Most controllers have banks of capacitors inside that help to smooth current flow. The capacitors gradually discharge when the controller is shut off, and recharge when it's switched back on.

To protect them from potentially life-shortening high amperage current in-rush when the controller is switched on, a precharge resistor is used to slow the flow of juice to a more capacitor-friendly rate.

In the ForkenSwift, the resistor we're using is one of the forklift's spotlight bulbs.