This is a follow up to my last post (the one where I was getting a short run time with the 110Ma battery.
I went to Battery Plus (a battery store) and look at what they had. I brought the car so I could see what would fit. It looked like I could in fact get 5 AAA 650Ma batteries on the thing. At 3.80 a piece it cost me less then 20 bucks. Brought them home, wrapped them in a little electrical tape and soldered them together. After charging them (they took 630 Ma) I put the rig in the car and started the stopwatch. After 41!!! minutes they finally died. This was on and off running but was VERY impressive. This is with the stock motor and a couple of stops (I would hit something and the battery pack would fall out), but mostly high speed running.
I still need to make the pack look better and put it together with some stiffer tape, but it worked super well.
I also just received today the 300 Ma battery I ordered. It is much smaller and if it give me 15 minutes I will be happy with it. I am looking forward to painting the car this weekend and cleaning up the wires and the battery mounts.