What to do if you have a flat battery

What to do if you have a flat battery
Even the most prepared drivers can take their cars for granted and end up with a flat battery. A dead battery can be caused by a number of reasons, with extreme weather, repeated short journeys or a fault with the vehicle all leading to excessive battery wear.

Whether you are at home or away, you might not realise your battery is going flat until it's too late. That's why it is important to understand the tell-tale signs of car battery problem. 

This guide gives you the know how to diagnose and fix a drained battery, and learn how to prevent your car from losing charge.

What to do if you have a flat battery

  1. Check that the battery is definitely the cause of a non-start using our tips
  2. Jump start the car yourself, or
  3. Call RAC Breakdown on 0330 159 1111, we’ll be happy to help even if you’re not a member

How to tell if you have a flat battery

Your car’s engine might not start for a number of reasons. To make sure the problem is definitely your battery, try checking the following:

  • Are the dashboard warning lights turning on?
  • Are interior lights and electric windows working?
  • Are there problems with central locking?

If you answered no to any of the above, your battery might be flat. However, there are a few things to remember:

  • Your battery might hold enough charge to turn on warning lights but struggle to turn on the engine. Dimly-lit icons are usually a big giveaway.
  • If your central locking is playing up, your key fob might be the problem. Try a spare set to help pinpoint the fault.
  • If you can’t turn the ignition key, your front tyre might be jammed against the kerb. Try turning your steering wheel away from the kerb, or rock the steering wheel from side to side as you turn the key.

Jump starting a car yourself 


If you want to jump start the car yourself you’ll need:

  • jump leads
  • a second vehicle with a well-charged battery
  • the confidence to take on the job

Our video guide on how to jump start a car explains everything you need to do in 10 simple steps.

What to do when calling the RAC

After you’ve given us a call on 0330 159 1111, there are a couple of important things you can do while you wait for us to arrive.

First, don’t attempt to start the engine or jump start your car yourself. You should also switch off any electrics in the car – such as radios, dash cams, chargers etc.

This will let our patrols test your battery correctly and help get your car up and running quickly.

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How RAC patrols will help with a flat battery

Our technicians will test your battery to see if it’s faulty and if it needs to be replaced. They’ll only recommend a new battery if it’s absolutely necessary.

We’ll fit a high-quality battery with up to 5 years warranty, and under our price match guarantee. 

If your existing battery is in good shape, we’ll jump start your car and have you back on the road in no time. 

How the RAC test your battery


Our patrols use advanced battery testers to check if: 

  • the condition of your battery is deteriorating and will need to be replaced soon
  • your battery has a fault and needs to be replaced straight away
  • your battery has run flat and needs a simple recharge

We can also see if there’s a problem with your car’s charging and starter system. Our state of the art battery tester can even highlight if a specific device in your car is draining the battery.

Technicians will talk you through the test results which can be printed on the roadside, whilst we're attending your breakdown at home, or sent to you by email.

When to replace a car battery

Batteries typically last for five years. However, this can vary depending on the quality of the battery and how your vehicle is used and maintained.

Frequent, short journeys prevent your battery from fully charging, eventually reducing charge capacity over time. Infrequent use of your car could also mean that your battery deteriorates faster.

If you can park your car in a garage, you’ll also protect your battery from the elements. Cold, flat batteries are one of the main reasons our patrols are called out during winter months. Car batteries can often be repaired, or in many cases, they are replaced. 

Common reasons that batteries go flat

We’ve already learned that batteries can go flat because of repeated short journeys, infrequent use and cold conditions – but there are plenty of other reasons why your battery might lose charge. 

Some common causes include:

  • leaving your lights on unnecessarily or mistakenly when parked
  • leaving dashcams and other devices plugged in
  • faults in batteries
  • faults in the charging system

If healthy batteries go repeatedly flat this can affect their ability to hold charge in the long term.

For advice on how to keep your battery healthy from home, discover the ways to make your car last longer

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Flat battery - FAQs

  • What do you do if your car battery goes flat?

    write blog content: What do you do if your car battery goes flat?
    If your car battery goes flat, the first step is to determine the cause of the flat battery. If the battery is simply drained because you left the lights on or it hasn’t been used in a while, you should be able to jumpstart the battery. If, however, the battery is dead and won’t charge, you’ll need to replace it.

    1. Make sure the battery is securely connected. Make sure the negative and positive cables are firmly attached to the battery terminals. If the battery is not securely connected, try reconnecting it.

    2. Jump start the battery. If the battery is simply drained, you can use jumper cables to jump start the battery. Make sure the jumper cables are properly connected to the dead battery and another vehicle with a good battery. Once the cables are connected, start the other vehicle and let it run for a few minutes. Try starting your car. If it starts, let it run for a few minutes to recharge the battery.

    3. Charge the battery. If the battery is still not working, you can try charging it by plugging it into the mains. You will need an extra peice of kit to do this. Make sure the charger is connected properly and that it is set to the correct volts and amps. Follow the instructions of the charger. Once charged, try starting the car.

    4. Replace the battery. If the battery still won’t start, it may be time to replace it.

  • Will a flat car battery recover?

    The answer is yes - it is possible to revive a flat car battery. However, it is important to understand the reasons behind the flat battery in the first place. If it is simply a case of the battery being drained due to leaving the lights on, then a jump start may be enough to get the battery back up and running. However, if the battery has failed due to a more serious issue, such as a faulty alternator or a short circuit, then a jump start might not be enough, and you may need to replace the battery altogether.

    If you are able to jump start the battery with a set of jumper cables, then it is important to note that it is still important to take the car to a mechanic for a check-up. This is because, although the battery may have been revived, there could still be underlying problems that need to be addressed.

  • How do you start a car with a flat battery?

    One option is to jump start the car. This requires another vehicle with a working battery and cables for connecting the two batteries. The cables should be connected to the positive and negative terminals of both batteries, and then the working vehicle should be started. Once it’s running, attempt to start your car. If it starts, leave it running for a few minutes and then disconnect the cables.

    If you don’t have access to another vehicle, you can also use a battery charger. This device can be plugged in to a power outlet and connected to the car’s battery. The charger will slowly recharge the battery and allow you to start the car. It’s important to make sure that the battery charger is compatible with the battery in your car.

  • Why is my car not starting but the battery isn't dead?

    If your car won’t start but the battery isn’t dead, it could be due to a variety of issues. The most common causes are a faulty starter motor, ignition switch, or a wider problem with the fuel system. There could also be an issue with the spark plugs.

    However, if your car won’t start but the battery isn’t dead, it is important to get it checked out by a professional mechanic as soon as possible. They will be able to diagnose the problem and recommend the necessary repairs to get your car back on the road.