How to jump-start a car: Using and removing jump leads
There’s never a good time or place for your car battery to go dead, especially when you’re already way behind schedule for the day. But, with the help of another vehicle, some jumper cables and the right know-how, you can revive your car battery — at least long enough to get you to the garage to replace it!
To ensure you are prepared for the unexpected, we have put together this useful guide on how to jump-start a car. Here, we will walk you through the stages of how to jump-start a car with leads, as well as including an FAQ section to answer commonly asked questions.We'll cover:
- What you'll need
- Performing a safety check
- How to jump-start a car with leads
- Removing the jump leads
- Jump-start FAQs
- Jump leads — these need to be clean and in perfect condition with no frayed wires or rust. If you are in need of replacing yours, we have a great selection of jump leads and booster cables with varied lengths and amps so you’re sure to find the right one to jump-start your vehicle. You should check the current characteristics, such as battery capacity and voltage and the starting current on your battery plate to find compatible ones.
- Rubber work gloves
- Safety goggles — be sure to check that these have been certified for auto repair.
- A vehicle with a fully charged battery that has a matching voltage to yours.
Before you jump-start your car battery, it’s important to assess that there is nothing physically wrong with the battery first and that it has just gone dead. You will also need to be aware of your surroundings as certain things can make your car battery explode or cause serious damage.
To ensure you are safe before, during and after jumpstarting your car with leads, follow these do’s and don’ts:
- Check that the voltage of the vehicle being jumped matches that of the vehicle it is connected to. If these don’t match up, it can cause serious damage to both of the cars.
- Make sure the engine is off in both of the cars.
- Unplug all accessories before jumpstarting, as the power can short their circuits out.
- Make sure all electrical elements, including any bulbs, are switched off in both vehicles.
- Ensure the cars are both parked close enough for the cables to reach, but not close enough to be touching. Both vehicles need to be parked with the handbrake on.
- Take precautions by wearing safety goggles and rubber gloves before jumpstarting.
- Attempt to jump-start the car if your battery is damaged or leaking as this can cause an explosion.
- Lean over the battery of either car in case it sparks or explodes.
- Jump-start a battery if any of the fluids are frozen as this can cause an explosion.
- Smoke while jumpstarting a car as this can cause fire.
- Wear rings or metal jewellery or let anything metal touch the battery terminals.
Here, we will be taking you through the process to ensure you are going about the procedure safely and responsibly.
- Firstly, you’ll need to ensure the cars are parked close enough together without them being able to touch. It will be easiest to position the cars so the bonnets are facing each other as this will mean your jump-start cables won’t need to stretch over cars. Both of the cars should have all of their electrical equipment and ignition switched off and be parked with the handbrake securely on.
- Open the bonnet of both cars and attach one end of the red jump lead to the positive terminal of the flat battery. These terminals will usually be protected by a plastic film so be sure to peel this back before attaching the jump lead. It’s important that you connect the jump lead to the dead battery first as it will have less power than the good battery, so there is less chance of shock or explosion.
- Take the other end of the red jump lead and attach it to the positive terminal of the vehicle with a fully charged battery, again making sure to peel back the plastic film before putting these together.
- Repeat with the black jump lead, connecting it to the negative terminal of the charged battery. You can then attach the other side of the black jump lead to a productive earth point in the car with the dead battery — this means picking a place which will have a direct physical connection to the earth. Ideally, this will be a solid metal part of the engine as this will be a good conductor to encourage and carry the current between vehicles.
- Once both cars are all hooked up, wait for around 3 minutes and then start the engine of the car that’s got a fully charged battery.
- You can now also start the battery of the car with the dead battery. If your car’s ignition starts up as normal when you turn the key, the jump-start has worked.
- You should drive the car for at least 30 minutes after to allow the alternator to recharge the battery. Now that you have jumpstarted your car battery, the vehicle’s engine should be running properly after this, but if it is still struggling to start, there may be a deeper issue at hand. If so, you will need to call for breakdown assistance and get your car seen to by a professional.
No matter how short the journey you’re taking, make sure that you’re prepared for unexpected incidents. We recommend having travel essentials, including emergency items and a first aid box stored in your car at all times to keep you safe and comfortable while you wait for recovery.
There is no golden rule for when to remove the jump leads once your car is up and running — this can be anything from straight away after you’ve accumulated power to around 10 minutes after your battery has showed its first signs of being powered up. The longer you leave it connected, the more charge it will gather. However, there are some rules you will need to follow to ensure you disconnect your jump leads safely and responsibly:
- Turn off the engines of both vehicles before disconnecting the jump-start cable. This is particularly important as the electrical current could cause electric shocks and damage the car’s important electronics. This can prevent the vehicle’s sensors, comfort systems and ignition from working.
