The RE-Battery is an early-game Industrial Craft 2 item. In addition to being used in many of the crafting recipes for Industrial Craft 2's various tools and blocks, the RE-Battery can be used to recharge them, or simply as portable EU storage if needed. Placing a RE-Battery in the top slot of any generator, BatBox, MFE, MFSU, or a Charging Bench will recharge the RE-Battery. One RE-Battery can store up to 10,000 EU.
Holding the RE-Battery and right-clicking will recharge any electric tools in the inventory. This includes the Mining Drill, the Diamond Drill, the Chainsaw, the Electric Wrench, the Electric Hoe, and the Electric Treetap. In addition, the RE-Battery can be used to power any Industrial Craft 2 machine, the BatBox, MFE, or MFSU.
When used in crafting any of the above tools, as well as the BatPack, the charge level of the RE-Battery determines the amount of charge the item will have. A charged RE-Battery will produce a charged item, while an empty one will produce an item with no charge.