When dealing with electric current through a circuit (in this case, the battery), the ONLY affect that the battery has on the current is the voltage. The properties of an electrical circuit is expressed by Ohm's law: V÷R=I, where V is the voltage, R is the resistance, and I is the resulting current in Ampere's. The Amps is the PRODUCT of the battery's voltage and the resistance of the motor.
The Amp rating on a battery is how much current the battery can produce before the battery itself begins to be damaged. As long as the current is below this rating, all is good. Think of the battery kind of like the output hose on a pressure washer. If your washer is pushing the water out at 60psi, and the hose it's going into is rated to 120psi, then will there be any problems? Obviously not. But, however, if the hose is only rated to 30psi, then what will happen? In the case of the battery, the result is the videos that flood the internet on a laptop battery spontaneously combusting. Even though that is a slightly extreme example of what can happen, I don't want something like that happening inside my gun. If the motor's resistance drops (let's say that it is in a near-stall situation) to the point that it should draw 20A, then it WILL draw 20A. It doesn't matter if the battery is only rated to 15A, the current will still be 20A. I don't know about you, but I feel better with the Amps rating on my battery being 2-3 times higher than the expected load (my battery is 55A constant, 75A burst).
The mAh rating is just how long a battery can output a given current. It's like with the water system in a house. If you upgrade your water heater to one with a bigger tank, but is the same in all other ways, then will it affect the pressure/temp of your showers? No, but it WILL affect how long you can take the said shower before you lose hot water. So, the ONLY difference you'll see going from a 1600mAh 11.1V 20A battery to a 2200mAh 11.1V 20A battery is that the 2200mAh battery will let you fire more shots off before you need to recharge.
The one thing about a battery that could damage a gun is the voltage, and so long as you use a 11.1V three cell LiPo, the voltage shouldn't be an issue. Going higher, however, can damage your gun. That is assuming that the motor will draw enough Amps to damage the gearbox before the fuse pops, which shouldn't happen.
If anyone has anything to add, then please feel free.
Edited by NumenoreanBlood, 25 March 2010 - 11:58 AM.