I check mine during the last stage of charging. I watch for when the charger is only pulling 4-5W from the wall and then take my measurements. I've been doing this each month so I have some data on what happens over time.
Gizmo, I would LOVE to hear more about your pack balance over time. How many months have you collected, and have you had to 're-balance' at all.... or what your criteria is for out of balance enough where you want to re-balance?
Just going back a few posts here, it sound like you may be using very much the same process I am in waiting for end of charge, a brief settling period while still plugged in to slow the settling out of the the knee, and then trying to get all cell measurements while they are up in the top knee and showing any balance issues....
It sounds like you are a top balancing, non-shunt BMS person?
oohhh, and I am using a CA as well. Bad news for me is that with a 120v nominal pack voltage, the internals are 'oversaturated' according to Justin at ebikes, which is why I cannot get the amp-hr counter to zero and stay zeroed, and also why I cannot tune the voltage reading to match voltmeter... it 'pegs' and aparrently needs n internal resistor changed from 220 ohm to 330 ohm? Have you done this?