Vehicle electrical equipment and tools are used to keep batteries and electrical circuits in good working order. Vehicle batteries are connected, recharged, and jump-started using battery equipment. The accessories help to support and extend the battery's life. In a car, wire and cable are used to connect electrical components. To fix electrical problems, circuits, harnesses, and relays can be removed and rewired. The flow of current through car electrical systems is controlled by switches and spark plugs. Circuit testers measure current flow to ensure proper operation or to pinpoint wiring issues.