Car Battery Testing at Home

There’s never really a good time to discover that your car battery has gone flat. You certainly don’t want your car battery to die when you’re away from assistance.

You can minimise the risk of this happening by making sure that lights aren’t accidentally left on. Most modern cars have lights that automatically switch off when you turn the engine off. But internal lights can drain the battery, which may happen when passengers forget to turn them off or when car doors are not shut properly.

Another way to reduce the risk of your car battery running flat is to regularly test your battery. Thereare a few ways you can test the strength of your car battery at home.

Testing your car battery at home without equipment

There are three ways you can test your car battery yourself without needing any special equipment.

1. The light and load test

Put the key in the ignition and turn the car lights on – without starting the engine. Leave the lights on for 10 to 15 minutes. After that time has passed, start the engine and pay attention to the brightness of the headlights.

If the headlights dim noticeably when the engine starts, the battery doesn’t pass the load test. A “healthy” or full-charged battery should be able to handle the load of the lights and the engine. If the lights dim, then the battery is not handling the load as it should.

Bring your car to us at Mt Roskill Collision Centre and we can help you determine whether your car battery needs to be replaced.

2. The click test

Start your engine and listen. It’s a good idea to keep the radio volume down low when you’re starting your car so you can listen for any sounds your car makes when you start it. You should hear a soft roar of the engine starting, settling into a smooth “purr”.

If you hear a click (or series of clicks) when you start your car, but no sound of the engine starting, you most likely have a problem with your car battery. The click is the sound of the switch that activates the engine starter motor. There’s enough juice in the battery for the starter switch, but not enough to start the engine. It’s time to have the battery – and the other connection components –
checked out.

3. The corrosion check

This is a visual check to determine if your battery needs replacing. With your car turned off (i.e. the engine is not running), lift the bonnet and locate the battery. Do you see any corrosion on the battery?

Some amount of corrosion around the battery is normal, but there may be greater amounts if the battery is nearing the end of its life (around the four or five year mark) or if your vehicle has been sitting idle for an extended period of time.

It is possible to clean small amounts of corrosion on your battery if you know what you’re doing. We suggest, however, that you get in touch with us to check the state of your car battery.

Testing your car battery at home with equipment

Other than the three ways of checking your car battery at home that we’ve mentioned above, you can also check your car battery using a multimeter or voltmeter. A multimeter or voltmeter is a small hand-held device you can use to check how much charge or voltage your car battery has. We recommend following the instructions that come with the multimeter or voltmeter.

To give you an idea of what is involved, the steps include:

1. Leave the car to sit with the engine off for several hours (preferably overnight).

2. Unclip or remove the plastic cover from the top of the battery.

3. Make sure that nothing metal touches the two battery terminals (don’t rest any of your tools on it).

4. Hold the red probe to the positive terminal (+) and the black probe to the negative terminal (-).

5. If your car battery is fully charged, you should see a voltage reading of around 12.5 or 12.6 volts when the car is not running (its resting voltage). When the car is running, a fully charged battery will rise to somewhere between 13.5 and 14.5 volts.

6. If you’re getting a negative reading with a minus in front of it, you've got the probes the wrong way round. If you’re getting a reading of 12.2V, the battery is only 50% charged. Anything below 12V means the battery is discharged/dead/flat – the voltage of the battery is below what is needed to safely run your engine.

If your car battery doesn’t pass the tests mentioned above, or you’re getting a low ready on a multimeter or voltmeter, get in touch with us to have it checked out. Your battery may be nearing the end of its life and you don’t want to get caught out with a flat battery.

To stay safe on the road, give us a call on 0800 227 762 or contact us online.