How healthy is this battery?

Independent battery tests in Australia

These plug a small tool into the car's diagnostic port and give a written report with a health score, so they suit a buyer checking someone else's car. They work on most EVs and plug-in hybrids, but not regular hybrids yet.

Checking the battery by brand

Tesla

Teslas can test themselves. On software 2025.8.3 or later, go to Controls › Service › Battery Health. The car needs to be at 20% or less and plugged into a home AC charger (5 kW or more), and the test can take up to 18 hours. It can only run once every six months, so ask the seller to run it before you inspect, then show you the result in the car or the Tesla app.

Nissan Leaf

Count the battery capacity bars on the right of the dash: 12 is full health. The first bar goes at roughly 85% health, and each one after that is about 6%. For an exact figure, the LeafSpy Pro app with a Bluetooth OBD2 adapter shows SOH and cell voltages. The Leaf's air-cooled battery wears faster in hot climates, so this check matters most.

Hyundai and Kia

A dealer can print SOH, cell voltages and battery faults with factory tools, and this is the figure that counts for warranty. Apps such as Car Scanner can read SOH through an OBD2 adapter, but Ioniq 5, Ioniq 6 and EV6 often show 100% for years because of a hidden buffer, so also compare usable kWh with the car's spec.

BYD

The BYD app doesn't show battery health. Ask a BYD dealer or a workshop with the right tool for the SOH and any fault codes in writing, or book an independent test.

MG

Some owners read SOH with apps such as Car Scanner or A Better Routeplanner and a Bluetooth adapter, but how the figure is worked out isn't published. For a buying decision, use a dealer printout or an independent test.

Plug-in hybrids

Outlander, Sealion 6 and other plug-ins can usually be tested by the independent services above. Check the electric-only range on a full charge too.

Toyota and Lexus hybrids

Regular hybrids aren't covered by the independent EV tests yet. Ask for the Hybrid Health Check results from Toyota or Lexus servicing: these annual checks are also what keeps the extended hybrid battery warranty going.

Check it yourself

• App and adapter: a Bluetooth OBD2 adapter plugs in under the dash, and an app reads the battery data. Use a quality adapter and unplug it when you're done: some cheap ones are insecure, and some cars set off the alarm if one is left in.
• Range test: charge to 100%, note the range estimate, then compare it with the claimed range for that version. It's rough (weather and driving style change it), but a big shortfall is a red flag.
• Read the dash: look for battery or charging warning lights, and check that fast charging starts and ramps up normally.

Red flags

• SOH well below average for the car's age and kilometres, or a large gap between the highest and lowest cell voltages.
• Battery recalls not done: check the VIN at vehiclerecalls.gov.au. Our recall check lists the serious ones.
• A seller who won't allow a battery test.
• Little warranty left and a battery that is already near the warranty threshold.

What the numbers mean

• Battery health (state of health, or SOH) is how much the battery holds now compared with new. Most EV batteries lose about 1–2% a year, often a little more in the first couple of years, then level off.
• Km until 70% takes how much this battery has lost so far and assumes it keeps ageing at that rate. Because batteries slow down as they age, the real figure is usually higher.
• Range at 100% mode compares the range the car shows when full with its range when new. Teslas show a steady rated range, so it's a good guide there; other brands base it on recent driving and weather, so treat it as rough.
• Plug-in hybrids have a much smaller battery that's often charged from empty to full every day, so it tends to age a little faster (we assume about 2% a year). We compare the electric range on a full charge with the range when new, and count years rather than km until 70%, because petrol km don't wear the battery.
• Battery warranty uses the maker's Australian terms for that car, counted from its year. Most cover the battery if it drops below 70% within 8 years or 160,000 km.
• Normal ageing is slow. In battery-tester Aviloo's study of more than 500,000 tests (2022–26), EVs at 150,000 km typically kept about 87–94% of their capacity.
• But cars vary. The same study found up to 13.5% difference between the best and worst examples of the same model, so a single car can be well below average.
• Heat and lots of fast charging wear batteries faster. See what wears out an EV battery.
• Before you buy, get a certified battery test (mobile tests start from about $200) or a dealer printout: see independent battery tests above.

More on buying used

• Pick my used car: our top three used EVs and hybrids for your budget.
• Used price checker: is the asking price fair?
• Used EV checklist (printable)
• How long EV batteries last, and what wears them out
• What a replacement battery costs