
Tesla’s promises don’t compute with current physics and economics of batteries - watchdogtimer
https://www.bloomberg.com/news/articles/2017-11-24/tesla-s-newest-promises-break-the-laws-of-batteries
======
nimos
The Tesla superchargers currently charge at around 2% a minute up until about
80% which is 40 minutes to hit 80%. Tesla is advertising 400 miles in 30
minutes which is 80% of the 500 mile capacity. What is so hard to believe
about a 33% improvement over a couple year old tech that is a couple years
from release?

Here are current industrial/transportation/residential electric prices in US
[0]. They think Tesla will pay 40c a kwh??? What a joke. Sure if you look at
constant demand facilities and extrapolate their pricing model with low
average demand to megachargers you can come up with a ridiculous number. You
can literally run diesel generators and generate electricity for a lower cost.
This is so hysterically asinine I can't believe Bloomberg published this
article. Not to mention a huge amount of charging can happen overnight when
drivers are sleeping and electricity prices/demand are super low.

Pushing a lot of power through a wire is a solved problem. So what they need
to push 10x through one connection instead of over 10. We are talking about a
modest increase in % charge rates. That is what matters. All else equal you
can charge a percent of your battery capacity not some arbitrary fixed number.

This is an embarrassingly poor article. I think the one the worst things about
the current tech shortage is now we have all these arts/business majors doing
technology writing larping like they know the difference between a watt and an
amp.

[0][https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...](https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a)

~~~
jepler
Look at charging rates in watts (watt hours per hour) instead of in
percentage; those semis have much larger capacity batteries, so they need a
higher charging rate in W to charge 80% in 30 minutes than a vehicle with a
smaller battery.

~~~
cperciva
They don't have _larger capacity batteries_. They have _batteries with more
cells_. Sure, the total charging rate is a higher Wattage, but you can charge
cells in parallel.

The scaling here is exactly the same as with the "larger battery" versions of
the Model S having more horsepower; higher capacity = higher throughput when
you're dealing with battery banks.

~~~
kumarvvr
Wait, are you concluding that having batteries with more cells is not the same
as increasing the capacity of the system?

For any battery system, the capacity is the product of the number of cells and
capacity per cell.

~~~
cperciva
My point is that having a larger capacity battery automatically increases the
wattage at which you can recharge. It's not like a gas tank where a 100L tank
takes longer to refill than a 50L tank.

~~~
kumarvvr
No, capacity of the battery isn't what determines the wattage at which you can
recharge. It's the physical power supply constraints.

If I have a 250v, 25 kWh battery, I can charge it at 250 V, 100 Amps for 1
hour or at 250V, 1000 Amps for 6 minutes.

What charging rate I select depends on the voltage and chemistry in the
battery. Can the battery support charging at such a rate. The charging current
rate is limited to the max operating current of the battery.

If the above battery can supply a max current of say 50 amps, then you will
have a max charge rate of 250V, 50 Amps for 2 hours.

~~~
petre
What makes it confusing is that the charging rates are given as 10C, meaning
10% of nameplate capacity.

~~~
jsjohnst
That’s wrong. 10C means 10x the nameplate capacity. If I have a battery that
outputs 40Ah, 10C means I can give it a charging current of 400A.

------
ams6110
If this were any other company making such unsubstantiated claims that didn't
have any basis in the reality of the underlying technology, they'd be getting
roasted here.

~~~
jsight
I don't really agree. If another company rolled a 200kwh car out of the back
of a truck, did a few passes of the stage, gave passengers rides (high speed
launches) for a while, and then reported ~60% battery remaining, I think most
would believe them.

We would also wonder about making it to production, but Tesla actually has a
halfway decent track record at that.

~~~
lukealization
> If another company rolled a 200kwh car out of the back of a truck ...

That's the thing. They didn't. The roadster concept didn't have 200kWh in it
at all.

~~~
_ph_
It might not have exactly 200kWh of battery installed, but one reason for
planning such a large battery is to be able to support the neccessary current
levels for the accelleration they have demonstrated. So they couldn't have
just put a small battery in the car either.

------
techbubble
What would prevent the battery from having a segmented design so that multiple
segments can be charged in parallel? Is there something about the chemistry
that requires the entire vehicle battery to be a single unit?

~~~
TylerE
At some point the size of the connector TO the vehicle is going to be the
limiting factor.

~~~
andreyf
In the case of a truck, that seems less likely -- surely they could come up
with a design that hooks in 2, 3, 10 plugs the moment the truck is ready to
dock.

~~~
simonsarris
Their design has 4/8 ports: [https://insideevs.com/wp-
content/uploads/2017/12/Tesla-Semi-...](https://insideevs.com/wp-
content/uploads/2017/12/Tesla-Semi-Charging-Port-2.jpg)

~~~
andreyf
Nice! I guess the width of the wires is the limiting factor? Or a cooling
system? Regardless, curious to hear an informed analysis.

