I have latched onto a123's for some reason and so I fitted my new Apache with a 2s2p A123 pack. Nominal voltage is 6.6V and with the 2p setup the internal resistance should be quite a bit lower than a nimh pack. My calculations show the internal resistance being 1/6 of a good nimh pack. The two battery packs weigh 11 ounces w/o the Y adapter.

Any way... I did a test drive yesterday on a 2s pack. Both packs in the boat but only using one pack and the boat scooted around nicely. It had a nice rooster tail and came up onto plain quickly. Today I tried it out with a Y adapter and it worked out nicely. Obviously the run time was longer and it is hard to say if it was any faster. Motor temp was about 53C and the ESC was in the 50+ range as well. Mostly wide open throttle although I was trying to back off when I would think of it. Boat does appear to be listing to the right some. Torque?

How are these temperatures? Should I prop down? I would hate to burn through motors or ESC's to frequently.

The only downside I've seen with the a123's so far is that if the packs voltage drops to the 3.4V/cell range the ESC won't arm. But if charged and maintain close to 3.6v/cell then it arms no problem.

My end goal is to try to use the 2s2p setup for brushless. I figure I will have to go with a higher KV motor and find a ESC that will be happy in the lower 6v+ range. As I look at the setup more I may be able to squeeze a 3s2p a123 pack in there.