Tesla battery question

[porker928]

If you look inside a Tesla car battery you will see lots of smaller AA shaped bateries (cells) packed together.

So the thought occured to me - why don't they use hexagonal shaped cells instaed of AA shaped?

If they did this they could increase cell density by 9% and thermal dissapation by about 80%.

- Probably a stupid question - but I had to ask.

[TooMany2cvs]

The cells aren't AA - they're 18650-format. A nice standard off-the-shelf format of LiIon battery, a bit bigger than an AA, and 3.7v rather than 1.5v


https://en.wikipedia.org/wiki/List_of_battery_size...

Ain't no point in reinventing the wheel, or adding yet more standards to the existing ones. B'sides, it means they can buy 'em cheap from any one of squillions of manufacturers, so they're not risking being held to ransom from the one company who tooled up specially.

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

[EricE]

Fascinating. I expected the cells to be square, similar to the ones used in various radio control applications:



Google brought me to this link:

http://qnovo.blogspot.co.at/2014/11/31.html

6,912 type "18650" cells, 96 series x 72 parallel

I assume the space between the cells is used for liquid cooling?

[Spunagain]

They fill the gaps with heat transfer compound, this helps move the heat to the water cooling pipes and helps balance the packs temperature as some cells will always generate more heat then others.

[porker928]

Thanks for the replies and info.

Tesla are currently building a huge factory to build the battery packs so this will give them more flexibility on the design.

https://en.wikipedia.org/wiki/Gigafactory_1

I still think a 9% reduction in overall battery pack size would be useful. Hopefully their R&D dept. will read this thread. ;o)

[gangzoom]

Well they have already managed to get a 90kWh pack into the S, and you can now buy a 70kWh pack for the roadster (which is based on the Elise so quite a small car).

If Tesla can continue to make relative small improvements in efficiency/packaging a 100kWh battery pack for something the size of the Model S/X should be appearing sooner rather than later, at 3 miles per kWh, thats 300 miles of range - Which is almost the same as what I use to get out of my old 335i, at £70 a pop.

[TooMany2cvs]

porker928 said:

Tesla are currently building a huge factory to build the battery packs so this will give them more flexibility on the design.

https://en.wikipedia.org/wiki/Gigafactory_1

They'll still be buying in the actual cells, though, and almost certainly using standardised size ones.

[kalibre46]

TooMany2cvs said:

They'll still be buying in the actual cells, though, and almost certainly using standardised size ones.

Cells will be built on-site in combination with Panasonic.

[TooMany2cvs]

kalibre46 said:

Cells will be built on-site in combination with Panasonic.

So there y'go. They're buying the cells in from Panasonic, in such large numbers that Panasonic are building an on-site assembly plant for them.