------
mcguire
" _Tesla offers free electricity to most of its Model S and Model X customers
while paying almost $1 per kilowatt hour to produce it, Morsy said. That
amounts to a subsidy of as much as $1,000 per car in 2017._ "

I realize that most people believe that Tesla and Uber will be able to
continue subsidising their operations indefinitely, but it makes me very
nervous.

~~~
jsight
I can't take this author seriously. There is no way that Tesla is paying
$1/kw. That is way past the retail rate, and I bet that they are paying much
less than the retail rate in many of their markets.

~~~
bryanlarsen
They would if they were pulling straight from the grid. Go to your power
company and ask how much it would cost to surge a mega watt of power at peak
times. Those kinds of surges are really expensive to handle. Of course Tesla
uses storage and solar to smooth their demand so that they can pay normal
rates.

~~~
nimos
$1/kwh is a joke price. Peaking natural gas plants run at 20 cents/kwh on the
high end. You can go buy a honda gas generator from home depot and run it for
1-2k hours and pay less than that per kwh.

------
ChuckMcM
Given Tesla's recent experience in building the South Australian battery bank,
I wonder if it is possible to build something similar at a truck stop.

Imagine a 10MWh battery pack that constantly charges from the grid, when a
truck pulls in it can dump charge into the truck at a high rate.

I was thinking about diesel which is trucked in to the truckstop and stored in
tanks, and then pumped out when needed. This would store charge in batteries
and then pump it out when needed.

------
watchdogtimer
> To meet Tesla’s claim of 400 miles in 30 minutes for a semi carrying 80,000
> pounds would require its new Megachargers to achieve output of more than
> 1200 kW

1200 kw is a lot of power. That's the average amount of power used by 600
homes, or half of the output of a large wind turbine here in the Midwest, to
charge a single truck.

If they use a 440 V supply to charge it, that'd be over 2700 amps.

~~~
dboreham
I might have been skeptical too but I recently saw a _ship_ charged while
docked for about 50min in Norway. Big plugs, two circuits and I think 600V. I
took a picture that I could dig out for the curious.

~~~
blhack
Wow I would love to see that!

Am I reading this right? A _electric_ ship?

~~~
gamblor956
No, a normal ship. To minimize pollution, most ports now require cargo ships
to run their electrical systems off of harbor power while docked (instead of
using the ship's own diesel generators).

------
itchyjunk
Although it is very good to be skeptical, it makes the article less valuable
than it could have been. 'Musk claimed X and people we talked to said they
don't know how it's possible.' I am not saying that the people they consulted
didn't know how, but using just that for the entire article was unnecessary.
They also claim battery density is increasing by Y% and maybe Tesla is banking
on that. Well those density increases because someone somewhere is finding
ways to do it. It's not happening by some magic. Maybe Tesla found some ways
to improve it? Why do they have to rely on someone else?

Maybe I am being too critical of the article and I understand that author too
can do very little but speculate. But maybe consult variety of people rather
than just 'I don't know how so it must not be possible' people.

Edit: is there a way for tesla to purchase electricity for solar city
customers or something and direct it to charging stations? Or is that now how
it all works?

~~~
shobith
They could have easily added a few more people speaking while they were at it:
[https://asia.nikkei.com/Tech-Science/Tech/New-battery-
techno...](https://asia.nikkei.com/Tech-Science/Tech/New-battery-technologies-
still-years-away?page=2)

~~~
itchyjunk
Very good supplement information. I didn't realize Li ion batteries were so
close to their theoretical limit.

------
xg15
> _Musk’s claim that the truck will be able to accumulate 400 miles of charge
> in 30 minutes would allow the Semi to achieve the first true long-haul
> ranges in the industry. A driver might start the day with 500 miles of
> range, top off the battery at lunch, and be able to complete driving the
> U.S. legal limit of 11 hours in a day with range to spare. But doing so
> would require a charger unlike anything seen before._

Stupid question: Why is it no option to simply hot-swap the battery? (Possibly
with mechanical assistance)

If you're already talking about a scenario where the charging happens at
motels or gas stations, it seems easiest to have a stock of batteries that you
can charge over longer time and swap them out whever a truck comes in.

~~~
lovemenot
This is more of an economic / business problem than a technical one.

Just who do you think would be the owner of the replacement battery packs?

If your answer is Tesla, then you've made huge and IMHO unrealistic
assumptions about Tesla's capital allocations.

If you expect haulage companies to buy and charge batteries around their most
likely needed locations then you are even further off. In nearly every case,
their business demands extreme routing flexibility.

------
johngrefe
It breaks the "laws of batteries" until it doesn't. Has everyone lost their
memory retention? Maybe everyone on HN is Software centric and hardware
hobbyist. Fair enough. Big things coming in the battery space.
[https://news.utexas.edu/2017/02/28/goodenough-introduces-
new...](https://news.utexas.edu/2017/02/28/goodenough-introduces-new-battery-
technology)

------
pfarnsworth
Can't you just have multiple super-chargers charging different banks of
batteries in parallel?

