If I give a BMS slightly lower volts, will it still balance?

marka-ee

100 W
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Mar 24, 2020
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I have a new kaabo scooter that seems to want to charge to 4.2 volts per cell, something I really don't like at all, as I value cell life over maximum capacity.

My question is: I see some charger being sold that supposedly charge to 90% or 80% by switch , for these types of scooters. Can you really feed a BMS a slightly lower voltage and still expect it to do it's balance function ? It's probably a generic type 48 volt BMS, built into pack.
 
Thanks for the detailed answer. On my bike I have been charging to 4.1V per cell, and only rarely discharge to 3.4 V per cell, with no BMS at all. It's been ok for 3 years now. But these are higher quality cells.
For the scooter, what if I do similar to your suggestion and charge to a voltage of about 4.1 by pulling the charger early and once in a while let it do a full charge to allow the bms to balance the battery? Maybe a good compromise?
Hacking a programmable bms into the pack would be ideal but would invalidate the 1 year warranty.
 
On the bike, which is 36 volt (10s) I charge with an rc charger but bulk charge. Now and then I check the cell to cell voltages, and they are remarkably close. But my main concern is the scooter, which is new. If I pull the charger off when it hits 4.1 x 13 volts but once every 10th charge I let it do it's full 4.2V balancing would that be sufficient?
Yes, batteries are a consumable, but non-toy EV's like cars absolutely do not charge to 100%. They have warranty claims and reputations to uphold a bit more than smallish china scooter companies who have to rely on off the shelf china bms's and packs. Virtually no engineering department or English user manual translators :) My old scooter, a m365, did only charge to 4.1 and has a bms that communicates to the motor controller as well as an app or i2c bus to let you read out cell voltages. Anyways, full charge every 10th a good strategy?
 
If you want good longevity and proper balancing

buy an active balancer that will do the job in a short time (at a decent current rate) and at any SoC/voltage point you desire.
 
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