# Question about cheap LiFePo4 cells.



## frodus (Apr 12, 2008)

Well, they're a PITA to take apart and reconfigure. If you can get single cells, do that. It's a lot of cells to put together too.

And I'm not sure I'm understanding your math.....

to do ~96v (i'd go 32, not 30, but let's use 30) and 12.6Ah, you'd need 30 in series, and 3 in parallel for a total of 90 individual cells. Each pack has 4 in there, so you'd need like 23 packs. That's just over $1k for cells.

Now, they're 30C cells. That means each cell in parallel could do 126A continuous, and 168A burst. There are only 3 in parallel, so you're at 378A continuous, 504A peak. The battery will sag quite a bit at 30C, well below 3V, I'd guess somewhere around 2.8V, so 378A would give about 32kw. At 40C, you might be able to hit 2.6V or so and get right around 40kW. I'm not sure how you got 1200A and 115kw...... 1200A would require at least 6p, and 1200A would be peak. You'd double the cost of the pack.

Now the thing that is MORE concerning, is that for a motorcycle, using about 100wh/mile (could be more or less, this is average from what I've seen, and experienced), 30s3p of these 3.3V 4.2Ah cells would get you about 13.8Wh each, with 90 cells, that's 1.2kwh but that's at 1C, you won't get near that if you're running these at 30C. 1.2kwh is about 12miles if you're only using 12.6A (pretty much impossible for a bike), so you're looking at somewhere around 5-8 miles range (estimating, I can't tell much about these cells because there's no discharge curve for them that I've seen).

Anyway, thats the reality. Per Ah these cells aren't that great. They're $2.60/Ah. Yes they are high amperage cells, but that doesn't mean you get a ton of range on them. They just seem a bit expensive. If you want something that gives range, get Headway or CALB.


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## Bowser330 (Jun 15, 2008)

^^ Good post..


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