As drivers, we are all likely to experience a flat battery at some point. Car batteries usually last around five years, and battery faults are the most common cause of breakdowns – so prevention is definitely better than cure.

Battery issues can occur at any time, but the problem is particularly acute in the winter, when cold temperatures affect the chemical process that produces and stores electricity. This slows the battery down and reduces its ability to hold a charge.

Although a flat battery can be jump-started or bump-started, older batteries have reduced performance, so there’s more chance you’ll wake up to a car that won’t start. Also, starting a car occasionally “isn’t likely to help,” says RAC spokesperson Simon Williams. “In fact, this may end up draining a weak battery.”

Read on for our guide to buying a new car battery, and your options for fitting it.

Why might my car battery be flat?

Although modern car batteries have features to help them preserve charge when left unused, the chemical reaction that occurs inside still discharges the battery slowly over time. Accessories such as car alarms and even the dashboard clock draw a small amount of charge, too. 

Alone, these should not cause a healthy battery to flatten fully, but they may be enough to drain the life out of an old or weakened one. This is especially true during the winter months.

Leaving interior lights on, or devices plugged into charging sockets, will obviously be a much quicker route to a dead battery. 

How can I stop my car battery from going flat?

The most obvious way to stop a battery going flat is to drive your car. Short trips won’t help, though. A 10-minute journey to the shops is unlikely to be sufficient to restore a battery’s charge.

Manufacturers such as Kia recommend allowing a little-used car engine to run at idle for 20 minutes once a fortnight. Doing so should allow the battery to remain charged up. For your own safety, this should be done outdoors, and with the car supervised at all times.

A dedicated battery charger, or a trickle charger, can also be used to maintain charge during extended periods when the car isn’t used. Some chargers also have the ability to ‘jump-start’ a flat battery. 

Where can I buy a new car battery online?

If all else has failed and your car battery is clearly in need of replacement, there are numerous options to order a new item online and have it delivered to your door.

Halfords offers a substantial range of new batteries, and the option to have them delivered. The company also offers a click-and-collect service, plus the option to spread the cost over a number of months.

Similarly, Euro Car Parts is able to supply various different car batteries with free delivery and click-and-collect options.

The RAC Shop sells an extensive range of batteries, and can have one delivered to your door the next working day. 

What kind of car battery do I need?

Unlike in many classic cars, you can no longer just stick any 12-volt battery under the bonnet and forget about it. Modern cars have complicated electrical systems, and the right battery is needed to avoid the risk of damaging them.

Cars with automatic start-stop systems, which can turn the engine off when stationary at traffic lights, need their own special type of battery. These will be marked as ‘AGM’ or ‘EFB’, and should be replaced with a similarly designated item. Car parts retailers such as those mentioned above all offer ‘battery finder’ tools on their websites.

Simply type in your car registration number to find the best match for your vehicle. And also check against what is currently fitted, just to be sure.

Can I fit a new car battery myself?

Again, the complexity of modern cars means fitting a new battery yourself is not necessarily a simple task. Cars with automatic start-stop need to have their battery management system reset when a replacement is fitted, which requires specific equipment to do. 

For those with older vehicles, the RAC offers a comprehensive guide, should you feel confident enough to replace a battery yourself. If you are unsure about fitting a battery yourself, leave it to a professional.

What if I want someone to fit it for me?

If you decide to have a new battery fitted by someone else, you have multiple choices depending on your circumstances. 

Should your battery be completely flat, and you have breakdown cover, check if your policy includes battery replacement. Both the RAC and AA either offer free (or low-cost) battery fitting for members. Certain policies include the actual cost of the battery, too. 

Non-members can also use the RAC and AA to supply and fit replacement batteries, with same-day services advertised. Halfords offers mobile battery fitting as well.

Should your car still be drivable, but with a battery that will need replacing, various retailers can fit a replacement for you in store. 

Halfords, Euro Car Parts, Kwik Fit and ATS Euromaster are all able to offer battery fitting services. It should be a relatively quick, while-you-wait process – certainly less than an hour.

What if I own an electric or hybrid car?

Electric and hybrid vehicles typically feature two distinct batteries: a main lithium-ion unit for the electric motors, plus a regular 12-volt battery for accessories such as lights and heated seats.

This 12-volt unit can run out of charge, just as in a petrol- or diesel-engined car. If this battery is flat, it may prevent an electric car from starting, regardless of how full the main battery is.

Cleverly, some plug-in vehicles, such as the Kia Niro, are able to jump start the 12-volt battery from their main lithium-ion battery.

Charging and replacing the 12-volt battery in an electric or hybrid vehicle is likely to be more complicated than for a conventional car. Read the handbook for your specific car to avoid the risk of damaging electrical components.

ALSO READ:

How to charge a car battery

Winter is coming: how to prepare your car for the cold

Your EV questions answered on Motoring Electric