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2 April 2025 Car Battery Health Check: How to Test and Maintain Your Battery
Your car battery doesn’t only start your engine and send power to the ignition system, but it also serves as a power bank for key electrical car devices, such as the lighting and infotainment system, working in conjunction with the alternator. Once the car starts moving, it acts as a voltage regulator.
Unfortunately, car batteries don’t last forever with a typical replacement interval of 3 to 5 years. They can lose their charge or deteriorate due to factors like age, weather conditions, or constant use. Monitoring battery health is vital to avoid unexpected breakdowns and ensure reliable performance.
How to check car battery health
To ensure your car's battery is in good health, you should start by checking the voltage. This is an easy way to identify if the battery is dead or simply weak. Anything under 11.8V indicates that the battery is dead or heading towards the grave.
Additionally, it’s important to check the battery terminals for corrosion and ensure they’re tightly connected. If they look grimy, the dirt may be causing connectivity problems. If your battery fails the test and visual inspection, it may be time to replace it to avoid being stranded with a dead battery.
Many modern vehicles have a battery charge warning system that alerts you when there is an issue with the battery charge or voltage by triggering a warning light on the dashboard. This typically looks like a red battery symbol.
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Car battery voltage range and test
When the engine is switched off, the voltage should be somewhere between 12.4V and 12.7V in a healthy battery. If the reading is below 12V, it's a warning sign that your battery is losing charge due to being drained by lights and other devices, a faulty alternator, or simply ageing or damage.
When the engine is switched on, the car alternator should increase the voltage to about 13.7V to 14.7V, demonstrating that it is successfully recharging. If the charge is too low, make sure to check both the alternator and the car battery for signs of damage/wear.
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How to test a car battery with a multimeter
Testing your car battery with a multimeter is fairly straightforward:
- First, set your multimeter to DC voltage (typically marked as “V” with a straight line).
- Then, ensure the car is turned off before connecting the multimeter leads to the battery.
- Carefully remove the terminal covers. Connect the red multimeter lead (positive) to the positive terminal first and then attach the black lead (negative) to the negative terminal.
- Check the reading and compare it with the standard values for when the engine is off (see section above).
- A healthy battery should stay above 12V even when the car is switched off. Leaving a wet-cell battery undercharged for long periods can cause sulphation where a buildup of crystals weakens the battery preventing it from holding a charge.
- When disconnecting the multimeter, make sure to remove the black lead from the negative terminal first before detaching the red lead from the positive side to prevent accidental short circuits. Reattach the terminal covers securely.
- Check the vehicle owner’s/repair manual for more maintenance recommendations.
How to test a car battery without a multimeter
If you don't have a multimeter, there are still a few methods to test your car battery's health. Here are some common alternatives:
Headlight test:
Turn on your car’s headlights, then observe their brightness. If the lights are dim or flicker, it may indicate a weak or dead battery. A healthy battery should keep the headlights at normal brightness.
Click test:
When you turn the key to start your vehicle, if you hear a rapid clicking sound but the engine doesn't start, it's often a sign that your battery is weak or dead. A weak battery may not supply enough current to the starter motor, resulting in the clicking sound.
Jump start test:
If your car struggles to start or doesn’t start at all, the battery might be dead. Try jump-starting the car. If it starts right away, it’s likely your battery is weak or dead.
These tests can help you identify a battery issue, but for a more accurate diagnosis, it's recommended to use a multimeter or take your car to a professional.
Battery drain test
To test for a parasitic battery drain, make sure the engine is switched off, disconnect the negative battery terminal, and connect a multimeter in series (set to DC amps). Ensure all electrical devices are switched off, and wait for the vehicle’s modules to enter sleep mode.
A reading above 50mA indicates excessive parasitic drain. Remove fuses one by one to identify the faulty circuit. Once the drain drops, check the components on that circuit for faults. Common culprits include interior lights, alarms, or faulty modules. Repair or replace as required.
How to test a Start-Stop battery
Tips for testing a start-stop battery:
- First check the voltage using a multimeter – a healthy start-stop battery should read around 12.4V–12.8V when fully charged. See the instructions above.
- Perform a cranking test – use a specialised battery tester designed for AGM/EFB batteries. Cranking voltage should not drop below 9.6V. This will determine how effectively the battery delivers power when starting.
- Check the charging system – make sure the alternator provides 13.5V–14.8V while the engine is running.
- Test the internal resistance of the system – use an advanced battery tester to measure internal resistance, which should be low. See owner’s or repair manual for exact values.
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What car battery health is bad?
A car battery's health is considered bad when it shows signs of reduced capacity or failure to hold a charge. When the capacity drops below 80% of the original rated capacity, you’ll start to notice significant performance issues. If the battery struggles to start the engine, especially in cold weather, or if it needs frequent jump-starts, it likely indicates poor health.
Additionally, a battery that is more than 3-5 years old, or one with corroded terminals or leaks, is at risk of failure. A bad battery can also cause electrical issues in the car, such as dim lights or malfunctioning accessories. It's important to test the battery regularly to ensure it is functioning properly before it completely dies.
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How long does a car battery last?
As a rule, a car battery should last between 3 and 5 years, depending on factors like the climate, driving habits, product quality, and maintenance. In warmer climates, batteries tend to wear out faster due to the increased stress on the battery from heat. Cold temperatures, on the other hand, slow down the chemical reactions inside the battery, reducing deterioration.
Frequent short trips don't allow the battery to fully charge and can thereby shorten its lifespan. Regular maintenance, such as cleaning the terminals and checking for corrosion, can help extend the battery's life. If your battery is nearing the 3-year mark,you should start monitoring its performance and consider getting it tested to avoid unexpected failures.
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