How we'll fix your flat car battery

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What should you do if you have a flat battery?

If your car won't start, there's a good chance the battery's gone flat. A flat battery is one of the top 10 breakdown causesHere's how to tell if you have a flat battery and what to do:

1. Double check that it's a flat battery
  • Make sure there's fuel in the tank.
  • If the central locking isn't working, your key fob might have died so try a spare key.
  • If you can't turn the ignition, check the wheels aren't jammed against the kerb.
  • Check your dashboard warning lights. If the dash lights are flickering or don't come on, it's likely the battery is discharged.
2. If you think it's likely a flat battery, try jump-starting your car.
3. If you can't jump start your car, get in touch so we can charge or replace your car battery.
  • If you're already a member, we're available to help with breakdown cover. But, even if you're not a member yet we can still help out. Just call us on 03330 046 046.

We provide 24/7 roadside assistance.

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What we can do to help

If you've got a flat battery, we won’t just jump-start you and send you on your way. As well as charging or replacing your battery, we'll try to find out why it went flat in the first place.

If we can't see why the battery died or we think it's faulty, we'll carry out a battery test. Our test is very thorough and we'll only ever recommend a new car battery if you really need one.

Once we reach you, we'll:

  • Test your car battery
  • Look at your car's charging system
  • Check for a fault that could've drained your battery
  • Partially charge your battery or replace it, if required, so you can continue your journey.

Find out more about our specialist battery testers and instant breakdown cover if you've broken down.

Testing your car battery’s health

We get an immediate digital report of your battery readings so we can check the condition of the battery.

The different readings can be:

1. Good battery:
  • The fault's not with the battery.
  • We’ll check your car’s charging system and find out why it broke down.

2. A bad cell:
  • Car batteries contain several 2.1 volt batteries known as cells.
  • If one's not working, the battery will need to be replaced.

3. Replace battery:
  • This reading is clear - the battery’s just not up to it anymore.

4. Needs charging:
  • This means that your battery's working, but it needs a full recharge.
  • We’ll check your charging system to find out of what drained it.
  • Next, we'll give you a jump start to get the engine going.
  • Before you go, we'll advise how to fully recharge the battery.

5. Consider replacement:
  • Your car battery passed the test - but only just.
  • This means the battery's coming to the end of its life.
  • We'll advise how soon you should change the battery based on how you use your vehicle.

Flat battery vs dead battery

If your battery has stopped working, it may just be flat and in need of recharging. However, it's possible for a car battery to sustain so much damage that it won't work again, this is when it's considered a 'dead battery'.

The longer you leave a flat battery alone without recharging it, the more likely it is to become a dead battery.

Flat battery test

When to replace a car battery

There's no hard rule about how long car batteries should last or when they should be replaced.

Most batteries will last somewhere between 5 and 7 years. However, our mechanics see cases where the battery has failed after only 2 or 3 years because of how the car was driven.

As a rough rule of thumb:

If the engine struggles to start before the battery is 5 years old, it probably means:

  • The battery isn't getting enough charge.
  • The car's doing too many short journeys, or
  • There's a vehicle fault draining the battery or affecting charging.

Starting problems after 5 years are more likely to mean:

  • The battery's getting tired and may need replacing.

What to do when your car battery dies

First of all, make sure that your battery is actually dead, rather than just flat. If it's just gone flat, you may be able to jump start it by using jump cables and another vehicle with a working battery.

See our guide on how to jump start a car for a more in-depth walkthrough. If jump starting your car doesn't work, you'll need a new battery.

Find out how breakdown cover can help you if you have car trouble:

Dead battery? We'll replace it the same day with Battery Assist.

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Why do car batteries go flat?

If you're wondering 'what drains a car battery?', most car batteries fail because they don’t get the chance to recharge properly.

You can halve the battery's lifetime by not fully charging it regularly. This costs you money and risks your car having a breakdown.

