How to check your car battery's health

When it comes to car maintenance, checking your car battery’s health is something that is often overlooked.

The health of your car battery is crucial for ensuring the peace of mind of a car that reliably starts and won’t leave you stranded.

A well-maintained battery will start an engine without trouble, power electrical systems, protect crucial components, increase fuel efficiency, and reduce the likelihood of a breakdown.

To keep your car battery in good order, it’s important to check it regularly for signs of age and poor condition - such as corrosion or an inability to hold charge - and replace it when necessary.

Proper care can extend its lifespan and save you from unexpected troubles down the road.

This guide looks at monitoring the status of your car battery. But remember, if you are unsure on how to fix the issue, speak to a mobile mechanic.

How to check a car battery

Checking your car battery is a straightforward process, and there are a few methods to ensure it's in good condition.

However, it is important to remember that the battery is an essential and potentially dangerous component, so if you are unsure, leave it to the mechanic, or take it to a trusted local garage.

Before you get started, check for any leaks. Any fluid coming from the battery could be acid leaking out of it, which requires immediate attention from a skilled mechanic as it can cause serious damage to surrounding components and is harmful to skin.

Whilst you are doing that, look for any corrosion or white or grey deposits around the battery terminal.

Corrosion can prevent proper contract with the battery’s electrical connectors and should be cleaned off. This will require a specialist cleaning formula. An experienced mechanic will know what to do.

The car battery is usually located on either side of the engine bay, sometimes under a plastic or fabric cover, and will be obviously marked.

It is important to check the battery case for any visible cracks or bulging. If the battery’s outer casing is damaged, it will likely need replacing.

Before you check the rest of the system, ensure the battery terminals are securely connected. Loose connections can cause intermittent starting problems – and damage the battery over a period of time.

At a garage – or with a mobile mechanic – a handheld battery tester can be used.

This is a tool specifically designed to check the health of your car battery. It usually provides a quick reading on the battery’s charge and health.

It will state whether it is weak or needs replacement. If this isn’t the case, then there is likely another issue with the vehicle.

Your car owner’s manual will tell you what the reading should be if the battery is in good health.

• How long do car batteries last?
• Types of car battery and what they mean for you
• What to do if you have a flat battery

How to check a car battery with a multimeter

A multimeter is a tool used by professional mechanics to measure the electrical values from a car battery – such as voltage, current, and resistance.

It is an important safety instrument to ensure the battery can start the car and keep it running without the risk of it leaving you stranded.

The multimeter will give an indication of the battery charge, so is usually the first thing that will be used to check the status of a battery.

Depending on the model of car battery and multimeter, the mechanic will need to set it up and then place the red (positive) lead on the battery’s positive terminal and the black (negative) lead on the negative terminal.

The negative lead can sometimes be blue depending on the vehicle make and model.

The car owner’s manual will detail the correct readings. The multimeter will let the mechanic know if it us over or undercharged.

If it drops too low, then the battery may need charging or replacing.

A similar test can be carried out while the engine is running. This will also be able to test for a faulty alternator.

Signs of car battery issues

Although it is advisable to get a mechanic to conduct the necessary checks on your car battery, drivers should always look out for signs of battery failure.

Common signs of battery issues include:

• Car is slow to start or requires multiple attempts to start
• Headlights or dashboard lights appear dim intermittently, especially when the engine is idling
• Battery car dashboard warning light comes on

Are you experiencing a car fault, warning, or mechanical problem on your road trip? Find a local mechanic or book a mobile mechanic with the RAC.