Vehicle electrical tools repair batteries and electrical circuits. Battery equipment connects, recharges, and jump-starts vehicle batteries. Accessories support and extend the life of the batteries. Wire and cable are used to connect electrical components in a vehicle. Circuits, harnesses and relays may be removed and rewired to repair electrical issues. Switches and spark plugs control the flow of current through vehicle electrical systems. Circuit testers check current flow to verify proper operation or identify wiring problems.