If the battery is swollen or leaking, or you're stuck on the road
A cracked, swollen or leaking battery needs replacing, so don't try to jump-start it and keep your hands away from any acid. If the car won't start somewhere unsafe, get everyone away from the traffic, put the hazard lights on if they still work and call roadside assistance if you have it. If anyone is hurt or in danger, call 000.
What the motoring clubs say about battery life
| How long it lasts | Worth knowing | |
|---|---|---|
| RACV | Lead-acid: three to five years. AGM: five to seven years | An AGM battery may not last as long in a car with stop-start |
| NRMA | Three to five years | Start paying close attention after three years |
| RAC WA | Three to five years, on average | The weather and how you use the car both change it |
| RACQ | 38 to 48 months, on average | It has also seen one of its batteries come out of a car after eight years |
| RACT | 3 to 4 years | Long idle spells or mostly short trips bring the end closer |
What shortens a battery's life?
Short trips. The RACV says drives under 20 minutes don't leave much time for recharging. RAC WA adds that even a regular daily run isn't always enough to fully charge a battery that's been run flat.
A car that sits. A parked car still draws a small current with the key out. RACQ's view is blunt: drive it once or twice a week and the battery isn't really being used. RAC WA says a car left for more than two weeks will likely need its battery looked after.
Heat and cold. NRMA says extreme heat or cold can shorten battery life, and RAC WA says a battery older than three years is less likely to handle extreme weather. An old battery can seem fine for months, then give up in the first hot spell or on a frosty morning.
More electrics. RACQ says nearly everything in a car is electric now, which puts more demand on the battery and is part of why they don't last as long as they did. RACT adds accessories such as dash cams.
Its life before your car. RACQ also counts how long a battery sat on a store shelf before it was fitted, and whether it was kept at full charge.
Which kind of battery does your car have?
Plenty of petrol and diesel cars take a standard lead-acid battery. Many modern cars need an AGM battery (a sealed type that recharges faster) to work properly, the RACV says, and NRMA says cars with stop-start need one built for heavier loads.
So a replacement has to match. NRMA's list is the right size and type, the posts in the right place, and enough cold cranking amps (the power it takes to turn over a cold engine). A battery that fits the tray can still be the wrong battery.
How to tell if your car battery is dead
Listen when you try to start it
A slow, laboured crank means the battery is struggling. A clicking sound with an engine that won't come to life usually means it's flat.
Look at the lights and accessories
If the engine won't crank and the lights and accessories are off too, NRMA says that points squarely at a flat battery. Bright lights with no crank can point at the starter motor instead.
Look at the terminals with the engine off
Loose or corroded terminals can stop power reaching the starter motor. Blue or green residue, or a scaly build-up, is what you're looking for. Don't touch it, just tell the mechanic.
Only jump-start it if you know how
Follow your owner's manual, because the RACV warns that an incorrect jump start can cause trouble with the car's electrical systems. If you're not sure, call roadside assistance.
Have it tested, not guessed
If it goes flat again soon after, there's a fault somewhere. RAC WA says these symptoms can also point to a faulty alternator, so test the battery and the charging system together. The RACV says a reading under 12.4 volts, taken after the car has sat overnight, counts as discharged.
Signs a battery is on its way out
- The engine turns over more slowly than it used to, most of all on a cold start.
- Dim lights, slow wipers, a silent radio or dead remote locks.
- A battery icon on the dash.
- Blue or green residue on the terminals.
- A swollen, misshapen or cracked battery case.
- You've needed more than one jump start lately.
How often should you replace your car battery?
There's no set date. Replace it when a test says it's failing, or when it's well past three years and you're about to rely on it far from home.
NRMA suggests a battery health check once or twice a year, or before a long road trip, and says that matters most from the three-year mark. A tester connected to the terminals takes under 10 minutes and can pick up weak cells.
A service is the other natural moment. The RACV lists a battery test as part of a minor service, so ask what the result was.
What a good battery replacement covers
- A test first, so you know the battery really is the problem.
- A check of the charging system, so the new battery doesn't go the same way.
- The right type for the car: lead-acid or AGM, and made for stop-start if the car has it.
- The size, post layout and cold cranking amps, written on the estimate.
- Clean, tight terminals when the job's done.
- The new battery's warranty terms, in writing.
What you can do, and what to leave
You can
- Work out the battery's age from your service invoices or any date sticker on it.
- Give the car a longer run each week if it mostly does short trips.
- Switch off lights and accessories before you walk away.
- Use a suitable charger if the car will sit for weeks, following the charger's instructions.
Leave to the mechanic
- Load testing the battery and testing the charging system.
- Fitting a new battery, especially in a stop-start car.
- Anything to do with a cracked, swollen or leaking case.
If it were our car
We'd find out how old the battery is this week. Under three years with no symptoms, leave it alone. Past three years, have it tested at the next service, or sooner if a long trip is coming up. If it's already slow to crank, don't wait: a battery that's labouring on a cold morning rarely gets better by itself.
Who should look at it?
Most mechanics can test and change a battery, and a mobile mechanic can do it where the car is parked. If batteries keep dying and nobody can say why, an auto electrician is the right person, because a slow power drain takes patience and the right gear to trace.
Tell us the job and the car. A local mechanic who specialises in your car.