Skip the nimh cells, go straight for lipos- for the same performance/ runtime they cost a lot less, just means you need an LVC (Low Voltage Cutoff) and a lipo capable charger (preferably with a built in balancer). Nimhs will struggle to get you the runtime you want, and will overheat if you gear up from the stock 18/68 the emaxx 3905 comes with... that said they overheat anyway in many people's experience, mine included.