A dead or failing battery can leave a vehicle unable to start at the most inconvenient time. Knowing how to jump-start a car with a bad battery can provide a temporary solution, provided the battery and surrounding components are safe to handle.
The process requires jumper cables, a suitable donor vehicle, and careful connection of the terminals in the correct order. However, a damaged, leaking, swollen, or frozen battery should not be jump-started, as it may create serious safety risks.
Before learning how to jump-start a car with a bad battery, inspect the battery carefully. Do not proceed if it is cracked, leaking, swollen, or frozen. Turn off both vehicles, engage their parking brakes, and keep them from touching.
Connect the red jumper cable to the disabled battery’s positive (+) terminal, then attach its other red clamp to the donor battery’s positive terminal. Connect the black clamp to the donor battery’s negative (−) terminal.
Attach the remaining black clamp to an unpainted metal grounding point on the disabled vehicle’s engine block or chassis, away from the battery and moving components. Confirm that all connections are secure and correctly positioned.
Start the donor vehicle and allow it to run for several minutes, then try starting the disabled car. If it starts, leave both engines running briefly before removing the cables in reverse order. Drive or charge the battery afterward.