How to Jump Start a Car Safely: Step-by-Step Guide

What you need to jump start a car

You need a set of jump leads (jumper cables) in good condition and a second car with a healthy 12 V battery, or a charged portable booster pack. The leads should be thick, with undamaged insulation and clamps that grip firmly. Thin leads get hot and often fail to turn a large engine such as a V8 SUV.

Keep the handbook nearby. On many modern cars the battery sits in the boot or under a seat, and the handbook shows dedicated jump points under the bonnet: a positive post under a red cap and an earth stud.

Safety checks before you connect anything

Do not jump start a battery that is cracked, leaking, swollen or smells of rotten eggs. A damaged battery can vent gas or acid when a heavy current hits it, and after a Dubai summer a swollen case is not unusual. That battery needs replacing, not jump starting.

• Both cars must have 12 V systems. Never use a 24 V truck to start a car.
• Switch off both ignitions, the lights, the AC and the radio. Unplug phone chargers.
• Keep jewellery, loose sleeves and the leads away from fans and belts.
• No smoking and no naked flames near either battery.

The correct jump lead order, step by step

The correct order is red to the flat battery, red to the donor, black to the donor, then black to bare metal on the car with the flat battery. Removal is the exact reverse.

1. Check both batteries and the leads. Stop if the flat battery is damaged, leaking or swollen.
2. Park the cars close but not touching, handbrakes on, ignitions and all electrics off.
3. Clamp one red end to the positive (+) terminal of the flat battery.
4. Clamp the other red end to the positive (+) terminal of the donor battery.
5. Clamp one black end to the negative (-) terminal of the donor battery.
6. Clamp the last black end to bare, unpainted metal on the car with the flat battery, such as an engine bracket or the earth stud shown in the handbook, well away from the battery.
7. Start the donor car and let it run for a few minutes, typically 3 to 5. Then try the other car, cranking for no more than about 10 seconds at a time with a minute between attempts.
8. Once it starts, let both engines idle for a few minutes. Then remove the leads in reverse: black from the earth point, black from the donor, red from the donor, red from the jump-started car.
9. Keep the engine running, drive for at least 30 minutes if you can, and have the battery tested.

How long to leave the engine running afterwards

Keep the engine running for at least 30 minutes after a jump start, and drive the car if you can, since idling charges slowly. An alternator is built to keep a healthy battery topped up, not to refill one that has gone flat. A deeply discharged battery typically needs several hours on a proper charger to recover fully.

A short drive around JBR will not do it. A slow crawl beside The Walk or a move from one basement to another, with the AC on full and the lights on, puts very little back into the battery. Switch off at the next stop and the car may not restart. A steady run on Sheikh Zayed Road does far more.

Using a portable booster pack instead of a second car

A portable booster pack replaces the donor car and is usually the easier option in a tight parking bay. Check that it is a 12 V unit rated for your engine size and that it is well charged before you rely on it.

1. Switch off the ignition and all electrics.
2. Clamp red to the positive (+) terminal or jump post.
3. Clamp black to the earth point, or to the negative terminal if the booster's instructions say so.
4. Switch the booster on, wait a moment, then start the engine.
5. Switch the booster off and remove black first, then red.

Lithium boosters weaken in heat, so check the charge on one that has spent the summer in the boot.

What not to do when jump starting

The mistakes that cause real damage are reversed polarity, clamps touching and using the wrong donor car.

• Do not reverse the leads. Red goes to positive (+) only. Reversed polarity can blow main fuses and damage the alternator and control units.
• Do not let the clamps touch each other, or let a red clamp touch the bodywork once the other end is connected.
• Do not use a hybrid or electric car as the donor unless its handbook allows it. Its 12 V system is fed by a small converter that is not built to supply another car's starter.
• Do not touch the orange high-voltage cables on a hybrid or EV. If its own 12 V battery is flat, use only the 12 V jump points shown in its handbook.
• Do not keep cranking. If the engine has not started after three or four short attempts, stop.

What it means if the car dies again

If the car dies again, either the battery is no longer holding charge or the charging system is not charging it. Which one depends on when it happens.

Call a technician if the battery looks damaged, if you have no leads or cannot get a second car close, if the car is a hybrid or EV and the handbook is unclear, or if it has needed a second jump in the same week. In JBR a technician can test the battery where the car is parked, jump start it or fit a new one on the spot, 24/7. New batteries carry a warranty of up to 24 months.