If there is one component that your car relies on more than any other it’s the battery. Without a functioning car battery, you will have no lights, no sound system, no heating and most importantly no way of starting the engine. Yet battery trouble is the number one reason breakdown companies and garages are called out to faulty cars.

And because batteries have a limited operating life, a fifth of the country’s cars need to have their battery replaced every year. That’s around five million faltering batteries. Here’s how to look after one of your car’s most important components.

How do you know if a car battery is about to die?

A red battery-shaped light should come on in your car’s instrument panel when the ignition is turned on. This is the car checking that the battery is in working order. If all is well with it, the warning light will go out. Sometimes you can tell that the battery is coming to the end of its life because it can’t supply enough current to turn the engine over as vigorously as is needed. On other occasions, particularly after a cold winter’s night, it won’t give the starter motor enough beans to turn the engine over at all.

What if the battery light comes on while you’re driving?

This indicates a fault with the car’s charging system. What it usually means is that the alternator, or the link between that and the engine, has failed. You will be able to continue driving for as long as the battery can survive without being charged. A garage should be able to diagnose exactly where the fault lies. What you shouldn’t do is immediately assume your battery is dead and replace it. If the problem lies with the charging system, a new battery will run down almost as quickly as the old one.

What the car battery does

A battery leads a hard life and powering a starter motor to turn an engine over is an exhausting business. Once it’s done that and you’re on your way without a second thought, the battery is gasping a sigh of relief. It’s just done its equivalent of a sub 10-second sprint and is attempting to get its breath back. The trouble is, modern cars are very energy hungry. So as well as recovering from starting the engine, the battery will be powering the lights, electric windows, wipers, heating and maybe even an in-car touchscreen. All this requires current. And unless you plug into an external power source, the only way the battery has sufficient charge to supply the current is through the car being driven.

How to keep your battery fit

Not giving a battery much charge after starting the engine, is like asking a runner to do another race without having a rest or any food. And if a battery is kept at less than 80% of its charge, the acid in the cells starts to gather at the bottom. This process is called acid stratification and it prevents the battery holding its charge. To stop this and keep the battery in tip top shape, try to drive for at least 20 minutes once a week.

Show it some respect

By necessity, batteries need to be hard wearing: they should live between five and seven years. You can have an impact on that by giving your battery some TLC. Before you’ve got the engine running, don’t turn the headlights on or whack the ventilation fan up to max. That way the battery will be able to concentrate all its energy on cranking the engine. This is especially important in the winter. Engine oil is thicker in cold weather and it requires more energy from the battery to turn an engine sufficiently for it to fire up.

How to check your battery?

It’s very difficult to know how much life your battery has left in it without specialist equipment. That’s where your garage comes in. Many will check batteries for free.

Mechanic in high vis gloves testing car battery with yellow machine

Professionals have special battery testing kit to tell you how healthy yours is

What kind of battery do you need?

An increasing number of cars are fitted with stop/start technology which cuts the engine when the car is stationary and automatically re-starts it when you want to drive off. This improves fuel consumption but requires an even more durable battery. These are known as Absorbed Glass Mat (AGM) and they deliver more power more quickly than regular lead-acid batteries. The downside is they’re more expensive than traditional batteries. And a professional may have to reset the car’s battery management system after an AGM battery has been replaced.

What about charging batteries?

If you don’t use your car a great deal, one way to prevent the battery degrading is to use a charger. Modern smart chargers constantly monitor the battery’s state of charge and provide sufficient power to keep it in tip-top shape. However, some car makers recommend that you don’t charge their battery and that you use a professional to fit a new one.

Find the nearest garage to check or fit a new battery