The battery box stores electrical energy. The storage unit outputs power from its side through the dark output. It is charged from the opposite side through the red input on the block. By default, it can hold up to 5MJ and transfer 43.08kW of power. This can be upgraded using capacity upgrades. If you use three advanced battery upgrades, this will put the max possible capacity and transfer rate for the battery box at 56.95MJ and 490.7kW
Do note! The battery box is special in relation to power input and output. Unlike the other machines in Electrodynamics, the battery box can transfer any power. That makes it perfect as a power converter.
Storage (5MJ) / Transfer (43.08kW)