
Inside the Tesla 100kWh Battery Pack - tjomk
http://skie.net/skynet/projects/tesla/view_post/20_Pics+and+Info%3A+Inside+the+Tesla+100kWh+Battery+Pack
======
ZeroGravitas
I wonder if anyone has estimated the impact of "simple" engineering changes on
the progress of electric cars.

I have seen things that extrapolate out battery progress, so if batteries
become cheaper/lighter/more powerful in a similar way they have in the past
then that has a big impact on EVs, dropping their price and/or increasing
their range.

But a lot of things seem fairly simple, if not obvious except with hindsight
e.g. heated steering wheels and seats instead of air heating, heat pumps
rather than resistive heating, puncture resistant tyres rather than carry a
spare, led lighting, replacing side mirrors with cameras for lower drag etc.
How much can straightforward, no new tech, improvements in all these areas
actually help if you add them up?

~~~
Hermel
> e.g. heated steering wheels and seats instead of air heating

The next step could be microwave heating systems that directly heat your body.
But I would probably not feel comfortable with that.

[https://www.wired.com/2008/01/pain-beam-
centr/](https://www.wired.com/2008/01/pain-beam-centr/)

~~~
espadrine
Let me see, people are already really upset by cellphone radiations, which are
non-ionizing and therefore can only be harmful from the heat it generates.

You would need marketing masterminds to sell this.

~~~
delecti
All it would take is one mommy blogger to make the connection that cell phone
signals are _already_ microwaves.

------
Fifer82
Is it really just an array of 18650s? Seems primitive??

~~~
owenversteeg
18650s are pretty much the only way to get decent energy densities and allow
for high power output. What a lot of people don't know - which I find
fascinating - is that discharge rates on batteries are set mostly by how much
heat the battery can dissipate safely, and not as much by the cell chemistry
itself. Looking at a random 18650, it may be able to (in theory) put out 200
watts, but the cell would be permanently damaged by the intense heat produced.

As a result, if you build an enormous single cell battery, even though it
seems futuristic, it'll be horrible at distributing heat. A Tesla pack that
was consolidated into one cell would basically be an enormous furnace at any
reasonable discharge rate, and they'd have to discharge it at a very low rate
in order to prevent it from permanent damage and/or fire.

If there's one thing to call "primitive", it would be the new low cost 21700
battery cells Tesla is producing; these have shockingly low power and energy
densities, and disappointing cycle limits. They are cheap though, and that
seems to be why Tesla's making them: for lower cost vehicles.

~~~
justin66
> If there's one thing to call "primitive", it would be the new low cost 21700
> battery cells Tesla is producing; these have shockingly low power and energy
> densities, and disappointing cycle limits. They are cheap though, and that's
> why Tesla's making them: for lower cost vehicles.

Two claims here - that the batteries have lower energy density, and that
they're intended only for lower cost vehicles - go against the common
narrative among Tesla people. Can you provide any background on this?

~~~
owenversteeg
TL;DR 21700s produce less power (not necessarily energy) for the same cycle
length and weight, so Tesla will either have to reduce power consumption of
their high end vehicles -or- add more batteries, which adds weight. Both of
these things reduce performance.

I'll be honest: I've got much more knowledge about batteries than I do about
Tesla's strategic direction.

I do know that there are currently problems with Teslas sustaining their power
output when on high performance mode. Since the power density of 21700 cells
will almost certainly be less than 18650 cells (this is basic physics) [0] I
think they will use 18650s for their performance vehicles. However, I could be
wrong; they -could- simply increase the number of cells used and make the
vehicle heavier. Strategically, I would use 18650s (at least with the
performance cars) if I was Tesla. However, for PR reasons they may choose to
use 21700s and compromise the performance of the performance cars.

My claim that they have a low energy density is on less strong ground, of
course. As Musk said during the Q3 2014 conference call, "show me the cell,
not the powerpoint." I only have powerpoints and no cells. However, the
powerpoints I do have show that the energy density will be between 220 and 260
Wh/kg. They may be up to 280 Wh/kg. But I doubt that they'll beat the current
maximum of 310 Wh/kg that you can get today.