~~~
fencepost
Not sure why this is getting downvotes, it seems like a blindingly obvious
part of the system. As for power to the chargers and paying high premiums for
surge loads, it's a real shame there's no technology that Tesla could use to
accumulate and store power locally at stations with local storage capacity
determined based on expected usage.

For that matter, just take the flat frame/battery pack of the current cars and
make them replaceable slabs on rails. Charge each one independently or swap
them out, though that'd probably be a service thing instead since you probably
want to keep those trucks on the road as much as possible.

------
mgiannopoulos
Bloomberg trying to manipulate the stock price? Could it be?

------
mirimir
It's an informative article, but the title is inaccurate. Tesla seems to be
relying on plausible extrapolations for batteries in ~2020.

~~~
mtgx
Bingo. Not only that, but they may even rely on battery extrapolations for
2022, despite the truck and car being launched in 2019-2020. All they need is
to break-even in the first year or two, and then they can make-up the profits
from the improvement in battery prices. That said, the roadster itself will
likely be profitable from day one. It's the truck that may not be.

This is why Musk keeps getting ahead of everyone else and leaves carmakers and
media writers in "shock and awe" \- because he keeps thinking outside of the
box, while they keep thinking within the _existing_ or _past_ constraints.

~~~
flor1s
Meh, I think other companies just don't have the bravoure a man like Musk has.
Also it helps if your company is a start-up and no heads will roll if you
don't make a profit. Established companies don't have that luxury.

~~~
toomuchtodo
Established companies keep their stock price high by being conservative.
Startups/growth companies keep their stock price high by pushing the envelope.

------
joshuamcneese
The “laws of batteries”?

~~~
melling
“Every time the global supply of batteries doubled, prices drop 19%”

“Every year the energy density of batteries increases by about 7.5%”

So, in 10 years electric cars will double their range, which should be more
than enough for most people.

~~~
Hypx
We should be careful with apply Moore's Law style of thinking when it comes to
battery innovation. These things can and will hit hard limits at some point.
Real progress can be much slower and much less predictable than in the
semiconductor industry.

~~~
jsight
The funny thing is that it really hasn't been that much less predictable.
Progress has been slow but steady and Tesla's business model has been built
around largely predictable technological progress.

7.5%/year is probably an overestimate, though, and you are right that at some
point it will hit diminishing returns. Moore's law has too, though, eh?

------
marklyon
The correct term is “disrupt”.

------
MentallyRetired
> based on Bloomberg's estimates

Oh, good. I thought they were going to bring in a battery expert to disprove
the battery experts that work for the company who, according to Bloomberg, has
the most advanced charging systems on the market. Whew! Dodged a bullet,
there.

------
excalibur
I think most people are in agreement that the lithium ion battery is less-
than-ideal technology that's due for replacement. And we have a number of
innovations in battery technology vying for the opportunity.

It's starting to feel a bit like Tesla's massive investments are only serving
to further entrench the existing battery model. He's basically working to
replace Big Oil with Big Lithium. There's no denying the benefits of breaking
our addiction to fossil fuels, but we need to be mindful of the obstacles to
tomorrow's progress we're erecting in the name of today's.

~~~
dreamcompiler
> He's basically working to replace Big Oil with Big Lithium.

Electric cars need X kg of elemental lithium over the lifetime of the car. ICE
cars need [on the order of] X kg of gasoline every 200 miles. This makes such
a huge quantitative difference that comparing lithium mining to oil mining is
almost pointless.

In addition, lithium can in principle be recycled when the battery wears out.
Gasoline cannot be recycled, even in principle.

~~~
nbanks
Some CO2 hydrogenation processes can produce liquid fuels which is kind of
like recycling gasoline, but this is much more complicated than recycling
batteries. It may still prove useful for fueling rockets or aircraft in a CO2
neutral way.

~~~
dreamcompiler
Understood. My former employer was researching this. But taking the separated
atoms of gasoline and rebuilding hydrocarbon molecules from them is -- as you
say -- not quite the same thing as recycling. And it requires very large
energy inputs. It only really makes sense for aircraft fuel, since large or
high-performance aircraft cannot (yet) be powered by batteries.

