Here's a theory open to peer-review and open critique: As Otmar has stated "The open circuit voltage at no load, ignoring internal resistance, can indicate SOC of a brick, but SOC is just indicating a percentage of available Ahrs from that brick." My theory is that effective balancing can only occur when the main contactors are open, and this is also the condition when a meaningful OCV can be measured and SOC can be determined. The balancing circuit is controlled by a TI chip, some aspects of which are noted in the Technical Forum here. Once the desired balancing set-point voltage is loaded into the memory registers and the enable register flag is set, then balancing will be turned on whenever the brick hits that value regardless of the main contactor position, e.g. at 93% during charging. But to be effective the contactors must be open, since balance current is only ~ 100 mA for a whole brick. There are 6 bricks per module, 16 modules per 85kWh pack. The balance resistance is 39.5 Ohms. It is left as an exercise for the reader to calculate the total power consumed if the entire pack was balancing for 24 hrs, and compare this to the vampire load.