternatives so replacing lead acid batteries every 5-10 years seems better for me at this point.


Refreshingly practical site.

This is exactly why I think solar will beat nuclear hands-down. Solar enables gradual adoption, unlike nuclear's power-plant sized step function. Regardless of the actual price in $/kWh, people like doing easy things.


Solar is not practical in all places. I'm assuming you are talking about in general going to solar as a society, since I doubt many people are building their own nuclear batteries.


If you're going to be grid free you're going to need some kind of power storage.

So unless you can build a flywheel for $100 you're kind of stuck with batteries.


If nuclear is one of my options, I can probably afford more than $100 for a flywheel.


What is the problem with batteries?


This article and its predecessor made me think about smaller-scale solar, and I actually bought a 100W panel out of the Amazon gold box last week to start playing around myself.

My first plan is to use the panel and battery to run a set of 12V led outdoor lights, but I'm also thinking about trying to tie into the existing 12V system that I never bother turning on.

That's got me thinking about taking it a step further and adding some capacity to power my Christmas lights this year. Now that they're LEDs as well, it seems it should be possible, but probably not cost effective.

I keep thinking there must be a decent market in between tiny panels powering path lights and a full rooftop system. Like a standalone patio cover or pergola that has solar panels for a roof. That should give a decent amount of power, and it could be an easier sell to people instead of permanently attaching something to their roof.

Actually, I was trying to think of a way to run a small air conditioner from solar—like one of those split systems. The AC could run when the sun is out, which is when the upstairs of my house gets hot. It would be a supplement to my central AC, so I wouldn't be worried about it not running at night or cloudy days. So, I don't need a lot of storage or even worry about tying into the grid.

Again, though, it's probably not cost effective piecing it together, but still the solar patio cover seems like something that should available in a big box at Home Depot or Costco these days.


Wow, this is a great point – put a lot into perspective for me. This is exactly where I think there may be a gap in the market too – between path lights and rooftop solar. How to make a business around it without it being straight commoditized to Costco or Home Depot, though? Not that ending there would be a bad thing, but it makes it less of a viable business to build in the US...


And actually, a pergola/patio roof might be enough for a whole solar installation. I found a coffee stand with a metal frame solar roof and it made me think I should redo my patio roof as a solar system; I like the idea of not having to mount anything to my roof.

Plus, you can built it on the ground and then just tilt it up and bolt into place.


Some additional data (and comments) From the previous post about the system: https://news.ycombinator.com/item?id=14821478 here.


Looks like this is a new site.

The previous 'post' focused on apartments was discussed https://news.ycombinator.com/item?id=14821478


The kit consists of a 100W Pmax solar panel and a 420Wh [edited: this falsley said 420Ah before] deep cycle lead acid battery. The battery is pretty heavy and in the picture the setup is mounted on a car.

Let's keep in mind that a car alternator has 0.5-2kW and you need to burn <0.1l of gas to charge that battery once with the alternator. I'm not sure its worth all the extra equipment and cost to go full solar.

Edit: The solar panel probably gets you 360Wh to 900Wh per day, depending on how sunny the region you live in is. This is not enough to run a household refrigerator, but enough to charge your phones or laptops and some lights.


Optimizing for cost is not always the top priority.

For example, when you're camping or at another event with lots of people around. There's nothing quite as abominable as a fleet of autos chugging along in a loud cacophony.


> There's nothing quite as abominable as a fleet of autos chugging along in a loud cacophony.

If you have been to burning man you know there are things way more abominable.

That said, I agree cost is not the priority. Convenience is.


We have that battery in our camping gear for my wife's CPAP machine. It weighs 23 pounds. It's not hatefully heavy to deal with.

We started camping w/ a battery this summer and I'm definitely going to add solar charging. For me, the allure is to have the battery charging silently, and while we're away from the campsite.


Try this battery instead, if you want something lighter and more portable:

https://smile.amazon.com/gp/product/B01M3S00H0/ref=oh_aui_de...

I used it while camping for the eclipse, and only had to charge it once every few days, and that was with charging all sorts of other devices as well.


The "BOM" lists a 35 Ah / 12 V battery, which is reasonable. A 420 Ah battery is (a) a boutique item (b) should weight around 120-140 kg (c) does not fit into a toolbox (d) costs significantly more than 299 $.

From a professional standpoint I'd nag about

> the battery is laid into the tool tray. Plenty of extra space in this toolbox, which protects the system from dust and the sun.

A closed box is not a good place to keep actively cooled electronics; less so when it's a black box in the sun.


You can get passively cooled 150W inverters, but yeah, a black box outside in the desert may not be ideal. You can eliminate most of the radiant and some of the convective heating with a beach towel on the box and an umbrella+emergency blanket above it. (I mean, we are talking burning man, after all)

If you seal your box in a humid environment, the cool night temps can cause condensation, so ventilation of the box would be useful to prevent this (as well as provide for active or passive cooling of electronics) or throw in some silica gel packs.