Tesla does a lot of really cool stuff, but there's a bit of a Tesla reality
distortion field going on. For example, this post here [1]. Some genius
speculates that batteries grow at a 5.94% compound rate, and then extrapolates
to assume that Tesla's cells will reach 350 Wh/kg. Here's the kicker: li-ion
battery cell capacity has been practically stagnant for 11 years. In some of
these 11 years, the cells have gotten cheaper, but not by much. If we truly
had grown at that 5.94% compound rate for the past 11 years, we'd currently
have a 528 Wh/kg cell today.

Li-ion battery energy density grows in spurts. Realistically, there have been
a few major improvements, with very small incremental improvements in between.
For example, in 2001 we were at 180 Wh/kg. In just a handful of months we
jumped to 260 Wh/kg, then to 280 Wh/kg as manufacturing processes improved. In
the last 11 years, however, improvements have been maybe a few Wh/kg per year,
and there have been literally zero improvement whatsoever in the past four
years, by anyone.

I think Tesla - may - get a bit north of the 310 Wh/kg we can get today, and
I'm confident in their ability to reduce costs, but I don't expect anything
revolutionary (energy density wise) like Musk implies in his presentations.
I'd set the threshold of 'revolutionary' at 400 Wh/kg, a 29% improvement from
today.

For future-me-check-if-I-was-right purposes: these estimates are for Tesla's
cells released in early 2017.

[0] The larger a cell is, the lower its theoretical power density must be.
Power density is a function of power dissipation, and larger cells are worse
at dissipating power. These new cells are only a few millimeters wider, but
that's enough to increase their volume by 50%, which means their power density
will almost certainly suffer.

[1] [https://teslamotorsclub.com/tmc/threads/21-70-cell-
informati...](https://teslamotorsclub.com/tmc/threads/21-70-cell-
information.74652/#post-1683564)

~~~
cesarb
Are you comparing the Tesla 21700s with all the commercially available 18650s,
or with the specific 18650s Tesla uses? It's possible Tesla doesn't use the
most energy dense 18650s available, so their 21700s could be an improvement
for them.

Also, are they currently limited by the heat dissipation? If not, increasing
the volume per cell might not be as much of a problem. The linked article
mentions that they doubled the number of cooling loops per module, which might
already be anticipating an increase in heat to be removed.

~~~
owenversteeg
> Are you comparing the Tesla 21700s with all the commercially available
> 18650s, or with the specific 18650s Tesla uses? It's possible Tesla doesn't
> use the most energy dense 18650s available, so their 21700s could be an
> improvement for them.

For reference, Tesla's current cells are about 215 to 225 Wh/kg; they are not
the most energy dense cells you can get. What I'm comparing are Tesla's new
cells to the best cells out there. The reason why I do this is because that's
what Tesla fans - and Elon Musk - repeatedly do. Also, I'm almost certain that
Tesla's new cells will have a higher energy density than 215-225 Wh/kg; if
they didn't, they'd be on par with batteries from a decade and a half ago,
which would be pretty pathetic.

> Also, are they currently limited by the heat dissipation? If not, increasing
> the volume per cell might not be as much of a problem. The linked article
> mentions that they doubled the number of cooling loops per module, which
> might already be anticipating an increase in heat to be removed.

It's complicated. Technically, at the rate of discharge that Tesla uses right
now, they shouldn't be. Teslas right now discharge their 65-100kWh pack in 3.5
to 5 hours. That's about 20 kW power continuous. There are roughly 6000 to
9000 cells per pack, so very roughly you discharge, while driving, between 2
and 3.5 watts per cell, so around 0.2C discharge. However, Teslas have their
packs in an enormous, insulated, heavily managed sealed blob of batteries.
This confines the heat to the pack, which requires their water cooling system.

