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Old 05-13-2015, 04:11 PM   #15 (permalink)
RedDevil
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Red Devil - '11 Honda Insight Elegance
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True - nevertheless a string of 36 cells could get damaged if the voltage over it drops to from 117 Volt (fully charged) to 107 (average OEM pack voltage), if one of them is discharged deeper than the rest.

Bottom balancing the cells once in a while should prevent that.
But then I'd need to charge them on the string while monitoring each cell like a hawk, as LiFePO4 voltage tends to hold steady during charge and then suddenly go through the roof, damaging itself, when full.

I might pair each cell with a small Lithium-ion cell to buffer the overcharge differences.
When the pack is nearly full the voltage over all cells will rise more or less simultaneously, so the charger could just have a voltage cutoff.
But I'm scared of what would happen if a Li-ion cell fails.

I could use a BMS. But I don't have any experience with those and stories of packs killed by a faulty BMS make me wary.

If only I could just buy a black box with one dial to set the desired voltage and another to set the max current and hook that up...
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