[brijar]

I think he means if you plugged a 2s A123 directly into the Rx's Batt slot, it doesn't run it very well.
Doesn't the 5700 handle up to 12 NiMH cells? That is 14.4 volts. 4s A123 is only 3.3v*4 = 13.2v, which is less than the NiMH's rated voltage.
What I am probably going to do is cut the Dewalt pack up into two 2s packs and two 3s packs. I'll run a 3s pack mostly in the Rustler, and if it is safe, run a 4s setup every once in a while. For my boat, I'll put a 2s on the BEC side of the ESC, and probably a 2s on the other side too, but use a 3s on the non-BEC side when I need to race my neighbor's Villain EX (completely stock, 12 Radio Shack 3000 cells:005:). Theirs is fast, being new and all, but I have specially designed carbon fiber props, lower turn E-Maxx (non Marine) motors, more water cooling, better batteries, and more batteries. I should have no trouble beating them:027:.
@CPB, The Titans may get hot, so I would at least check them during the middle of a 2p run. I'm just going to do what you suggested, running 5s1p, then just switching that set out for the other set. If it is too hot, I'll let it cool some.
Does anyone know how A123's and water react? What if I were to flip my boat and some water gets in around the cells?