There is no easy way to fix the imbalance. Per youtube teardown video the BMS is jbd-hp28sa with passive balancing.OK, let's say this is indeed the case. How do I resolve this without access to the pack and no active balancer? I imagine by keeping the battery at float voltage of 3.4 per cell or 27.2V but for how long?
Would you say, if indeed there is imbalance I should see more current consumption at float voltage as the only cell that is below tries to get charged.
How does charging of the cell that is at much lower voltage work? Is it even possible to equalise such a battery?
I couldn't find the balancing current anywhere but assume that it is not more than 100mA even at best.
Fixing 10Ah imbalance with 100mA balancing current would take 100 hours or about 5 days and we don't know if the balancing current is even 100mA.
If you have adjustable lab power supply set it to something like 100mA and 30 volts and let the battery charge until it hits OVP.