I have a battery which will remain connected in series, and I want to have an option to connect / disconnect the balancing leads electrically - something like this:
which will connect the batteries when the "active" line is driven high from an external power source (not the battery stack, only connection between the two as what's shown here, i.e. "common" ground when the connection is made, and high resistance when off, but then disconnect them when it's driven low (the resistor bridges are going to an ADC to then calculate each cell voltage)
The problem with this circuit is that when the active line is low, the gate voltages on the P-channel mosfets ends up being the same due to the resistor dividers that I want to remain there, and thus I need mosfets that can handle a large gate-source voltage difference. I am looking for a way to "chain" them or stack them in a ladder-like fashion where the voltage that the mosfets needs to handle is not related to the # of cells in the stack - what would be the best way of doing this?
P.S. - not shown here but I want to be able to actively balance the cells as well, so once I figure out their voltages I can selectively charge/drain the cells via these same balancing lines, thus I want low RDSon mosfets, which tend to have lower voltage tolerances