That's not correct.
The correct procedure:
- turn off circuit breaker
- unplug balance leads connector
- measure cell 1 voltage between pin 1 and pin 2 of the connector
- measure cell 2 voltage between pin 2 and pin 3 of the connector
- measure cell 3 voltage between pin 3 and pin 4 of the connector
...
- measure cell 8 voltage between pin 8 and pin 9 of the connector
- replug the connector
- turn on the circuit breaker
It doesn't matter which way around you put the voltmeter leads, the only difference will be a sign "-" on the screen but we don't care, we just want the voltages
Previously I didn't say to turn off the circuit breaker and to unplug the connector because you can do the measurement without unplugging the connector but it's a bit more complicated if you're not familiar and there is greater risk to make a short-circuit between the connector pins with the voltmeter leads, so yeah, don't go this route.
Yes, but you need to find the same connector which is used here and do the Y yourself.