The "Killacycle" electric bike has been running A123 (M1) cells (which are the LiFePO4 ones in DeWalt power tool packs) for some time now, at very, very high discharge rates and is reputed to have not yet blown a single cell.
Last time I checked Killacycle was drawing around 1800 A at about 370V from about 1200 cells (I think they've since added more cells to increase this a bit, in order to hit sub-8 sec standing quarters). Some simple math seems to show that this bike is drawing about 180A (peak) from each cell, so it's clear that these cells do have a pretty good high current capacity (although obviously their capacity will be significantly hit by such high discharge rates).
The major problem seems to be one of supply. A123 do not sell cells, as I understand it, to anyone except a select group of big companies (like DeWalt). The result is that smaller companies, such as those in the ebike world, can't get a look in. Those that do sell A123 packs are apparently ripping them from cordless tool packs, which is not exactly cost effective.
I've no doubt that the Chinese will soon be producing cloned cells that are reliable, but at the moment there does seem to be a big question mark over the quality of some cells/packs sold via Ebay and the like.
I'm running a small SLA pack at the moment, and was thinking about buying some NiMH cells and making a replacement. Having looked into various cell types in depth over the past couple of weeks I'm very much inclined to try and get hold of some LiFePO4 cells of decent quality, as all the indications are that this technology has the best mix of life, capacity and weight at the moment.
One our research programmes has been running extended life tests on several different Li technologies and this also tends to show that LiFePO4 may well be the best available technology at the moment.
Jeremy
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