How to Jump Start a Car: A Step-by-Step Guide
A flat car battery is one of the most common reasons a car refuses to start. If you turn the key or press the start button and hear a clicking sound, notice dim dashboard lights, or find that the engine will not turn over, your battery may have run out of charge.
Knowing how to jump start a car can help you get back on the road without waiting for roadside assistance. You can usually do this with a set of jump leads and a second vehicle with a compatible battery, or with a portable car battery jump starter.
In this guide, we explain how to jump start a car step by step, how to choose the right method, what to do after the engine starts, and how to avoid common mistakes.
Quick Answer: How Do You Jump Start a Car?
To jump start a car, you need a compatible power source, such as another vehicle or a portable jump starter. Before starting, make sure both vehicles are safely parked and switched off, and check that the flat battery is not damaged or frozen.
If you are using jump leads:
- Connect the red lead to the positive (+) terminal or designated positive jump point on the flat vehicle.
- Connect the other end of the red lead to the donor battery's positive (+) terminal.
- Connect the black lead to the donor battery's negative (−) terminal.
- Connect the other end of the black lead to the recommended earth point on the vehicle with the flat battery.
- Follow the vehicle handbook to start the donor vehicle, then try starting the vehicle with the flat battery.
- Once the engine starts, disconnect the leads in the specified reverse order.
Important: Always follow both vehicle manufacturers' instructions. Connection points and procedures vary between vehicles. Never jump start a cracked, leaking, swollen or frozen battery.
What Do You Need to Jump Start a Car?
Before you begin, prepare the equipment you need and make sure the method is suitable for your vehicle.
- Jump leads: Heavy-duty cables with insulated clamps that connect two compatible vehicle batteries.
- A donor vehicle: A second vehicle with a compatible electrical system and a suitable battery, if you are using jump leads.
- A portable car battery jump starter: An alternative that can start a compatible vehicle without requiring another car.
- Protective equipment: Safety glasses and suitable gloves can help reduce the risk of injury.
- Your vehicle handbook: This identifies the recommended jump-starting points and any model-specific precautions.
If you regularly drive long distances, travel in remote areas, or want to be prepared for unexpected battery problems, a portable jump starter can be a practical addition to your emergency kit.
How to Jump Start a Car with Jump Leads
Using jump leads is a common way to restart a car with a flat battery. However, incorrect connections can cause sparks, electrical damage or injury, so follow each step carefully.
Step 1: Park Both Vehicles Safely
Park the donor vehicle close enough for the cables to reach both batteries without stretching, but do not allow the vehicles to touch.
Switch off both engines and remove the keys or switch off the ignition. Apply the parking brakes and select Park for automatic transmissions or neutral for manual transmissions.
Turn off lights, heating, air conditioning and other electrical accessories. Check the vehicle handbooks for any additional precautions.
Do not attempt to jump start a battery that is cracked, leaking, swollen or frozen. If you notice damage or an unusual smell, stop and seek professional assistance.
Step 2: Identify the Battery Terminals
Locate the battery or the designated jump-starting terminals.
The positive terminal is usually marked with a plus sign (+), while the negative terminal is marked with a minus sign (−). Red covers commonly indicate positive terminals.
Some modern cars have batteries installed in the boot or beneath the seats, with designated jump-starting points under the bonnet. Use the manufacturer's recommended connection points rather than guessing.
Step 3: Connect the Red Jump Lead
Attach one red clamp to the positive (+) terminal or designated positive jump-starting point on the vehicle with the flat battery.
Connect the other red clamp to the positive (+) terminal or designated positive point on the donor vehicle.
Make sure both clamps are secure and do not touch each other or any metal parts.
Step 4: Connect the Black Jump Lead
Attach one black clamp to the negative (−) terminal of the donor battery, unless the vehicle manufacturer specifies a different connection point.
Connect the other black clamp to a designated earth point or suitable unpainted metal point on the vehicle with the flat battery, away from the battery and moving engine components.
Avoid connecting this final clamp directly to the negative terminal of the flat battery unless the manufacturer specifically instructs you to do so.
Step 5: Start the Donor Vehicle
Follow the donor vehicle manufacturer's instructions for jump starting. If permitted, start the donor vehicle and allow it to run briefly.
Do not rev the engine aggressively. If either vehicle displays a warning, the cables become hot, or you notice smoke or unusual smells, stop immediately if safe to do so.
