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bmw I3 batteries capacity

1904 Views 5 Replies 4 Participants Last post by  cricketo
I am working with 2 modules of BMW I3 batteries 84 volts in series using 21 of 24 cells. 60 ah batteries
NMC chemistry I believe. discharging to 3.5 volts resting and
charging to a resting of 4.06 algorithm #156 on a delta Q charger 85.5 voltage (4.07 per cell).
I am charging and tracking my kilowatts back in with a kill a wattmeter.
putting about 3.4 kWh back in It seems I should be getting more out of these packs. 60 x 3.8 x 21 = 4,788 watt hours. Am I not charging high enough or should I be discharging a bit lower? 3.5 volts resting for this chemistry was recommended by folks here on the forum. the next available Delta Q algorithm I have is 87.588 volts which is 4.17 volts per cell. It is short of the maximum of 4.2 volts per cell.
So would that be safe and worth it? Cells are tracking with each other very nicely.
Not like Lifepo.
these are in a ukrainian sidecar motorcycle:D
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I was under impression nominal for them is 3.7, not 3.8. Either way, two other things to consider - the charger is not 100% efficient. Since you're tracking power on the AC input side, not the same amount of power will be going to the battery pack. Then these are salvaged cells. There are specs, and there is the fact they're used.

But yeah, look up some charts for NMC cells, see where 3.5v puts you :)
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