If you drive one of the more than 22.3 million registered vehicles on Australian roads,1 chances are you may have experienced the frustration of a flat car battery at some point – or wondered what you’d do if that happened.
Whether you’re behind the wheel of a petrol, diesel, hybrid or electric vehicle, car battery replacement is a common headache. In fact, car battery problems are the main reason drivers call Youi for roadside assistance – well ahead of tyre trouble or mechanical faults.
But running out of charge doesn’t mean battery replacement is inevitable, or that you need to be stranded for long.
To help you navigate car battery issues, we’ve prepared this guide that explains why batteries go flat, which warning signs to look out for, and why different batteries may need to be treated differently.
We’ll also take you through your options, from jump starting your car to replacing the battery, as well as covering how car insurance may help you get back on the road with a new or recharged battery.
Why do car batteries go flat?
The standard 12-volt car battery remains a crucial component in almost all cars on Australian roads today – including most modern hybrids and EVs.2 In traditional fuel cars, it powers the starter motor and runs the electronics when the engine is off.3 In electric and hybrid vehicles, it supports the main high-voltage battery and powers essential electrical features like lighting, alarms and infotainment.2
Depending on the make and model of your vehicle, here are some common reasons for a flat car battery:
- Your battery has reached the end of its life – car batteries typically last three to six years3
- Problems with the alternator – which recharges the battery3
- Headlights or interior lights have been left on – more common in older models3
- Accessories, such as the stereo, have been left on while the car isn’t running4
- Your car hasn’t been driven often enough – batteries can gradually degrade if a car sits idle for too long2
- Software glitches have prevented proper charging or caused excessive discharge2
- Faulty switches on the glove box or brake lights3
- Loose or corroded battery terminals.3
Flat battery right now? Here’s what to do
Whether your flat battery has left you stranded in your driveway, or you’ve been forced to pull over on a busy highway, staying safe and getting help if you need it should be the first priority.
Once you’ve confirmed that everyone is safe, you can turn your mind to the technical problem. Depending on your circumstances, here are some choices you might consider:
Jump start your car
If your engine won’t start, jump starting – using another vehicle or power source to charge your battery4 – might be an option.
For that reason, keeping jumper cables in your boot as part of your car emergency kit may be a good idea.
However, like most things to do with car batteries, this comes with a word of caution – especially for newer vehicles. It’s always a good idea to check your owner’s manual before attempting anything yourself.4
That’s because jump starting can cause damage to the electronic control unit (ECU) – or engine computer – if there’s a power surge.5
Replace your car battery
If your car battery can’t be jump started, it will likely need to be replaced.
But before you roll up your own sleeves, the automotive experts at the Victorian Automotive Chamber of Commerce (VACC) and Motor Trade Association SA/NT (MTA SA/NT) recommend proceeding with care.
“Replacing a battery on an older car – with a lead-acid battery – was something many drivers could confidently do themselves with basic tools,” says Rod Lofts, Senior Technical Writer at VACC.
“However, on a modern vehicle, the same job can trigger a cascade of issues across the car’s electronics that can be expensive and time-consuming to resolve,” says Lofts.
There are three main types of car batteries, says Lofts:
- Standard lead-acid
- Enhanced flooded battery (EFB)
- Absorbent glass mat (AGM).
If your car is older and has a lead-acid battery, it may be safe for you to change your own battery, according to the MTA SA/NT.
But both automotive organisations advise strongly against motorists attempting to change their own EFB or AGM batteries.
“The era of the ‘universal DIY battery swap’ is drawing to a close,” says a MTA SA/NT spokesperson.
Call roadside assistance
If you don’t feel comfortable – or it’s not recommended or safe – to attempt the DIY option, you might prefer to call for roadside assistance.
At Youi, problems with car batteries make up 45% of callouts to Roadside Assist, and this service comes standard with Comprehensive car insurance, as well as Comprehensive motorcycle insurance.6
“Flat batteries are the most common reason our comprehensive insurance customers call for help, and we can assist by either jump-starting their car, or arranging for a replacement car battery, subject to availability,” says Marni Jackson, Youi’s Head of Product – Vehicle and Lifestyle.6
“Do keep in mind though that drivers will need to cover the cost of the car battery itself.”
Safety considerations when changing a flat battery
“Battery replacement carries real risks, to both the person and the vehicle,” cautions Lofts.
According to the VACC, hazards include:
- Arc flash7 and current surge – A type of electrical short circuit, this is caused by connecting or disconnecting terminals in the wrong order, or allowing tools to contact the bodywork or engine, risking personal injury and damage to vehicle electronics.
- Incorrect polarity – Fitting the battery the wrong way round can cause serious damage to your car’s electrical systems.
- Acid leaks – Damaged batteries can leak acid.
- Computer memory loss – Removing the battery disconnects power to all onboard computers, which can cause loss of window and sunroof calibrations, for example.
When to call the professionals
While there are some car problems you might be able to repair on your own, some jobs are simply best left to the experts.
The VACC recommends professional assistance if:
- You are unsure of the correct battery type, access procedure, or connection sequence for your specific vehicle.
- The vehicle has a Battery Management System (BMS) – identifiable by a small black sensor box on the negative terminal.
- The battery has failed completely, not just discharged.
- The vehicle continues to go flat after a jump-start or recharge.
Lofts also warns about implications for car warranties:
“DIY battery replacement on a modern vehicle may void manufacturer or extended warranty coverage if the process causes damage to the electrical system, even unintentionally.”