Step 6: Start the Vehicle with the Flat Battery
Try starting the vehicle with the flat battery. If it does not start promptly, stop rather than repeatedly cranking the engine.
Allow a short pause before another attempt, following the vehicle and equipment instructions. If the engine still will not start, there may be a more serious battery, starter motor or electrical problem.
Step 7: Disconnect the Jump Leads
Once the engine starts and is running steadily, disconnect the leads in the order specified by the vehicle manufacturer. Where the standard reverse-order procedure applies:
- Remove the black clamp from the earth point on the vehicle that had the flat battery.
- Remove the black clamp from the donor battery.
- Remove the red clamp from the donor battery.
- Remove the red clamp from the previously flat battery.
Keep the clamps apart throughout the process and prevent them from contacting moving parts. Some vehicles have specific post-start instructions, so consult the handbook.
For more detailed instructions, read our guide on how to jump start a car with jump leads.
How to Jump Start a Car with a Portable Battery Pack
A portable car battery jump starter provides another way to start a vehicle with a flat battery. Unlike traditional jump leads, it stores its own power, so you do not need a second vehicle.
This can be especially useful when your car will not start at home, in a car park or somewhere without another vehicle nearby.
Step 1: Check the Jump Starter
Make sure the jump starter is sufficiently charged and suitable for your vehicle's battery voltage, engine type and starting requirements.
Check the manufacturer's instructions before connecting it. Never use a device that is damaged or has swollen batteries.
Step 2: Connect the Clamps
Switch off the vehicle and all electrical accessories.
Connect the red clamp to the positive (+) battery terminal or designated positive jump-starting point. Connect the black clamp to the recommended negative or earth point as specified by the jump starter and vehicle manufacturers.
If your jump starter has a smart clamp system, wait for the correct connection indicator before proceeding.
Step 3: Start the Engine
Follow the jump starter's instructions to activate the device, then attempt to start the vehicle.
If the engine does not start within the recommended cranking period, stop and allow the equipment to rest as directed. Do not continue making repeated attempts if the device indicates a fault or the connections appear incorrect.
Step 4: Disconnect the Jump Starter
Once the engine is running, switch off or deactivate the jump starter as instructed. Remove the clamps in the order specified by the manufacturer, keeping them away from one another and any moving engine components.
Store the jump starter safely and recharge it after use.
For more information, see our guide on how to jump start a car with a battery pack.
Can You Jump Start a Car Without Another Car?
Yes. If you do not have access to another vehicle, there are several options, depending on your situation.
Use a Portable Jump Starter
A portable jump starter is one of the most direct alternatives to a donor vehicle. It supplies the power needed to start a compatible car and can be kept in your boot for emergencies.
Choose a model that meets your vehicle's starting requirements and follow the supplied instructions.
Call Roadside Assistance
If you do not have suitable equipment, roadside assistance can assess the battery and help restart the vehicle. This is also the safer choice if you are unsure about the correct connection points or suspect an electrical fault.
Use a Battery Charger Where Appropriate
A compatible battery charger can recharge a flat battery, although charging is not the same as jump starting and may take considerably longer.
If the battery is deeply discharged, damaged or unable to hold a charge, it may need professional testing or replacement.
For more alternatives, read how to jump start a car without another car.
What Should You Do After Jump Starting a Car?
Getting the engine running is only the first step. You should also consider why the battery went flat and whether it needs further attention.
Allow the Battery to Recharge
Driving may help recharge a conventional 12-volt battery through the vehicle's charging system, but a short journey may not restore a deeply discharged battery.
Follow the manufacturer's advice about driving or charging after a jump start. If necessary, use a compatible battery charger to complete the recharge.
Check the Battery Condition
If the battery repeatedly goes flat, it may be ageing, damaged or unable to hold its charge. Other possible causes include a faulty alternator, a parasitic electrical drain or leaving accessories switched on.
Our guide to how to tell if a car battery is dead explains common warning signs.
Monitor Warning Lights
Pay attention to the dashboard after restarting. If the battery or charging-system warning light remains illuminated while the engine is running, have the charging system checked promptly.
If the engine stops again, the battery becomes hot or swollen, or you notice burning smells, stop driving when safe and seek professional help.
Common Reasons a Car Won't Start After a Jump Start
Sometimes a jump start does not solve the problem. Here are several possible explanations.
