Dave,

I used 30v 9ah Nicads on 2 Bosch 750s towards the end of the last season, and found that they had plenty of capacity for a 5 minute fight. In fact I rarely used much more than 1/3rd of their capacity.

I was using 4QD NCC60s as the motor controllers and not Roboteq, and that will reduce the peak current absorbed. However I was using 30v and not 24v.

I guess that the answer will be decided by how much pushing you will do. I believe that other peoples experience of operating two Bosch 750s at 24v with a Roboteq controller is that there is a minimum battery duration for 9ah of 7 minutes.

Jeremy