We know you can't always make it into the shop for a battery test. Here's how to check your car battery at home with nothing more than your eyes and, ideally, a multimeter, plus how to tell when it's time for a proper test.
Safety first
Batteries contain acid and can deliver a lot of current if a tool shorts across the terminals. Wear safety glasses and gloves, take off rings and watches, and keep metal tools away from both terminals at the same time.
Step 1: Visual inspection
- Mounting. Check the battery is held down firmly. A loose battery vibrates itself to an early death.
- Terminals. Look for white or green corrosion and loose clamps. Both cause hard starting even on a good battery.
- Case. Look for acid leaks, swelling, bulging sides or a split case. A battery that has swollen or vented has been overcharged or overheated and should be replaced.
Step 2: Check the resting voltage
If you have a multimeter, set it to DC volts and measure across the terminals with the engine off. For an accurate reading the car should have been sitting for a few hours, so the battery isn't still carrying surface charge from driving.
- About 12.6V or higher: fully charged.
- About 12.4V: roughly 75% charged. Worth a charge.
- 12.2V or lower: about half charged or less. Charge it and test again.
- Below 12V: flat or failing.
Step 3: Good voltage but still won't start?
A battery can show over 12V at rest and still fail under load, because voltage alone doesn't show how much starting current it can deliver. That needs a battery or load tester, which measures cold cranking performance.
A common cause is sulphation. When a lead-acid battery sits partly discharged, lead sulphate crystals build up on the plates and reduce how much charge it can hold and deliver. Short trips, long periods parked up and undercharging all speed it up.
Get a free battery test in Townsville
Bring your car or battery into our Garbutt shop for a free battery and charging system test. We'll check the battery under load and test your alternator, so you know whether it's the battery or something else. If it needs replacing, we can fit a new one from our car battery range, or come to you with our mobile battery replacement service. We'll also recycle your old battery.
Talk to us about your setup
Not sure what's going on with your battery? Visit us at Unit 1, 66 Pilkington Street, Garbutt, call 0459 364 303, or request a quote online.