The Battery Is Too Damaged or Discharged
An old, damaged or deeply discharged battery may not accept enough charge to start the engine. A battery test can help determine whether it needs replacing.
The Connections Are Incorrect or Loose
Poor contact between the clamps and the approved connection points can prevent enough current from reaching the starter motor. Switch everything off and check the connections according to the instructions before trying again.
Never adjust live connections if doing so would risk short circuits or contact with moving components.
The Starter Motor Has a Fault
If the dashboard lights come on but the engine does not turn over, a faulty starter motor or related electrical component may be responsible.
The Charging System Is Not Working Properly
A faulty alternator or another charging-system problem can cause a battery to discharge again after the engine starts. Repeated jump starts will not fix the underlying issue.
If the car still refuses to start, arrange a professional inspection rather than continuing to attempt a restart.
How to Prevent Your Car Battery from Going Flat
A few simple habits can reduce the likelihood of being stranded with a flat battery.
- Avoid leaving electrical accessories on: Switch off lights and other equipment when the engine is not running, unless the vehicle is designed to manage them automatically.
- Check the battery regularly: Look for visible damage, corrosion or signs of deterioration.
- Take repeated short journeys into account: Short trips may not give the charging system enough time to replace the energy used to start the engine.
- Use a suitable battery charger when needed: If the vehicle is driven infrequently, a compatible maintenance charger may help keep the battery charged.
- Carry emergency equipment: A suitable portable jump starter can provide additional peace of mind.
- Investigate recurring problems: If your battery repeatedly goes flat, arrange a battery and charging-system test.
For further advice, read our guide on why your car battery keeps dying.
Frequently Asked Questions
How long does it take to jump start a car?
The actual starting process may take only a few minutes when the battery is suitable for jump starting and the connections are correct. However, troubleshooting, setting up the equipment and recharging the battery can take longer.
Can you jump start a completely flat car battery?
Sometimes. A discharged battery may recover enough to start the engine, but a deeply discharged, damaged or defective battery may not respond. Some smart jump starters also refuse to operate when they cannot detect a battery.
Follow the device instructions and never bypass its safety protections unless the manufacturer specifically provides an approved procedure.
How long should you leave a car running after a jump start?
There is no single time that applies to every vehicle. Driving may help recharge the battery, but a deeply discharged battery may require a proper charge using a compatible battery charger.
Follow your vehicle manufacturer's advice and have the battery tested if it repeatedly loses charge.
Is it safe to jump start a car in the rain?
Wet conditions increase the risks associated with roadside repairs. Follow the vehicle and equipment manufacturers' safety instructions, avoid standing water and do not handle damaged electrical equipment.
If conditions are unsafe or visibility is poor, contact roadside assistance rather than attempting a jump start.
Can jump starting damage a car?
Incorrect polarity, unsuitable equipment or connecting cables to the wrong points can damage vehicle electronics and batteries. Some vehicles require specific jump-starting procedures, so always consult the handbook before connecting equipment.
Never attempt to jump start a damaged or frozen battery.
Can you jump start an automatic car?
Yes, many automatic cars can be jump started using an approved external power source. However, push starting an automatic car is generally not appropriate and can cause damage.
Use the manufacturer's recommended jump-starting procedure.
Can you jump start a hybrid or electric car?
Some hybrids and electric vehicles have a separate 12-volt battery that can be supported using designated jump-starting points. However, the procedure and permitted equipment vary by model.
Never assume you can jump start the high-voltage traction battery. Follow the manufacturer's instructions or contact roadside assistance.
Should I replace my battery if it needs a jump start?
Not necessarily. A battery can go flat because the lights were left on or the vehicle was not driven enough to recharge it. However, repeated failures, poor battery-test results or an inability to hold a charge may indicate that replacement is necessary.
Have the battery and charging system checked if the problem recurs.
Be Prepared for the Next Flat Battery
A flat battery can happen at inconvenient times, but understanding how to jump start a car can make the situation easier to manage.
Whether you use traditional jump leads or a portable jump starter, the most important steps are to identify the correct connection points, follow the manufacturer's instructions and disconnect the equipment safely.
If you want an independent starting solution without relying on another vehicle, explore the GOOLOO Jump Starter collection to find an option suited to your vehicle.
A little preparation can help you deal with unexpected battery problems more confidently and get back on the road safely.
