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Battery Chemistry

Hi all,
I was just wondering what the battery chemistry was in the Model S. I know that it is different for the 40kwh/60kwh and 85kwh battery packs. Just wondering so I can do some research on the reliability of the Cell chemistries. I'm pretty sure it's been posted in the forum before but I can't find it.

Other sources, such as the Stanford talk and paper on the Tesla batteries suggest that part of the modification is battery management/manage to prevent thermal runaway.

nickjhowe, you rock. Even if it's not the optimized cell I now have an idea for how the cells degrade with cycle number in lab conditions. Optimally (and optimistically) it looks like it lost 500mAh capacity over 300 cycles (16.7% loss). or 99.94% cycle efficiency. The trend doesn't exactly appear linear (linear wouldn't make sense regardless), kind of like an upside down ln() function. I tried to make somethings fit in excel but failed. Anyways with a linear trend you can expect to see full cell degredation after 1800 cycles?

Hi All,

I vaguely recall reading some time ago that Tesla's pack have redundancy "design in" with bypass of non performing cells. They are the only ones in the EV industry who is able to balance 8,000+ cells. There has never been a report of packs fire from Tesla.

There is much talk about active balancing concepts and using smart chips to balance individual cells voltage during cycling. Could someone out there shed some light as to how Tesla manage to monitor and balance 8,000 + individual cells. How the bypass of non performing cells is carried out?


Tesla and Boeing use the most unstable and flammable chemistry. Lithium Cobalt is used due it's high energy density. Check out the link:‎

Evnut, that's not accurate. I very recently watched Elon speaking about the battery, he listed the elements Lithium, Cobalt, Nikel and Aluminum. After a very quick search I learned from an MSDS the chemistry was the following:

Anode: Carbon (most likely including something like carbon nano fibers to help durability)

Electrolyte: 1.2M LiPF6 in some mix of Ethylene carbonate, Propylene carbonate, Di-methyl carbonate, Diethyl carbonate.

Cathode: LiCoNiAlO2.

Thanks everyone for the effort. Seems I was the one who solved it!

It is likely true, that the chemistry is a bit altered, albeit not necessarily. Companies sometimes say they use customized blends of
components and raw materials, to throw off competition and to
provide a more upscale feel to the product.

With boeing, it isn't as simple. It depends on what you view
as a battery. Cells, BMS and charger or just cells, etc.

I think BMS mistreats the cells badly in those incidents.
Those cells aren't the kind that tolerate faults.

Just came across a fantastic (where "fantastic" = highly technical) video about Lithium-ion battery degradation that specifically compares the chemistry of Tesla (or Tesla-like) cells to those used in the Volt and Leaf, and (not unexpectedly) the fantastic choices that Tesla has made.

At around the 27 minute mark it shows the key performance differences between the Tesla and other cells, indicating that the "coulombic efficiency" vs charge cycles of the thermally managed Tesla battery pack is nearly flat - in other words there should be almost no degradation of performance over time. But don't jump to 27 minutes without watching the first part otherwise it won't make sense (unless you are a battery engineer).

That Dalhousie video is worth watching all the way through!
Lots of insights throughout.

How did you miss this video til now? Maybe JT should put it in his FAQ His protege works for Tesla now.

We can rule out lithium-polymer right away and I'm reasonably sure we can also rule out lithium-cobalt. That stuff is nasty. If any alterations were made to what is called "lithium-ion", nobody is talking but I would assume there were some minor chemistry tweaks. That said, Tesla is not about to push the envelope as Boeing did for reasons which are obvious. This would be the same reasoning that Toyota used in choosing Nickel-Metal Hydride as it was a known tech with predictable response characteristics.

From watching the video it looks like there are potentially still major gains to be achieved by tweaking the additives in the electrolyte.

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