Project Evo

[MetalMan]

Generally, a Lipo will be about 1/2 the weight of NiMh in the same power rating (voltage times amps). For example, Kokam 4s 3200mah is ~400g, and a 12cell GP3300 pack is ~780g. If you don't need all the power that a GP3300 (or higher) has to offer, then you could get a Lipo pack that is smaller that would suit the current that the motor requires that would be ~1/3 less weight than GP3300 (for the same voltage).