The Industrial Coil is a block from RotaryCraft that stores power in the form of Joules.
To charge the Industrial Coil, an engine must be placed facing into the green side of the coil. The coil will then begin to charge. However, if a low tier engine is used, the coil will only gain a minimal amount of power. This is because the Industrial Coil requires ever increasing amounts of Torque in order to charge. To use a lower tier engine to charge the coil, use gearboxes to make the engine output the maximum amount of Torque possible.
Here is a graph showing the Power and Torque requirements for specific amounts of power stored in the Coil.