How Does a Booster Cable Work?

Connects Two Car Batteries

A booster cable is a simple device used to jump-start, or recharge, a dead or discharged car battery. Made up of thick-gauge electrical cable coated with rubberized insulation, a booster cable transmits electrical current from a live battery in one car directly into a dead battery of another car.

Connects Directly to Battery Terminals

A booster cable has four metal connections--two on each end of the cable. Each end is made up of a positive and a negative connector. The positive connectors are attached directly to each car's positive battery terminal; the negative connectors are attached directly to a metal surface in each car's engine compartment--a bolt, a metal housing or any metallic part of the engine.

Transmits Current From Good Battery to Dead Battery

After the booster cables are connected, the good battery in the running car transmits electrical current directly into the dead or discharged battery of the nonrunning vehicle. The current flows from the battery directly into the metal connectors of the booster cable and then flows along the booster cables and on into the second battery.

Booster Cables Removed After Adequate Charge

The battery of the nonrunning vehicle normally receives sufficient charge to start after a few seconds of being connected to the booster cables and second car battery. After the car starts, the booster cables are simply removed one side at a time. Normally, the negative connector is removed from either vehicle first, followed by removal of the positive connector from either vehicle.