A123 Battery Technology – LiFePO4

A123 systems has been a big name in batteries since the plug-in revival started again two years ago. One unique property of the A123 batteries is that instead of prismatic cells (that is, rectangular prism), they’re cylindrical, like the AA batteries that go in your digital camera.

Their chemistry of choice is lithium iron phosphate, or LiFePo4. Their current premier cell that they have specifications available for is the ANR26650M1A, or just M1 cell. This cell packs about 7.6Wh in one cylinder about 6.5cm tall (2.55 inches) and 1.5cm in diameter. That means you’d need 2,100 cells to make a 16kWh battery, and that many cells would provide more than necessary power to supply the electric motor.

One of the rumored reasons why GM chose LG Energy over A123 is that because A123 was unable to produce prismatic cells, and GM needed prismatic cells to fit the necessary 16kWh in the Volt without taking up any more room than they already are. However, this is in direct conflict with Chrysler’s assertion that they are working with A123 on a prismatic cell. The M1 is also the cell that the could be in the Raser Electric Hummer H3, based on a reference to the cell in the H3 promotional video.

A123 is happy to tout their cycle life – their specification sheet has a graph showing that at 45°C (113F, not an unreasonable temperature to keep batteries at during usage) the cycle life exceeds 1000 cycles and maintained just under 90% of its original capacity. At the steady rate of decline showed on the graph, it appears the battery could get up to 1,750 cycles until capacity was 80% of original capacity at 1C charge and 2C discharge.

We’ll see if Chrysler can make it out of Ch 11 and the merger with Fiat to create these electric cars they’ve planed on making, or if A123 gets a better dance partner (Ford?) before the prom is over.

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