The RE-Battery, (Rechargeable Battery), can store up to 10,000 EU. Placing it in a BatBox, Generator, MFE, MFSU, Solar Panel, any Solar Arrays or a Charging Bench will charge it. You can charge the RE-Battery and take it with you to charge any electric tools, such as an Electric Wrench, Electric Treetap, Electric Hoe, and a Mining Drill. They are charged by right-clicking while holding. It can also be used to power machines from IC2, such as the Macerator, Generator, or the Electric Furnace. It is not compatible with BuildCraft Power or RedPower Power as it is not from any of those mods.
When you have the RE-Battery in your inventory, pressing the sort button (added by Inventory Tweaks) will sort and then immediately unsort your inventory. If you are in your inventory when this happens, you will be holding the RE-Battery as if you clicked on it from your inventory. If you are not in your inventory when this happens, the RE-Battery will be thrown on the ground.
Sometimes, if you put two full RE-Batterys in the Crafting Table in SMP, it can craft into one.
Because the uncharged RE-Battery and the charged RE-Battery have different data values, you will need a slightly charged battery for most recipes. For instance, when crafting a BatPack, using a chargeless RE-Battery will not work, and you will have to add a little power first.