Another complicating factor is that heat dissipation matters in a few
different contexts. First, there's the important matter of getting the heat
from the inside of the battery to the battery surface; this is a matter of
battery design and solved by the people that make the batteries. Then, there's
the matter of what you do with the heat once it's at the battery surface
(Tesla water-cools their cells); this is a problem for whoever makes the
battery pack. Then there's the problem of what to do with the heat in general;
now that you've drawn the heat away from the batteries and into the heatsinks
or water, how do you cool your hot water/hot heatsinks?

Switching to 21700s 'only' changes the first part of the equation - heat
dissipation within the cell - but this is one of the trickiest parts to deal
with. You can put a water cooling system on the outside of your battery, but
you can't put a water cooler in individual cells. You can change the chemistry
of the battery to better dissipate heat, but changing the chemistry of course
also changes the battery's characteristics: energy/power density, cycle life,
weight, cost, etc.

------
dzhiurgis
If you managed to find ~50kg motors & wheels and strap them directly to this
battery pack, you could do 0-60 in 1 second.

~~~
hunterwerlla
I know this is a joke but you really couldn't, traction (friction) plays a
huge role in 0-60 times and something so light would not have that much
traction.

------
Shivetya
[https://teslamotorsclub.com/tmc/threads/my-take-on-the-
new-1...](https://teslamotorsclub.com/tmc/threads/my-take-on-the-new-100kwh-
pack.76065/)

The above has some better details but the one I cannot find is weight of the
pack, assumptions put it near 1300lbs. Weight is the one area batteries suffer
compared to other alternatives and it needs to be addressed because weight is
one area car makers are trying real hard to solve.

------
yazinsai
Does anyone know how they get around faulty individual cells taking out the
whole group?

~~~
cesarb
Fuses and active cooling.

Each module has six groups connected in series, and each group has dozens of
cells connected in parallel, each cell with its own tiny fuse (see the
pictures in the article). If one cell shorts, the fuse removes it from the
group, while the rest of the cells in the group is enough to keep it working.
And the active cooling removes the heat released from a failing cell, so it
won't overheat its neighbors.

------
ethagknight
Can anyone explain (or hazard a guess) why Tesla uses cylindrical cells verses
the 'scalloped potatoes' approach of Apple's newer laptops?

~~~
lykron
Cheaper to buy standardized cells at scale, due to production capacity?

~~~
lsaferite
With the giga-factory coming online I wonder if that will change the equation
in favor of flat cells instead.

------
seesomesense
tldr: "Basically they crammed a couple more rows of cells into the module."

~~~
DiabloD3
Between that and the ever so sliiightly higher capacity cells they already
adopted, I can't see them getting any more performance out of the existing
tech.

That, and 100kwh for a Model S battery is pretty damned good, could probably
set a 650+ mile record under special handling (current record is 550 miles on
a 85D).

~~~
TomMarius
I don't want to specially handle my car every day. The car is good for in-city
usage, but if you're travelling a lot and live in Europe, it's still long from
being usable.

EDIT: an explanation of the downvotes would be nice.

~~~
hueving
I'm not sure why you are getting downvoted so bad. It's a fair point to bring
up when people bring up these 500+ mile range runs. The Tesla is restricted to
being an amazing city car, and that's OK.

Even if you're in the US and you live in a remote location, the car is crap
for road trips. For example, you live in Rock Springs, WY and want to drive to
Buffalo, WY. You will be lucky to make it on one charge and adding a
supercharger to the route will take you hours out of the way.

~~~
lorenzhs
Y'all pretend like there's nothing between a city car and a car that regularly
does 500+ mile trips. EV's aren't at the point where really long trips are as
convenient as in a combustion car, that's not news. But the range that they're
good for has been steadily increasing, and so have the goalposts of the "I'll
buy one when they can do XYZ miles on a single charge" comments.

