Powercells store massive amounts of power. They can be placed either individually, or they can be placed next to one another to form a multiblock structure. Powercells will automatically distribute RF between themselves and their neighbors, and will join up into a multiblock regardless of tier.
Powercells have no UI, but can be configured to input, output, or ignore power by hitting the desired side with a smart wrench in Wrench Mode. Blue is input, Yellow is output, and a blank side is neither.
By default, the Powercell (low) can hold 500,000RF each.
McJtyLib · copy nbt
By default, the Powercell (Medium) can hold 4,000,000RF each.
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By default, the Powercell (high) can hold 20,000,000RF each. That's a lot of RF!