How to Jump Start a Car Safely

A flat battery is one of the most common reasons a car won't start, and jump starting it yourself is usually straightforward if you follow the right order.

What you need

• A working vehicle with a charged battery, or a portable jump starter pack
• A set of jumper cables (if using another car)
• Both vehicles parked close enough that the cables reach, but not touching

Step by step

1. Turn off both vehicles and remove the keys.
2. Connect the red (positive) clamp to the positive terminal on the flat battery.
3. Connect the other red clamp to the positive terminal on the working battery.
4. Connect the black (negative) clamp to the negative terminal on the working battery.
5. Connect the final black clamp to an unpainted metal surface on the car with the flat battery, such as the engine block, not the battery itself. This reduces the risk of sparks near the battery.
6. Start the working vehicle and let it run for a few minutes.
7. Try starting the vehicle with the flat battery. If it starts, let it run for at least 15 to 20 minutes to build some charge back up.
8. Remove the cables in the reverse order you connected them.

If it still won't start

If the engine cranks but won't fire, or nothing happens at all, the issue might not be the battery. It could be the alternator, the starter motor, or a deeper electrical fault. Jump starting only works if the battery itself is the problem.

When to see a mechanic

If your battery keeps going flat even after a jump start, it's worth getting it properly tested rather than jump starting it every few days. A weak battery or a failing alternator can leave you stranded at a worse time. You can compare local mechanics and request a quote on Spott to get it checked properly.