How to change a car battery and choose the right battery for your car

If your car is struggling to start, a bit dimly lit or well and truly dead, there's a good chance that you’ll need to change your car’s 12V battery. 

While you could pay someone to source a new car battery and fit it for you, buying a new battery and fitting it yourself could save you quite a lot of money - as well as meaning one less trip to the garage. The best news is that changing a car battery is a straightforward job in most cases, and all you’ll need are some basic hand tools and a little bit of confidence.

So how do you change a car battery and choose the right battery for your car? Our guide is here to explain everything you need to know.

What are the symptoms of a dead car battery?

If your car’s 12V battery is dead, this will quickly become obvious as your car will fail to start, and the on-board electronics may also refuse to work. Obviously, a car that won’t start is a huge inconvenience, so looking out for the symptoms that can occur before the battery fails can help to prevent an incoming breakdown.

If your battery is failing, you may experience the following:

• A red battery-shaped dashboard warning light appears.
• The engine struggles to start (especially in colder weather).
• Lights are dimmer than they should be.
• On-board electronics, such as windows, are slow or have failed.
• The battery is becoming hot when the car is in use (never touch a hot battery).

If your battery has failed completely, these are some of the tell-tale signs:

• Nothing happens when you attempt to start the engine (sometimes you may hear a clicking sound from the starter motor).
• The engine manages to start but then suddenly dies without warning.
• Dashboard lights appear very dim and/or a number of warnings begin to show.
• On-board electrical systems refuse to work.

How long do car batteries last?

Most 12V batteries have an official lifespan of three to five years. Although this is a much longer life than the batteries of the past, the increased amount of technology we use in modern cars means they also take on a lot more strain than they used to.

A modern battery doesn’t only have to crank the engine but there are a host of complicated on-board computers and ECUs to power, too. Add to this features like high-power speakers, electric windows and heated seats and the drain on your battery is huge, and that’s before you put your phone on charge.

Stop-start systems might be good for fuel economy and the environment, but they help to give your battery a proper pasting too. You won’t be surprised to hear then, that flat or dead batteries are one of the most popular callouts for breakdown services.

We’re obviously talking about a car’s 12V battery here. Hybrid cars and electric cars also have much larger and more powerful batteries that either assist an engine or power the car alone. Most do still have a 12V battery as well though. 

How to check a car battery’s condition

As part of your routine maintenance checks, it’s good practice to keep an eye on your battery’s overall condition. There are a number of ways to carry out this inspection, and every process is easy to do. Here are some of the best ways to check your car battery’s condition, all of which should be carried out with the car switched off.

Built-in indicator

The vast majority of modern 12V batteries now have a built-in condition indicator to make checking it a very quick and easy task to do. Sometimes referred to as a ‘magic eye’, these indicators are a small circular symbol that sits within the top of the battery. If the indicator is green, the battery is in good health, if it’s black, you should only need to recharge. However, if it’s red, the battery is dead and it’s time to source a replacement

Visual inspection 

Take a close look at your battery and check for dirt or corrosion on the two terminals. This problem can disrupt the circuit, but it can potentially be fixed by simply disconnecting the battery and brushing away any grime. Also look out for any bulging in the battery’s casing, if you spot this, it could also be leaking acid so be very careful and do not touch it. This problem can be dangerous so the battery must be removed and correctly disposed of as soon as possible. If you’re unsure about safety, consult a professional.

Age

Time takes its toll on all car components and batteries are no exception. Your battery’s lifespan will be displayed on the label along with the manufacturing date. If your battery is past its prime, it’s time to replace it.

Voltmeter

Basic voltmeters can be picked up cheaply from most hardware stores and they’re fairly straightforward to use. First connect the positive wire to your battery’s positive terminal (this is usually red in colour) and then the negative wire to the earth terminal (this is usually black in colour). Once connected, the voltmeter should read around 12-12.7 volts. If the reading is any lower than this, your battery either needs a top-up or it’s struggling to hold a charge. 

