[nl12]

When you increase the voltage the amp draw will go down, different motor same final rpm, amp draw will vary based on the load placed on the motor--ie gearing, weight of truck, how far you pull the trigger-- I dont think you would excede the controlers rated amperage, the mah rating of the lipos you pick is related to the amp draw and their ability to deliver current. Assume you pick 4000 mah lipos that are rated at 20c that means the amps they can deliver is = to 4.0ah x 20 = 80amps, with lipos you want to make sure they can deliver the amps you need, if you got low capacity cells it doesnt matter that they are 20c rated cells they will not deliver high amps, same with c rating 8000mah 2c rated cells will not deliver the amps you need either. With the higher voltage setup your average amp draw will be less which also means your runtime will be higher, based on that my opinion is that 4000mah would be fine as long as they have a high c rating 20 is what I would (and have got) get. Again it also depends on gearing, if you are gearing this truck to go 80 mph your amp draw will be signifigantly more than if you gear it to go 55 mph. My recomendations are based on normal gearing not 80 mph crazy gearing. I would personally recomend the 3700 mah apogee lipos on this site I have similar lipos myself, obvously you would need 2 packs, I also have and recomend the hyperion charger and balancer.