How to change a car battery – step-by-step guide
Yes, we’ve already talked about safety. But we can’t emphasise enough the need to take precautions – and to always check the owner’s manual because the steps you’ll need to take can vary, depending on the make and model of your car.8
If you have determined that it’s safe to change your own lead-acid car battery, the MTA SA/NT has outlined the following key steps.
Preparing to change a car battery
- Wear protective gear, including safety glasses and battery electrolyte-resistant gloves.
- Work in a well-ventilated area, away from open flames or sparks.
- Secure the vehicle – ensure the engine is off and the car is in ‘park’ – or ‘neutral’ with the parking brake engaged – and remove keys from the ignition.
- Lower a window – some central locking systems can ‘cycle’ when power is lost and reinstated, potentially locking you out of the car.
- Get a socket set or spanner and a wire terminal brush.
H3: Disconnecting and safely removing a car battery
- Identify the Terminals – locate the Negative (-) terminal, usually marked in black, and the Positive (+) terminal, usually marked in red or with a plastic cover.
- Disconnect the Negative First – Use the required tool to remove the fixings on the negative terminal. Remove the cable and tuck it aside away from the battery.
- Important – Removing the negative first breaks the ground circuit, preventing accidental sparks if your metal tool touches the car’s frame.
- Disconnect the Positive – Remove the positive cable next.
- Remove the Hold-Down – Unscrew the bracket or clamp holding the battery in place.
- Lift and Inspect – Carefully lift the battery – they are heavy so it may be best to use proper lifting technique. Inspect the battery tray for rust or debris and clean if necessary.
H3: Connecting a new battery
- Install the new battery – Place the new unit in the tray, ensuring it is level. Secure the hold-down bracket.
- Reconnect in Reverse – Connect the Positive (+) cable first, then the Negative (-) cable last. Ensure both are tight, cannot be moved by hand and apply protective coating to terminal posts.
H3: Testing your new battery
According to the VACC, this is another job best left to the experts.
“After a new battery is fitted, professional workshops use specialised battery testers to verify that the battery is performing correctly and that the charging system is functioning within specification,” says Lofts. “These tools are beyond the scope of the average home mechanic.”
H3: Disposing of your new battery
Never put an old car battery in your household waste or recycling bin.9 Batteries contain hazardous materials that can start fires, emit toxic gases or cause acid burns when compacted or punctured in waste trucks or at recycling facilities.9
Instead, take them to an authorised drop-off point. You can contact your local council, or search Recycle Mate, to find a car battery recycling facility near you.9
H2: How much is a car battery replacement?
In Australia, the average car battery replacement cost will generally depend on the make and model of your vehicle and the battery type, and whether you’re using a mobile car battery replacement service. However, the average 12-volt battery replacement could cost around $570 for those requiring a call-out.10
H2: Warning signs your battery may need replacing
There are often clues a battery is dying; here are some signs to look out for:11
- Sluggish engine, or car takes longer to start
- Car frequently needs jump-starting
- Interior lights weak or flickering
- Battery casing itself looks old, swollen or damaged
- Corrosion on battery terminals
- Battery icon illuminated on dashboard or driver’s display.11
H2: What can you do if your EV runs out of battery?
Even the most organised drivers can still get caught out with a flat EV car battery.
“If your EV runs out of charge, and you have car insurance for an EV with Youi, Roadside Assist can help get you back on your way, 24/7,” says Marni Jackson, Youi’s Head of Product – Vehicle and Lifestyle. “This might mean a tow to the nearest charging station, where you may be required to pay a charging station fee, or the nearest place of safety.”6
H2: How often should you change a car battery?
The average car battery will last three to six years, but lifespan between batteries and vehicles may differ, and depend on factors including:11
- Total number of discharge cycles
- How the battery has been maintained
- Condition of the vehicle’s charging system.11
H2: How to help prolong the life of your car battery
Taking regular long trips is one of the best ways to preserve your car battery because it gives your vehicle’s alternator enough time to fully recharge the system.11
For Electric Vehicles, avoiding frequent use of fast or ultrafast chargers and charging your EV or hybrid car battery only as fast as needed as often as you can, may extend the battery life.11
If you like the idea of having some backup when your car battery or something else doesn’t quite work as you expect it to, you might like to take a look at Youi's Comprehensive car insurance – where Youi Roadside Assist comes standard – or consider starting a quote with Youi to see if there’s a policy to suit your needs.
1 Source: Australian Government – Australian Infrastructure and Transport Statistics – Yearbook 2025, September 2025
2 Source: Drive – ‘It’s crucial’: Why the 12V battery is essential to your car’s life, August 2025
3 Source: Drive – Why does my car battery keep dying?, November 2024
4 Source: carsales – How to jump start a car, April 2024
5 Source: Fleet Auto News – Beware the risks of jump starting, March 2023
6 Youi Roadside Assist available with Comprehensive policies only. Exclusions, limits and additional fees may apply. Cover not available within the first 24 hours of taking out, or upgrading to, Comprehensive cover. For full details, see the Roadside Assistance T&Cs, Car PDS and Motorcycle PDS.
7 Source: Energy Safe Victoria – Arc flash hazard management, December 2022
8 Source: CarsGuide – How to disconnect a car battery, May 2023
9 Source: Qld Government – Don’t bin your batteries, May 2023
10 Source: CarsGuide – How long does a car battery last?, April 2025
11 Source: CarsGuide – Charge Your Car Day a timely reminder for a battery health check-up, October 2024
12 Source: Australian Government – Electric vehicle maintenance and servicing, 2024
