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Battery Choice

Battery Choice

Why does tesla choose to go with Lithium-ion instead of Lithium-Polymer batteries? Based on what I'm seeing form the general battery data sheet is that, Lithium-Polymer has a much higher energy density than Lithium-Ion; wouldn't this decrease the amount of batteries needed in the car hence decrease the weight of the car overall?

Jolinar | December 3, 2013

I don't know what data you look at, but Tesla is using Panasonic 250Wh/kg cells, which are one of the best comercial viable batteries you can get... Do you know about better? Let us know...

Tugvow | December 3, 2013

I think that this may have a reason, just on wikipedia though; "In recent years, manufacturers have been declaring upwards of 500 charge-discharge cycles before the capacity drops to 80%" I would say that that is significantly less cycles then consumers would be willing to have for a car, even at ~300 miles a charge, that's only maybe 140,000 miles or so, accounting for the decrease in capacity over time.

Tugvow | December 3, 2013

reading further, there seems to be a lot of 'higher risk' factors also, such as overcharging can cause explosions etc. I think there would need to be more of an evolution in li-po batteries to make it more worth-while the li-ion, and by that time, li-ion will probably be better too.

Joshua Burstyn | December 3, 2013

Based on what I've seen Tesla chose the 18650A cells from Panasonic and customized them for automotive applications.

More specifically they are not using traditional Lithium-Cobalt chemistry but rather Lithium Nickel Cobalt Aluminum Oxide. This provides excellent specific energy, specific power and long life. Some would say that NCA chemistry is more volatile than a lithium polymer or lithium titanate battery type. The engineers at Tesla thought of this concern though and have created isolated zones within the pack as a whole. Additionally the coolant is designed to solidify in the event of a thermal runaway, preventing adjacent cells from venting violently.

All in all the choice of battery was ideal for the performance and longevity of the pack. The drawbacks of this chemistry are that the cells must be carefully protected and that they remain more expensive than some other types. You can read some more info here as well:

http://batteryuniversity.com/learn/article/types_of_lithium_ion

Anthon Li | December 4, 2013

@Jolinar I was basically looking at A123 Systems and how their Nanophosphate Lithium-ion battery technology has been used in many Motorsport companies throughout the years.I'm guessing its not used by Tesla due to its production cost; being a smaller company compared to Panasonic, the price of production should be higher.

Anthon Li | December 4, 2013

@tugvow Yes,I agree, Lithium-Ion definitely has the advantage in terms of experience; it became clearer to me after I had a chat with a senior lecturer that Lithium-ion is chosen in most cases due to its reliability. I think Tesla made the right choice going with Lithium-ion, but in years to come, I think Lithium-Polymer would dominate the market, unless they come up with something better than these two batteries.

Anthon Li | December 4, 2013

@Jewsh Great info, thanks! I have done some research and have found that the reliability issue of Lithium Polymer batteries always tends to turn up; even though the Lithium Polymer has a higher energy density (approximately 1.5 time more), I believe it is not as reliable yet compared to the Lithium-ion.

Timo | December 7, 2013

@Anthon Li, reason why Motorsport (and PHEV) companies use A123 batteries is their power density and very good cycle durability, not energy density. Those batteries they use have approx 1/3:th of the energy of traditional high energy Li-ion.

Brian H | December 7, 2013

No car has been involved in more high-profile whoops-de-do than Gallardos. Given that the last one left the factory last month, the value of those on the road may start to rise — if their owners can keep them in one piece.

Get the last one, before it burns!

Brian H | December 7, 2013

Oops, wrong tread. Solly.

Car t man | December 7, 2013

So you didn't just make a mistake at a single letter or word, but at the entire post! Brian, I don't know where to begin this payback opportunity.
And you can't even edit or delete.. :)

As for the topic of batteries.

I have automotive Li Poly batteries (Kokam) for a future high end performance conversion. They are lighter, more energy and power dense, but also more dangerous. If you pierce it, overcharge it, etc. they can be trouble.

Hopefully this is fixed down the road. The idea with Li Poly was that in devices, it could be used in the entire housing of a device, etc.