The Xbox 360 wireless game controller can be powered in one of three ways: connecting the "plug-n-play" wire to the controller and the Xbox; using a standard AA battery pack; or by using the rechargeable AA battery pack. The Xbox's rechargeable battery pack will wear out and stop functioning, and the standard pack can be broken if not maintained well. The solution to both of these problems is to make your own battery pack.
Tape or rubber-band the two AA batteries together so that they are facing opposite directions. This means that you need the "+" side of one and the "-" side of the other at each end.
Insert the coupled batteries into the space for the battery pack on the back of the controller.
Rubber-band or tape the batteries into the controller so that they do not slip or move while playing or transporting.
Slip the three pennies between the plastic of the controller and the batteries on the end opposite the springs. This will provide the conductivity needed to transfer the energy from the batteries to the controller.
Rubber-banding the batteries into the controller will prevent any sticky residue from building up on the controller, and it makes it easier to change out your new battery pack when it runs low.
As always when working with electricity, be very careful not to shock yourself. Do not put your fingers between the batteries and the conductive pieces on the controller.