grenade6,

Have you ever seen an A123 cell? I'm just asking because those things are huge and heavy. They are about the size of an alkaline C cell battery and weigh 70 grams each. You're talking about 2.5 pounds of one brick (literally) of a battery pack.

Anyway, if you are going to run that many cells in a truck, I'd shoot for a lower kv motor. Perhaps something in the 1100 to 1200 kv range. I run a 1515/2.5d in my 8ight T on 18.5v and it'll do 50 mph. I think that running the 2.5d on that much voltage for any sort of extended running might result in lots of heat.

I'd go one of two ways. Either the 1515/2.5d on a 5S2P A123 setup, or your chosen voltage with either a 1515/2y or 3d.