Comment by ericd

4 years ago

Ha awesome! Sorry if I missed it, but I didn't see a mention of the weight of the battery pack by itself, how much does the custom pack add?

6 comments

ericd

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jacquesm  4 years ago

It adds about 7 kg.

  • chrismorgan  4 years ago

    So that’s 7kg extra for your 2150Wh, over the original 500Wh battery? So around 250Wh/kg?

    I’ve been planning a velomobile that I can live out of, and I’ve been interested to observe that by the time you get to one kilowatt hour, I can’t find any Li-ion batteries at all: they’re all LiFePO₄. https://au.renogy.com/renogy-smart-lithium-iron-phosphate-ba... is then about 1280Wh (12.8V/100Ah) for 11.8kg, 110Wh/kg, around half the specific energy (though I haven’t excluded the weight of the controller electronics or any differences in casing). But I understand LiFePO₄ will live longer, and is generally safer (less prone to thermal runaway and whatnot).

    I’m guessing you were going with Li-ion because you were working in the Bosch ecosystem (and potentially for weight as well), but do you happen to have any wisdom to offer about the differences between Li-ion and LiFePO₄?

    • 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.

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  • scotty79  4 years ago

    That's super light for that kind of range!

    • jacquesm  4 years ago

      Yes, that's what I figured. I was a bit concerned that the reduction in range from accelerating the extra mass would be a problem, but that's only about 6% change and once it's going there isn't any difference. It's a bit more cross wind sensitive though due to the enclosed area in the frame.