A flat battery is one of the most common reasons a car won’t start. Whether you’ve left your lights on overnight, your battery is old, or cold weather has affected performance, knowing how to jump-start a car can help you get back on the road quickly and safely.
In this guide, we’ll explain how to jump-start a car with jump leads, how to jump-start a car without jump leads, important safety precautions, and what to do afterwards to avoid further battery problems.
What does jump-starting a car mean?
Jump-starting a car means using an external power source to temporarily supply enough power to a flat battery to start the engine. This is usually done using jump leads connected to another vehicle with a working battery, although portable battery boosters can also be used. Once the engine starts, the alternator should begin recharging the battery while the car is running.
A flat battery can happen for several reasons, including:
Leaving lights or electronics on.
Cold weather is reducing battery performance.
An ageing battery.
Faulty electrical systems.
Long periods without driving.
If battery problems happen regularly, you may need to learn how to check your car battery's health.
How to jump-start a car with jump leads
What are jump leads and how do they work?
Jump leads are insulated cables designed to transfer power from one vehicle’s battery to another. They usually come with colour-coded clamps:
Red = positive (+)
Black = negative (-)
The leads allow electricity from the working battery to flow into the flat battery, providing enough power to start the engine. Understanding how to use jump leads correctly is important, as incorrect connections can damage the battery or electrical systems.
Before you start: What do I need?
Before jump-starting a dead battery, you’ll need:
A set of jump leads.
Another vehicle with a working battery.
Access to both batteries.
Gloves and protective eyewear, if available.
Make sure both vehicles are parked safely with engines switched off and handbrakes applied.
Before you start: Safety precautions
Before learning how to jump start a car with jump leads, follow these important safety checks:
Never smoke near a battery.
Keep metal objects away from battery terminals.
Check for cracks, leaks, or visible battery damage.
Make sure the leads are not damaged.
Ensure the vehicles are not touching.
Switch off lights, radios, and air conditioning in both vehicles.
If the battery appears swollen, leaking, or damaged, do not attempt to jump-start the vehicle.
Cold temperatures can often contribute to battery failure, especially during cold weather.
How to use jump leads
Using jump leads correctly is essential for safety and to prevent damage to the electrical system.
The connection order matters:
Connect the red clamp to the positive terminal on the flat battery.
Connect the other red clamp to the positive terminal on the working battery.
Connect the black clamp to the negative terminal on the working battery.
Connect the final black clamp to an unpainted metal surface on the car with the flat battery.
Avoid connecting the final black clamp directly to the dead battery unless the vehicle handbook specifically advises it.
Step-by-step: Jump-starting a car with jump leads
Follow these steps carefully:
Step 1: Position the vehicles
Park the working vehicle close enough for the jump leads to reach, but ensure the cars are not touching.
Step 2: Turn both engines off
Remove the keys and apply both handbrakes.
Step 3: Connect the jump leads
Attach the leads in the correct order listed above.
Step 4: Start the working car
Allow the engine to run for a few minutes to transfer charge.
Step 5: Try starting the flat car
Attempt to start the vehicle with the dead battery. If it doesn’t start immediately, wait another few minutes before trying again.
Step 6: Let both engines run
Once started, leave both engines running for several minutes. Many drivers wonder how long it takes to jump-start a car. In most cases, leaving the engine running for at least 15-30 minutes will help recharge the battery enough for short-term use.
How to remove jump leads
Disconnect the leads in reverse order:
Remove the black clamp from the previously flat car.
Remove the black clamp from the working battery.
Remove the red clamp from the working battery.
Remove the red clamp from the restarted car.
Take care not to let the clamps touch each other during removal.
How to jump-start a car without jump leads
If you don’t have jump leads available, there are still a few options depending on the vehicle and situation.
Before you start: What do I need?
You may need:
A portable jump starter pack.
Another person to help.
Safe access to the vehicle.
Portable jump starters are often the easiest and safest alternative to traditional jump leads.
Before you start: Safety precautions
The same safety rules apply:
Check the battery for damage.
Avoid sparks or open flames.
Follow the instructions provided with your jump starter.
Keep the vehicle in a safe location away from traffic.
Step-by-step
Using a portable jump starter
Connect the positive clamp to the battery’s positive terminal.
Connect the negative clamp to a metal grounding point.
Switch on the jump starter.
Attempt to start the car.
Disconnect the device once the engine is running.
Push starting (manual cars only)
If you drive a manual vehicle, push starting may work in some cases:
Turn the ignition on.
Press the clutch and select second gear.
Have helpers push the vehicle.
Release the clutch once moving.
The engine may start as the wheels engage.
This method should only be used when safe and practical.
What to do after you’ve jump-started your car
Once your vehicle is running again, avoid switching the engine off immediately. Drive continuously for 20-30 minutes to fully recharge the battery.
If the battery keeps going flat, there may be a larger issue, such as:
An old battery.
Alternator problems.
Loose wiring.
Electrical faults.
Regular maintenance can help prevent breakdowns, especially during seasonal weather changes, such as in autumn or summer. Different conditions and temperatures will affect the overall health of the car.
Frequently asked questions regarding jump-starting a car
How often should you change your car battery?
Most car batteries last between three and five years, although this depends on driving habits, weather conditions, and maintenance.
Can you drive your car after a jump start?
Yes. In fact, driving the vehicle helps recharge the battery. Aim to drive for at least 20-30 minutes after jump-starting.
Is it possible for a car battery to be too dead to jump start?
Yes. If the battery is severely damaged, extremely old, or unable to hold a charge, jump-starting may not work, and the battery may need to be replaced.
Is jump-starting a car dangerous?
Jump-starting a car is generally safe when done correctly. However, improper use of jump leads can cause sparks, damage batteries, or cause electrical issues.
Does jump-starting a car damage the battery?
Occasional jump starts should not damage a healthy battery. However, repeated jump-starts may indicate an underlying problem that needs investigation.
Can automatic cars be push-started?
No. Most automatic vehicles cannot be push-started because of the way their transmissions work.
Why does my car battery keep going flat?
Frequent flat batteries can be caused by an ageing battery, electrical drain, a faulty alternator, or cold weather conditions.