How to remove a car battery

Most car batteries are found under the bonnet, however, in some models they are located under the footwell or in the boot instead. If you are unsure then check your owner’s manual. 

When you’ve found the battery, make a careful note of which terminal is which. Once you are ready to remove the old battery, disconnect the negative terminal ( – ) first. Once this is disconnected, you can then disconnect the positive (+) terminal. Be sure to do it in this specific order, otherwise you could cause an electrical short or sparks that can cause damage and injury. 

Once both terminals are safely removed, keep the connectors away from each other and remove any clips holding the battery in place, then lift or slide it out of its tray. There may be additional obscured brackets or bolts holding it in place so do not force it. Once the battery is out, it’s always worth giving the tray a good clean.

How to fit a car battery

To fit your new battery, simply place it into the cage and reverse the removal process, connecting the positive terminal first, then the negative. 

Once the new battery is hooked up, It is likely that you will now need to reset any electronics inside the car – such as the clock or infotainment system. Some infotainment systems may ask for a security code, and this should be located in or alongside your owner’s handbook. 

Car battery types

Finding the right battery for your car isn’t just a case of ‘one size fits all’, but finding the correct fit needn’t be intimidating. Car batteries come in various sizes and types, and each battery has a three- or four-digit code such as 075 or 096T. This code indicates the size, power rating and terminal positions of the battery, among other things, and will help you find the correct replacement.  

Though the traditional lead-acid battery is still fairly commonplace, different cars require different battery types depending on their on-board systems etc. If your car has stop/start, the battery will need to be tuned with the on-board computer, so fitting these particular variants may be a job that’s better suited to a professional. Also, If you fit the wrong type or size of battery to any vehicle, it could cause a severe lapse in performance. As a general rule, always fit the same type and size as the manufacturer’s original. 

Although this may all look confusing, A quick look at the owner’s manual should have all the information you need. Additionally, while the internet is a valuable resource, many suppliers’ websites will allow you to enter your registration number to find the correct specification for your vehicle. 

Plus, if you shop around online, you’ll have a good chance of finding a big discount, along with the added bonus of having your heavy new battery delivered to your door.

How to care for your car battery

Now that you’ve splashed out on a new battery, you’ll want to protect your investment. If you don’t use your car that often, many modern chargers have sophisticated programmes to maintain the level of charge – which is why many classic car owners swear by these products.

These smart chargers vary the current that they pump into the battery in order to prolong its life. They can even be left attached to a car for long periods of time, and just top the battery up gently. Hence they are often referred to as trickle chargers. Plus, if an older battery is showing signs of being on its last legs, one of these products might be worth a try first.

How to dispose of a car battery

Car batteries can be very hazardous to the environment if they are not disposed of properly. In fact, it’s illegal to simply chuck a car battery in the bin, not to mention potentially dangerous. Fortunately, the process for correctly and responsibly recycling car batteries is easy. 

Several battery recycling centres, car parts stores and garages offer a battery-disposal service, many of which are free of charge. Once you’ve handed over your old battery, these service providers will safely drain the battery, remove any other harmful materials and then recycle as much of it as they can. 

Can you change the battery in an electric car?

Electric cars have the same 12V battery as hybrid and combustion models for powering the same types of on-board electronics, such as windows and infotainment systems. You can indeed change this battery using the same process as mentioned above.

However, you must never go near the main battery pack or any other components that are powering the EV itself. These carry an extremely high amount of electricity and can be very dangerous or even fatal if they are interfered with. Always consult a trained professional for any work on these components.

Jump starting

If you’re away from home (or a garage) and find yourself with a flat battery, a jump start could help you to get moving again temporarily. You’ll either need a kind person with another car or your very own jump start pack. 

If you want to learn how to jump start a car, we have a full in-depth guide with everything you need to know.

Need to top-up your battery? Find out more about the best battery chargers…