I'm using a 2s BMC to charge a 2s2p lithium battery pack (7.4v, ~6Ah). The output of the charging circuit is the same as the input - they're not separate. As a result, when I want to charge the batteries, I just hook up 8.5v to the +P and -P terminals and let the BMC do its thing.
Is this bad practice? Is there any potential damage to the batteries if I am charging them AND the power from the charger is powering the circuit (the circuit normally powered by the batteries) at the same time?
I don't believe so off-hand, but I've heard that too much ripple on the voltage supply for the BMC can cause issues where it has a hard time detecting the charge status of the Li-Ions.