The box is mostly to prevent dust ingress which is arguably a bigger problem than heat or condensation on the playa.


Thats not true.

If you suppose a 12V 420Ah battery, its capacity will be of 5kWh. That would require at least 0.5l of fuel. But with a typical efficiency of 30%, it will require 1.6l, and not 0.1l.


My mistake, I meant 420Wh. Thanks.


This is a teeny setup, but it is also easy to scale up. This setup gives you everything you need to get started and you can add or replace parts to get more capacity and current. With the project box and a folding shopping cart you could haul two larger batteries and several panels.

If you have money, you can buy integrated solutions like the Xantrex XPower Powerpack 1500 + regulator + solar panels.


I have a "plan" (we'll see where it goes when I get to it) to do something like this on my Jeep for camping. Except, instead of an external battery, my plan is to get either an Optima or Odyssey hybrid battery (maybe two, if I can fit them under the hood), that can be used for cranking and deep-cycling.


So for $200 you can keep your devices churning while not connected to grid? That sounds pretty nice if you like longer road trips and mainly visit places with a lot of Sun light.


I think that's the main goal (charging phone+tablet+laptop). He's talking about that in one of the other posts on the site.


I have a desire to use something like this for a mining rig with 4 nvidia 1070 cards, but have conflicted info in what need.

According to https://www.nvidia.com/en-us/geforce/products/10series/gefor..., the cards pull 150w. But how to know what setup work?

BTW: I live in Medellin, Colombia and have sun like half-day for sure.


Energy is interchangeable. You don't need to attach the solar power to the mining rig.

Just use solar power for whatever, and grid power for the mining rid and it works out the same.


Ok, but how calculate what I need (ie: How many solar panels, battery, etc)?


This is described as "green" but as a portable the panel will never produce as much energy as it took to manufacture it. Taking this deficit into account plus the energy and other environmental harm embodied in the battery, which will also likely be sparsely used, and its doubtful you beat diesel by much.

To truly be green you would either do without or not go.


I've always wondered about this logic... Seems like the greenest thing a human could do would be to decompose underground.


That's probably true, if you don't want to count your influence on the carbon footprints of other people when calculating your "greenness". You should probably count it though.

So then, the very greenest things you can do probably involve mass murder and industrial sabotage.

Further down the list, after those, you have leading an ascetic life of minimal consumption and minimal travel while devoting yourself to the right sort of political advocacy.

A bit further down is dying underground as soon as possible. But it's important to note that a small amount of advocacy, sabotage, or murder per year can make it a net positive for you to continue living.

Way below all that stuff that nobody wants to do (and who can blame them) are (a) living as a hermit in the woods eating only berries and mushrooms or (b) living a normal life with a normal career and making consumer choices like buying solar panels and electric cars when other people might buy various combustion machines.

If you're not counting your effect on other people, (a) is a clear winner. However, people's consumer choices do have an effect on the direction of the economy. And, if you take those effects into account, I honestly don't know how to decide whether (a) or (b) appears higher in the greenness ranking.


I commented because of the claim from the article that this "personal power plant" was green. The people that read that shouldn't be misinformed, it could cause them to make choices that are counterproductive if being (relatively) green is their goal.


I am skeptical of this claim.

Maybe standard rooftop solar panels lifetime is too short as they are exposed to the elements all the time. But as a general rule? Seems wrong.

Solar panels will generate power for as long as there are cells still alive.

Both are recyclable, but batteries are specially so. Therefore, how can't they beat diesel, which also has to be extracted, processed, transported and finally burned (at low efficiency)?


Portable panels will only be used a tiny fraction of the time that a dedicated roof install will be.


The embodied calculations are here, but they are based off an optimal scenario – http://gridlesskits.com/2017/02/12/Financial-Payback.html


I looked at this more closely, you linked to a portable Burning Man scenario. Using this in an apartment as you describe (especially for 4+ years) is a significant hazard. Alligator clips and no enclosure? Non-outdoor rated cable running free down the structure through a window? Panel with no mounting sitting on the roof?

Show this to a landlord and see what their reaction is.


This is if the setup is producing power 365 days a year for 4+ years. Its extremely unlikely these systems will be used in that fashion.


Especially if one is flying there. Just not flying there would be a huge exchange in carbon footprint.


Just drop dead to minimise your carbon footprint the proper way


Are you dismissing as absurd the notion that a person might want to alter their lifestyle in order to reduce their carbon footprint?


Is it safe? Is the battery protected against going under or over capacity?


They include a solar controller + battery regulator in the parts list.


I don't think the solar controller or the inverter has undervoltage protection.


Not nearly as turnkey, but for a little extra fun you can also build your own battery bank from reclaimed laptop batteries. Search youtube for 18650 battery bank.


Actually, if you want a (relatively) cheap battery bank for solar, find a place to sell you used golf cart batteries. They are typically 6 volt, but are deep cycle (big and heavy). Wired up properly, they can work really well, and cost a fraction of what new batteries would.


