[BobEdwards]

Thanks, Ryland, for your prompt reply and useful thoughts on my query.

As I see it, if I want 144V, I am committed to 45 LiFePO4 cells in any case, so my idea doesn't increase the number of connections between cells, just adds one extra connection to the alternative driver board.

Thinking this through a bit further, my 96V @ 90AH battery will give a 10C current of 900A. My motor can take up to 200A continuous (@144V) or peak at 600A. 600A @ 96V gives me up to 59.6kW (for short periods).

The series-connected 48V @ 40AH battery will give a 10C current of 400A. When this is in use, the 40AH cells will limit the motor current, so I can get up to 400A @ 144V or 57.6kW (almost the same), but the extra volts will give me more RPMs, so will only be needed when already at speed.

What does this gain? I save almost A$1000 in LiFePO4 cells, over 22kg in weight and some space savings. The cost is the development of a controller that can drive two sets of driver boards (but only ever one at a time!).

Worth doing? Am I missing something important?