Updated 6 October 2026.
A flat battery is inconvenient, but a jump start is not suitable for every vehicle or situation. Incorrect connections can cause injury or damage electronics. The safe procedure is the one specified for your vehicle and the equipment you are using.
Check the location and battery first
If the car is in a dangerous position, prioritise getting help rather than working beside moving traffic. Do not attempt a jump start if the battery is visibly damaged, cracked or leaking. Keep flames and sparks away, and contact roadside assistance if you are uncertain about the battery's condition.
A car that will not start does not necessarily have a flat battery. A technician can check the battery and charging system rather than relying on repeated starting attempts.
Read the instructions for both vehicles
Consult the owner's manual before connecting anything. If another vehicle will supply power, check its manual too: some vehicles must not be used to jump-start another car. For a jump pack, follow both the vehicle instructions and the pack manufacturer's directions.
- Confirm that jump-starting is permitted and that the equipment has the correct voltage and capacity.
- Identify the approved jump terminals and earth point. They may differ from the battery terminals or be located away from the battery.
- Follow the specified preparation, connection, starting and disconnection sequence exactly.
- Keep leads clear of moving parts, and never allow the clamps to touch each other.
There is no universal instruction to connect both black clamps directly to battery-negative terminals. Use the connection points specified by the manufacturer. If the instructions are missing or unclear, stop and ask a roadside technician.
Extra care with hybrids and electric vehicles
Do not confuse a vehicle's low-voltage auxiliary battery with its high-voltage traction battery. Never connect jump leads to high-voltage components or orange high-voltage cables.
Some hybrids and electric vehicles have a manufacturer-approved low-voltage recovery procedure, while their use as a donor vehicle may be restricted. Check the exact model's manual; the procedure for a conventional petrol car is not a substitute.
After the car starts
A successful start does not establish that the battery is healthy or fully charged. Driving for a fixed period, such as 30 minutes, cannot guarantee a full recharge. Ask for advice on testing and charging the battery and investigating why it went flat.
For further guidance, see NRMA's flat-battery advice and RAC's explanation of recharging a flat battery. For the actual procedure, always use the manufacturer's instructions for your vehicle.
