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A flat battery is one of the most common reasons drivers find themselves stuck.
Luckily, testing your car battery and keeping an eye on its health is something you can do easily yourself at home to prevent being stranded.
Whether you’ve noticed the lights dimming or you simply want to stay on top of your car maintenance, this guide will help you confidently test your car battery’s health.
Get a headstart with our range of quality battery testers, available with free Click and Collect to your local Euro Car Parts store.
What’s Included In This Article?
Why is checking your car battery important?
Signs your car battery might be failing
Step-by-step guide to testing your car battery
Why Is Checking Your Car Battery Important?
The last thing you want is to be stranded with a dead battery. By checking it regularly, you can catch a weakening battery early and test it before you get stuck or it becomes a more expensive problem.
Signs Your Car Battery Might Be Failing
If you spot any of these signs, it’s a good idea to test your battery sooner rather than later. Common warning signs that your battery is struggling include:
Slow engine starting
Your headlights appear dimmer than usual
The battery warning light appears on your dashboard
Your car needed a jump start recently
The battery case looks swollen, cracked or there’s a white or blue powdery residue around the terminals
Tools You’ll Need
You don’t need many tools to test your car battery, but it’s worth grabbing these before you get started so that you’re prepared and safe:
A cloth
Not sure which multimeter to go for? Check out our full range of electrical testers and multimeters to find the right one for the job.
Step-By-Step Guide To Testing Your Car Battery
Park on a flat surface and turn the engine switched off. Make sure you’ve put on your gloves and safety glasses before you open the bonnet.
If you don’t feel confident using a multimeter or you just want to do an initial test before going to a mechanic, the first two steps will give you a good indication of your battery’s health without the need for any tools.
Step 1. Locate and inspect the battery
Most batteries are found in the engine bay, however they may also be in the boot or the floor. If it is in the engine bay, prop open the bonnet and find your battery - it’s the rectangular black box near the front. Once you’ve found it, have a quick inspection and check for any cracks or bulging in the casing. If you see either, this is a sign your battery needs to be replaced immediately.
Now look at the terminals – these are the metal connectors at the top – for any white, blue or greenish powdery build-up. If you spot any, gently clean the terminals with a wire brush before testing.
Step 2. Do a quick headlight test
You can do this yourself, but it’ll be much easier if you get someone to help you. Firstly, turn on the ignition and switch on your headlights, but do not start the engine. Leave them for a minute or two and then start the engine. Check, or ask a friend, to see if the headlights go dim or the beam stays steady as the car starts. If they dim, this is a sign your battery is not as healthy as it needs to be.
Step 3. Set up your multimeter
Making sure your engine and all electrical components like your lights are now switched off, grab your multimeter. Turn your multimeter dial to the DC voltage setting and set it to 20V.
Step 4. Connect the multimeter to the battery
Carefully remove the terminal covers on your battery (if you have them) and connect the positive red probe to the positive terminal on the battery first. Then connect the negative black probe to the negative terminal. Make sure the probes are making firm contact with the terminals for an accurate reading.
Step 5. Take a resting voltage reading
With the engine off and all electrics switched off, your multimeter should now display the battery’s resting voltage. You’re ideally looking for a reading between 12.6V and 12.7V. If your reading is below this, try charging the battery fully and re-testing to be sure that there’s an issue. If your battery still fails to hold charge after being fully recharged, it’s time for a new one.
Looking for some more expert advice on car electrics? We’ve covered everything from common electrical problems to look out for to how to change a car battery in our Knowledge Centre.
FAQs
How can I maintain my car battery health?
Once you’ve tested your battery and you’ve found it’s in good condition, a few simple habits will help you keep it that way:
Take regular, longer drives
Avoid leaving any electrics on
Keep the terminals clean
Use a trickle charger
How often should I check my car battery health?
A quick visual check every couple of months is a sensible habit. A voltage test with a multimeter is worth doing at the start of winter and again in spring, or any time you notice any warning signs with your battery.
What voltage should a healthy car battery be?
This will depend on your car and how you use it, but a fully charged, healthy battery should read around 12.6V with the engine off. With the engine running, the voltage should rise to between 13.7V and 14.7V as the alternator charges the battery.