How many months / years would it take for this to generate $200 worth of electricity at some normal price for electricity in the US?


It generates about 1kw per day. Worth say $0.15. So about 4 years, if you never have clouds.

In the real world I'd probably double that to 8 years.


Oh.. so I guess it wouldn't be worth it unless you are away from the grid.


Keep in mind part of the cost is the battery, and you would not need that if you are grid connected.

On the other hand the inverter would be more expensive, since you can't just use any old cheap inverter, but you need one that is true sine wave (cheap ones are filtered square wave), and able to phase and voltage match to the grid.


People said this on the previous DIY solar thread, but I wasn't sure where to exactly look for one. Could you link me to one that is a true sine wave?

And how would I verify that this works for my electricity provider (PG&E in San Francisco)?


Sorry, I don't have any product suggestions. Google for "Grid-tie inverter".

And don't forget true sine wave is not enough, it must also voltage, and even more important, phase, match.

You don't need anything specific to any particular electricity provider.


As soon as you get into batteries, aren't you still treading into non-eco friendly waters? I suppose this is more about self-sufficiency, but you're still relying on rare metals that come from questionable sources and are excavated by the same old diesel power.


Is the alternative no batteries at all for no power at night/overcast days or is lead-acid OK over lithium or not?


Most batteries are made to be recycled. Only a fool throws rechargeable batteries in the trash (not to mention such batteries being bad for the environment disposed of in such a manner).

There are plenty of places to recycle both lithium-chemistry and lead-acid batteries (plus any mercury containing hearing-aid and similar cells). For car batteries, you can usually trade in the old battery for the "core charge", otherwise there are places that purchase old lead acid car batteries and similar.

Virtually everything in those batteries is recycled, and usually turned into new batteries again (heck, I think they ever recycle the sulphuric acid, too).


.. I'm guessing I'm not the only one who would be quite happy if someone would do a smaller, lighter, cheaper version of this:

http://smartflowersolar.com

Perhaps DIY is the way to go.


This would be a really great small-generator alternative for hurricane zones


Not much sun in the middle of a hurricane.


There is afterwards when you don't have power for two weeks. I sure could have used anything after Wilma in 2005 to beat the heat.


To save people some time:

Solar panel can push 100W in. Invertor can pull 150W out.


Can you elaborate? I'd love to get 150 joules out of a system I only put 100 joules in to...


Time is a factor. You have to charge for 1.5 hours to be able to pull in 1 hour (minus system losses)


A Watt is an SI unit defined as 1 joule/second, and is used for measure rate of energy usage/generation. So this system generates up to 100 joules/second, and can output up to 150 joules/second (until the stored energy is consumed).


That's the max charge and discharge rates. The battery capacity is a separate number. You can only discharge what you have in the battery.


The inverter can pull 150W out. That doesn't mean it does. His main load is a swamp cooler, which doesn't even seem to be using the inverter.


Why do the green straps appear to be going directly over the panel? Surely that is not the final mount position?


The winds in the dust storms were mad strong – I think Sean battened it down with the straps for safety. I still regret not getting a photo when he initially had the panel tipped forwards towards the camera (worse for generation, better for photos...).


What if I source the parts from AliExpress instead of Amazon? Should be quite a bit cheaper, right?


Possibly not UL approved though.


I'd recommend adding fuses. One between the panel and charge controller, and one on V+ to the battery.


I would say it is an absolute necessity. Charge controllers have a tendency to fail resulting in a dead short (connecting + to - on the battery, resulting in a fire, explosion or something in between).

I had this happen on a properly wired off-grid system (bad diode) and it would have been quite bad had it not had a breaker of the appropriate size. I would not sleep next to a battery that wasn't fused or breakered.

Reminder: DC systems and AC systems require differently rated components. You cannot just go buy a 30A breaker from home depot for the DC side of your system. It takes a lot more to disconnect DC than it does in AC (because AC cycles to 0V 60x/s it doesn't take much of a gap/insulator to break a connection, DC is not the same. Trying to use a light-switch for a DC light can result in problems [1].

I've had good luck with midnite products (charge controllers and breakers, etc) [2]

[1] http://blog.gogreensolar.com/2015/02/ac-vs-dc-breakers.html

[2] http://www.midnitesolar.com/products.php?menuItem=products&p...


Pretty neat, but how do you get ice to burning man for the swamp cooler?


Ice is one of the two things they sell at Burning Man.

(Officially. In reality there are a few more things that they sell, but the 'only two things' label has stuck).

Edit: Also, you don't need Ice for a swamp cooler. You don't even need cold water. The water temperature doesn't really matter, as the temperature drop comes from the evaporation, not the water temperature.


Why not use a ups for the battery?


Can't efficiently charge from solar, so you need an external charger anyways. Not really cheaper than an inverter. Cheaper ones are not intended to run continuously and may overheat.


Also, most will beep annoyingly once the sun goes down.




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