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The BatPack (short for Battery backpack) is a wearable item that can provide energy to many low-tier electric tools. It can store up to 60,000 EU, which is essentially 6 times the storage of a RE-Battery.
The BatPack can be equipped in the Chest Slot, which will make it provide power for many low-tier tools:
When a tool is used while the BatPack is worn, as much energy as possible is transferred into the tool. It can also be discharged in machines or energy storage blocks.
The BatPack can be upgraded to the Lappack, which can store 300,000 EU and can charge up any tool.