This discussion has been had so many times, I can't blame people for
downvoting it. Nothing new is going to come of having it again, it's just
going to derail the thread.

~~~
hueving
But the comment was in response to a comment about a 550 mile record. I think
that brings fair game to point out that nobody can reliably use the thing to
perform trips 85% that long frequently. For example, someone who classifies as
a "mega-commuter"[1] would not be able to use a Tesla unless their office has
a charging station.

1\. "Across the United States, mega-commuters on average spend two hours to
traverse 166 miles just for the lighter morning commute "
[http://www.mercurynews.com/2013/03/04/bay-area-tops-new-
mega...](http://www.mercurynews.com/2013/03/04/bay-area-tops-new-mega-
commuter-census-list-defining-the-worst-trips-to-work/)

~~~
icebraining
_For example, someone who classifies as a "mega-commuter" would not be able to
use a Tesla unless their office has a charging station._

Pedantically, some would, since to be a mega-commuter you only need to travel
50 miles in each direction. Average != all.

------
ge96
I wonder if there is any potential danger to having a public Bitcoin wallet
string. I don't know if you can "receive bad money" for example. I don't know.

~~~
EdHominem
Yes and no.

"Coins" aren't a thing, so there's nothing to be tainted, per-se. However, yes
- if an address that ordered a murder sends you a lot of btc, expect someone
to come by and discuss it.

Also, the waters are muddied now (intentionally), in a similar way to how
every piece of American cash is rumored to have traces of cocaine on it. The
theory is that the more this implicates everyone, the less it implicates
anyone.

~~~
ge96
I briefly searched on it, the one thing they mentioned was the possibility of
being able to link exchanges to other unknown people because you're now known
if your website says who you are and you have a key right there. But they also
said to use other ones for each transaction. I don't know. Anyway thanks for
the info. Bitcoin is a bit volatile for me but I appreciate it's capability
and would like to have some in the future. I'm also broke/in a lot of debt so
any concept of savings... Anyway I'm trying to "spread out my money" so to
speak for a safety net. I don't know.

~~~
EdHominem
If you're in debt, you need to pay off your highest-interest creditor first,
and then on to the next one. When you have spare money, you can hedge bets on
investing it.

But, Bitcoin is _not_ an investment.

First, nothing _you_ don't understand is ever an investment for you. If you
don't know mining and I do, I'm investing by buying shares in a mine whereas
you're gambling by doing it. (For instance, if you don't know, and really
understand, why bitcoin tends to be used in a manner where you empty the
balance from one address, sending some to the intended recipient, and the
leftovers to yourself at a new address, then you're not ready to invest.)

Second, it functions as a store of wealth not capital. Its gains are partly
from other currencies devaluing around it, not it being used to create more
goods the way buying a piece of capital (shares in a manufacturing company)
would.

That said, if you do any gambling (lottery tickets) you might as well put that
into bitcoin, you at least might get something back.

~~~
ge96
Yeah it wasn't so much "looking to grow" just that it would be separate from
cash, another means of having money like items that have good resale value
like Apple computers or something (like a MacBook Air for instance that even
after 3 years later still sells over $600.00)

Yeah I briefly read about mining and how it's not worth it anymore unless you
join a group to mine with.

I don't know, I'm not even able to open up bank accounts anymore/at the moment
so I have different accounts whether prepaid or through job provided bank
accounts or PayPal business account.

Yeap I'm not in a good place at the moment.

Thanks for the information.

~~~
EdHominem
Sorry to hear it.

In that case, where you don't have false goals of runaway success or anything,
and aren't gambling the farm on it, yeah you should throw a few bucks into it.
If you read up on what the differences between currencies are and how that's
likely to impact survivability, you'll be able to pick fairly well.

BTC, Ethereum, and Monero look good, but do your own research. Scams abound.

The most critical thing to remember is that if your currency is "in an
exchange" it might as well not be yours. Funds only become yours,
meaningfully, when transferred to an address whose keys you generated and
which have never been online on an insecure device.

Ideally repurpose an old phone for a wallet and keep it in airplane mode. You
can browse the chain with your regular phone, including monitoring incoming
transactions, all you won't be able to do is sign an outgoing transaction.
Then you either turn on the wallet-phone's connection when it's safe, or
implement a paper-wallet system between the online and wallet phones.

That's overkill for what you'll probably put in right away, but good practice.

