Originally Posted by Telrin
I'd like to know how the voltage protection circuit works before agreeing with you.
If it is acting to stop charge current reaching the first cell when it gets to 4.2V but lets the other cell still charge then you effectively have a crude balance circuit.
But both cells are charged serial. Cut one BMS the power then cut it for the second cell too.
Not a crude balancer more a inbuild debalancer.
The part charged cell debalanced with the time more and more.