Couple sitting on car in parking lot
Tips & tricks

Why does my battery go flat

Flat batteries always seem to happen at the most inconvenient times, but what makes them go flat?

There are a few reasons why your battery could have gone flat. The most common reasons are:

  • End of life - most car batteries are made to last between two and six years with the average life being four years. Batteries are filled with acid and start deteriorating internally from day one. Heat, cold, vibration, and electrical loads all go towards reducing the lifespan.

  • Leaving your lights on - we've all been there. Forgetting to turn your headlights or interior lights off will quickly drain your battery.

  • Short trips - as your battery is charged by the alternator while you drive, short driving (under 20 minutes) won't allow for much recharging time. So, if you're only driving a short way each time, this may mean your battery goes flatter sooner than you expect.

  • Parked cars - did you know your car uses a small amount of current when the key is not in the ignition? This means if your car is parked for a long period, the battery will drain over time without the alternator recharging it as you drive.

  • Extreme temperatures - unusually hot or cold weather can weaken battery performance, hence why winter sees quite a few flat batteries across Tassie.

  • Faulty parts - issues like corrosion, leaks, and faulty parts can all shorten your battery's lifespan.

  • Incorrect fitment -modern vehicles are very reliant on having the correct battery technology (Calcium, EFB, AGM, and Lithium) fitted. Some European cars will also run a second battery which can be very well hidden. If the incorrect/sub-standard battery is fitted, even though fully charged, it can cause a no-start situation

  • Other accessories - some dash cameras, reverse cameras, trailer brake controllers, and other aftermarket accessories cause a "parasitic drain" on your battery, slowly but surely reducing your base charge and eventually causing your battery to be too weak to start your car. There can also be faulty components in the vehicle that can cause this issue.

Note: Modern vehicle charging systems will not fully recharge your battery after draining so it's important to have it fully recharged on an appropriate smart charger. Depending on the size of your battery and charger, this can take up to three or four days.

Where's yours gone flat?

We asked you recently where your battery had let you down and these were the top five spots:

Car parks

Cinema, shopping center, and casino car parks topped our list, with frustrated patrons ready to leave with their goodies discovering they'd be parked up a bit longer than hoped.


While still a hassle, many people had theirs go flat in the driveway which means they could stay happily at home while they waited for help.


Always a busy time of day, lots of parents have been kept back at school a little longer once they packed in their little ones and found themselves unable to leave.


A few of you have also been stuck while driving through for a bite to eat, which is handy, but some unlucky ones had it happen when in line for a COVID test.

Doing my thing

We also got a variety of other answers such as when camping, fishing, on top of the mountain and when in traffic jams.

The common theme throughout all answers was when you least needed it to happen or you were running late for an event.

We'll get you back on the road

Make sure you're cover with roadside assistance. We deliver breakdown service on the side of the road, in a car park or in your own driveway. No matter the time or place, we come to you.