- You will then need to remove the black lead from the negative terminal of the car that needed powering fist, and then from the booster car. Once you’ve done this, repeat for the red lead, ensuring you disconnect it from the jump-started car first and then the booster one.
- Make sure that none of the leads touch one another or the car when you’re removing them as this can cause sparks and explosions if they are still carrying the electric current.
- Turn the jump-started car’s engine back on once all wires have been removed safely. If your car now fails to restart, you will need to seek professional help as this could signify a problem with your battery or engine.
If you would like to see any of these steps in detail, be sure to check out ChrisFix’s YouTube tutorial on how to properly jump start a car. Here, he shares his best tips for hooking the cars up, disconnecting the jump leads and finding a good and safe Earth point.
Q: Can you jump-start your car without another car?
A: Yes. Although jump-starting your vehicle with another one can be the simplest way to get your car back up and running, there are some ways you can start your car if the battery fails without another vehicle.
One method is to push start your car. This requires at least two people and can be started by putting the clutch down and placing your car in second gear. You should next turn on your ignition without starting the car and gently release the brakes. Once the car begins rolling at a speed of approximately 5 mph, you can release the clutch. As the car builds momentum, continue driving to charge the battery.
Another way to get a jump-start is to hook your cables up to a fully charged back-up battery. You can do this in the same way as we have described in the previous section on jump-starting a car with leads. It's also important to remove jump leads from the jump-started car before you remove them from the spare battery to reduce the chances of sparks or electrocution.
Q: Can you jump-start an automatic car?
A: Yes. An automatic can be jumpstarted the same way as described in the ‘how to jump-start a car with leads’ section. But, unlike a manual transmission that can be pushed to start when there are no jump leads available, an automatic vehicle cannot be push started as this will damage the transmission.
Q: Can you jump-start a car in the rain?
A: Yes. The electrical system inside of cars will not have a high enough voltage to cause you any harm or risk of electrocution, so there is no danger from doing this. Just make sure that you carefully dry your jump-start leads before storing them away so that they do not accumulate rust or become damaged.
Q: Can you jump-start a car in reverse?
A: Yes. Sometimes the only option will be to jump-start your car in reverse, so the same method can be used as described above. It’s important to remember reverse is a low ratio gear, meaning push starting it can damage the transmission and clutch. Additionally, you may experience more of a sudden jolt when releasing the clutch, but this is normal.
Q: Can you jump-start a petrol car with a diesel?
A: Yes. Despite this not being recommend traditionally, it is generally fine for a petrol car to be jump-started from the battery of a diesel one. The main thing to check for before doing this is that the two battery voltages are the same to remove any risk of burning out the starter motor or causing an explosion. If you are still concerned about this, we recommend getting a professional to help.
Q: Can you jump-start a diesel car with a petrol car?
A: Yes. Contrary to popular belief, this is perfectly fine. However, you will need to ensure that the two battery voltages are the same to remove any risk of burning any of the crucial engine parts or causing an explosion.
Battery after care
Even if your battery has started, the power surge it received from the jump-start won’t usually be enough to fully charge it from dead, so we advise investing in a good car battery charger that will power it to its full capacity.
Here at GSF Car Parts, we have a great selection of battery chargers, so you’re sure to find one that is compatible with your vehicle. If you don’t already know which one you’ll need, simply enter your car registration and details in the box provided at the top of each page and we will be able to find the correct battery charger for your car.
Typically, car batteries last between 3-4 years, but this can differ depending on how often you drive, the quality of your driving and weather conditions, so make sure you are taking care on the road with gear changes and speed. We have a guide to car batteries that includes plenty of helpful information on how to check, choose and change your car battery which will help you work out whether jumpstarting can revive your dead car battery or if there is another issue at hand.
Hopefully this guide has made you confident with the jump-starting process so you can get back on the road quickly and safely.
Here, at GSF Car Parts, we have all of the main equipment you’ll need to jump-start your car battery, as well as battery maintenance products to ensure your car’s engine is running smoothly.
For more help and advice about your vehicle and any problems, be sure to check out our blog and our knowledge hub. If you’re looking for more information about any of our products, please don’t hesitate to contact us for more information. We offer free UK delivery, as well as a free Click and Collect service from over 70 of our branches, so you can get your necessary car parts in no time.