Part One: Yes, the resistance values need to be fiddled with. No big deal.fechter wrote:The resistor in series with the FET to act as a shunt needs to be a much lower value, like a few ohms.
When the shunt FET activates, it will throw the voltage measurement off because it's in the same string. The voltage monitoring needs to be separate from the shunt.
You need to keep the FET gate at the right voltage relative to the source. You need either a optocoupler or a floating FET gate driver.
Part Two: No, that's not a problem because you do voltage measurement on separate cycles from balancing. Maybe every one hundred cycles you stop and take a voltage measurement... maybe even let the cells rest for a few dozen cycles to let the voltage settle down. That's easy with software.
Part Three: This might be a problem. So you think that the gate voltage needs to be relative to the source voltage. Hmmmmmm.... so if the source at that point in the series of cells happens to be 32 volts you need something like a gate voltage of 36 volts to trigger the FET. That might be a problem. You think the old "common mode voltage" problem will resurface here? (just like with op amps)