Comment by jacquesm
4 years ago
Yes, LiFEPO4 would have been preferred but the Bosch BMS doesn't know how to deal with that chemistry. There are some interesting developments, have you looked at these?
https://www.youtube.com/watch?v=kYx097cVR48
If I had free pick of chemistry I probably would have gone with those. 250 Wh/kg sounds about right, I'm running the cells in a very conservative regime though, topping them up to about 80 SOC and discharging to about 20, so my effective range is smaller but the battery life-span will be very long, many thousands of cycles. The balancer also helps with that.
LTO definitely sounds very interesting, and I’ve noted it down for further investigation, but on brief examination it’s not sounding particularly compelling for my particular use case over LiFePO₄: I probably wouldn’t actually benefit from any of the places where it’s superior. Life span, for example: sixty years of daily discharge is nice and all, but LiFePO₄ should already easily last me a decade or two (time will kill it, not cycles), and I don’t think it’s useful to forecast beyond there. And I don’t need its more rapid charge or discharge. And so the main thing that’s left is its lower specific energy, and I’m not fond of the idea of lugging around an extra dozen kilograms per kilowatt-hour. (Its lower energy density wouldn’t be a problem; I can readily allow a few extra litres in the design, which you couldn’t do on an e-bike.) Stack all that on the more restricted range of options unless you’re willing to deal with unknown Chinese entities and AliExpress, and I expect I’ll end up staying with LiFePO₄.
For typical off-grid house power needs, on the other hand, LTO sounds extremely compelling.