Battery Boxes are used in RedPower to store and regulate bluetricity.
When placed next to a machine, or connected by blue alloy wires, it will regulate the flow of bluetricity. If there is insufficient power, it will supplement the flow by draining its stored energy. If there is greater than sufficient power, it will store the overflow until full.
Right-clicking a Battery Box shows an interface with the current network power level, the box's storage level, whether energy is flowing in or out of the box, and two slots for BT Batteries. If a battery is inserted into the top slot, it is charged until full at the expense of the box's storage. If a charged battery is placed in the bottom slot, its power will be drained as needed to maximize the box's stored energy. Battery boxes can also receive power from any side and release power from any side also.