A flat car battery is one of the most common roadside problems. Jump starting is straightforward if done correctly, but the wrong order of connections can damage sensitive electronics on modern cars.
What you need
Either a set of jump leads and a second vehicle with a charged battery, or a portable jump starter pack (a lithium battery pack with built-in leads, available for £30 to £80 and useful to keep in the boot).
The correct procedure with jump leads
- Park the donor vehicle close to, but not touching, the flat vehicle. Both should be switched off.
- Connect the red (positive) lead to the dead battery positive terminal (+).
- Connect the other end of the red lead to the donor battery positive terminal (+).
- Connect the black (negative) lead to the donor battery negative terminal (-).
- Connect the other end of the black lead to an unpainted metal earth point on the dead vehicle, away from the battery. A bolt on the engine block or chassis works well. Connecting directly to the dead battery negative terminal is the traditional method but is less safe as batteries can emit hydrogen gas.
- Start the donor vehicle and let it run for 2 to 3 minutes.
- Try to start the dead vehicle. If it starts, run both vehicles for a few minutes.
- Disconnect in reverse order: black from earth, black from donor, red from donor, red from previously dead vehicle.
What to avoid
Do not allow the leads to touch each other or the wrong terminals at any point. Do not connect red to negative or black to positive. Do not use a vehicle with a significantly larger engine as donor without a current-limiting lead set, as the voltage surge can damage the electronics of the dead vehicle.
After a jump start
Drive the vehicle for at least 30 minutes at a steady speed to allow the alternator to recharge the battery. If the battery goes flat again within a day or two, the battery is likely at the end of its life and needs replacing. Call Steins Garage on 0131 554 3423 for a battery check and replacement.