There are all sorts of reasons for a dead battery, but the most common are:

  • The car hasn't been used for a while
  • The car's only used for short or stop-start journeys
  • The lights were left on
  • There's a faulty component
  • There's a problem with the car’s charging system
  • You've got a fault with the battery itself

Batteries can fail for other reasons, like too much vibration from the engine, over-charging, corrosion and extreme temperatures. Flat batteries are the most common reason why cars won't start in winter.

Plus, modern cars have lots more power-hungry electronics than older cars used to. Think of built-in sat navs, infotainment systems, seat heaters and USB plugs. All of them put strain on the battery.

How long does a car battery last?

A car battery could typically last anywhere from 3-6 years, largely because differences in driving habits and frequency of use can cause batteries to age at different rates. The more care you take of your car overall, the bigger the lifespan you can expect from your car battery.

Why do car batteries go flat in cold weather?

The cold weather can affect cars by slowing down their internal processes. The chemical reaction that happens inside your car battery when you start up the engine is one of those processes. With severe enough temperatures your car battery will have a reduced capability to hold a charge.

Can a car battery go flat by sitting around?

It's possible for a car battery to go flat if the car is left unused for long enough. However, it's much more likely to happen with an older car or a car that hasn't been maintained properly. Keep your car in good shape by following our maintenance tips.

Why is my car battery not charging?

Problems with the alternator are sometimes the cause of a car battery not charging, though it can also be due to the battery cables or battery terminals becoming corroded.

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How to keep your car battery healthy

There are a few ways you can avoid getting a flat battery and help your car's battery last longer:

1. Go for regular drives
  • 30 minutes or more will help the battery recharge.

2. Invest in an intelligent charger
  • If you don't use the car much, you can leave these connected for long periods without damaging the battery.

3. Try a solar charger
  • It won't charge a flat battery, but it'll help to keep the battery charged on a vehicle you don't use much.

4. Switch all electrics off
  • Make sure all electricals like heaters, windscreen wipers and stereo are off when you park or start the car.

5. Dip the clutch
  • Dip the clutch when you start the car to take some load off the starter motor and the battery.

Flat battery help with Battery Assist

Our Battery Assist service will help you whether you're a Member or not. And you can also call us out even if it's not an emergency breakdown.

If your battery goes flat, we'll charge it or replace it so you can carry on your journey.

Will a flat car battery recover?

If your car battery is flat and your car is less than three years old, then there's a decent chance you'll be able to revive your battery with a jump start or simple recharge. This is also the case if you accidentally left an interior light on in your car and the battery was drained because of it.

Can you charge a car battery?

Yes, if your car battery has gone flat (rather than completely dead) you'll be able to recharge it with a battery charger. You can buy a car battery charger online, but make sure you get the right type for your car. If you have an EFB or AGM battery type, then you'll need to get a smart charger.

Can a dead car battery come back to life?

If a car battery is dead the bottom line is that it will need to be replaced sooner rather than later. However, you may be able to temporarily revive the battery with a jump start, just to get you where you need to go. This is a temporary measure and you should take your car to a garage as soon as possible.

Flat batteries on electric vehicles

Electric vehicles inherently rely on batteries to keep them moving. It's unlikely for an electric vehicle's high voltage battery to go flat, as long as you keep them charged enough. Electric car batteries will typically outlive the vehicle that they're placed in, though they can degrade over time and therefore their charge capacity becomes lower.

This means you won't be able to drive for as long on a full charge once you've owned an electric car for several years. The 12 volt battery on an electric vehicle can be just as problematic as a conventional vehicle.

Other reasons your car won't start

Flat batteries are one of the most common issues, but there are other reasons your car might not start. Starter motor problems, fuel problems, engine problems, faulty immobilisers and alternator problems could all contribute to a major fault with your vehicle. If your car won't start, you can always contact us for help. Get breakdown cover or call us on 03330 046 046 for same-day assistance if you're not already a member.

*Source: 313,162 AA Attended Breakdowns for batteries, January 2018 – December 2018

Published: 7 April 2016 | Updated: 11 January 2024 | Author: The AA

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