[Doombringer]

And also, the total power is equal to the product of the Voltage and Amperage

P = UI

So you either have a higher voltage or a higher amperage to get the same power. This is why they usualy go with higher voltage on Ni-Mh cells, because they are not made to provide a high Amperage, as opposed to Li-Po cells.

The problem with higher amperage is that Heat dissipation is only affected by either Resistance or Amperage, not voltage. This is why the hydro company transports all the electricity at very high voltages, to minimize the loss in power (heat).

P = R*I^2

The mAh means milli-ampere by hour. If you have 1000 mAh, it means that the battery can provide 1 ampere (1000 mA) for 1 hour before being drained out. So a 4000 mAh is not a battery that is more powerful, but it is a battery that will last longer that the other one. For exemple either 4 amperes for 1 hour, or 1 ampere for 4 hours. I think you got it, it's real simple.