I just received your P-51 kit from Todd's models. I beginning the assembly process. I have several 8 cell 100mah NIMH batteries I use in other models. You only mention 6 & 7 cells. Is that because of weight or is 8 cells too much for the small motors?

From : Don Stackhouse

It's a judgement call based on the treadeoff between more power and more weight. The P-38 does very well on eight cells, although the flight times are lower. The single engined models like the P-51 have less wingspan, which makes them more sensitive to small weight increases. If your Mustang comes out a bit heavy, a seventh cell can help. However, by the time you add an eight cell, the returns from the extra power in comparison to the extra weight are starting to diminish. In addition, on the P-38 we are feeding two motors, so the cell voltage is reduced. The eighth cell therefore gives you about the same system voltage that a seven-cell pack would have in a single-engined model. If you try running eight cells with one motor, the current might be high enough to start significantly cutting into the life of the brushes. 'Course if all you want to do is bore really impressive holes in the sky for just a few minutes at a time, you have a BIG flying area where you don't have to worry about making tight turns, and you don't mind replacing motors regularly, you might be happy with eight cells.

Don Stackhouse
DJ Aerotech