The short version
State of health — SoH — is the percentage of its original usable capacity a battery still holds. It is the single figure that determines what a used EV can do and what it is worth, and unlike kilometres on the odometer it is not written anywhere on the car. Four numbers frame the whole decision:
- 2.3 per cent a year. Geotab’s April 2026 study of more than 22,700 EVs across 21 models put average degradation at 2.3 per cent annually, projecting about 81.6 per cent of original capacity still present after eight years.
- Twice the rate. In the same dataset, vehicles that frequently used high-power DC fast charging above 100kW degraded at about 3.0 per cent a year against 1.5 per cent for the low-power group — roughly double. How a car was charged matters more than how far it was driven.
- 70 per cent. The capacity floor most Australian battery warranties actually guarantee, typically over eight years or 160,000km. Anything above that line is, contractually, working as sold.
- $6,000 to $20,000. The range quoted for an out-of-warranty replacement pack in Australia depending on size — which is what you are really underwriting when you skip the check.
The gap between the second and third numbers is where the money is. A car degrading at the fleet average will comfortably clear the warranty floor for its whole warranted life. A car that lived on 350kW chargers might not, and it looks identical in a listing photo.
Why this suddenly matters here
Because the Australian used EV market has grown up in about eighteen months. A report from the Australian Automotive Dealer Association, AutoGrab and auction house Pickles published on 20 July found used EV sales up 54.6 per cent year on year in the first half of 2026, with plug-in hybrids up 468.4 per cent from a much smaller base, while the broader second-hand market went backwards. Electrified vehicles of all kinds made up 7.1 per cent of used sales.
Prices moved just as hard. Pickles’ average used EV sale price ran from $35,500 in January to a $41,500 peak in April and then down to $31,500 by June, while average selling time fell from more than 60 days in January to under 40 by June. Separately, a March analysis by broker Savvy using RedBook data found a 2022 Tesla Model Y rear-drive down about 48 per cent on its original price and a BYD Atto 3 down about 39 per cent.
Cheap, fast-moving and plentiful is exactly the market in which an unverified battery gets sold. The cars now reaching the second-hand market in volume are the 2021–2022 wave — four and five years old, out of any statutory dealer warranty, still inside most manufacturer battery warranties, and old enough that how they were treated has started to show.
What state of health is, and what it is not
SoH is capacity against original capacity. It is not the same as any of the numbers a car will volunteer to you, and confusing them is the most common mistake in this whole exercise.
| The dashboard range estimate | Not SoH. It is a prediction built from recent driving efficiency, and it moves with weather, tyres, load, speed and the previous driver’s right foot. A car that has been doing short suburban trips in winter will show a pessimistic number with a perfectly healthy pack. |
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| A full charge to 100 per cent | Closer, but still not a measurement. It tells you what the battery management system currently believes, and that belief drifts — particularly on cars that are habitually charged to 80 per cent and rarely calibrated. |
| Odometer reading | Weakly correlated at best. Geotab’s data ties degradation far more closely to charging behaviour and age than to distance. A 120,000km highway car on AC charging can easily be healthier than a 45,000km car that lived on DC. |
| State of charge (SoC) | Different thing entirely — how full the battery is right now. Do not accept a screenshot of a percentage as a health report; check which percentage it is. |
| State of health (SoH) | Usable capacity now, as a percentage of usable capacity when new. This is the number. It has to be read out of the battery management system or inferred by a proper diagnostic test, and it is the number a warranty claim turns on. |
What the degradation data actually says
The best public dataset on this is Geotab’s, published 28 April 2026 from telematics on more than 22,700 electric vehicles spanning 21 models. Its headline: average degradation of 2.3 per cent a year, implying about 81.6 per cent state of health at the eight-year mark.
That number is up from the 1.8 per cent Geotab reported in its earlier study, and the reason is worth understanding because it is easy to misread as batteries getting worse. Geotab attributes the rise to the composition of the newer fleet — more models, newer cars with higher charging capability, and correspondingly more high-power DC charging — rather than to any decline in battery durability. The breakdown by charging behaviour is the useful part:
- Low frequency of DC fast charging: about 1.5 per cent a year.
- High frequency, low power: about 2.2 per cent a year.
- High frequency, high power (above 100kW): about 3.0 per cent a year.
Reasoning beyond the source: run those rates out over a five-year-old car and the spread is material but not catastrophic — roughly 93 per cent SoH for the gentle case against roughly 86 per cent for the hard-charged one. That is around 40 to 50km of real-world range on a mid-size EV. It is a negotiating position, not a reason to walk away. The cars you actually want to find are the outliers below that band, and the only way to find them is to measure.
One thing the data does not support is the folk belief that a used EV is a battery time bomb. On these figures the average pack comfortably outlasts the warranty that covers it. The risk in a used EV purchase is not that batteries typically fail; it is that you have no way of knowing whether the one in front of you is typical.
The four ways to get a number, in Australia
Ranked roughly by how much weight we would put on the result. Prices are as listed by the providers at the time of writing.
| Independent diagnostic test Strongest evidence | The NRMA runs an EV Battery Health Check using diagnostics from Austrian firm Aviloo, delivering an independent emailed report with a score out of 100, current capacity and flagged issues. It is $250 for members and $300 for non-members, currently Sydney metro and Canberra only, weekdays 8am–4pm with two days’ notice, and a patrol comes to the car. NRMA says it covers over 90 per cent of BEVs and PHEVs sold here; conventional hybrids are excluded, and it warns results may not be reliable on a car whose battery has already been replaced or refurbished. |
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| Aviloo’s own test tiers Know which one you are getting | Aviloo sells a FLASH test — about three minutes, machine-learning inference trained on tens of thousands of full tests, quoted at roughly ±3 per cent against the full test — and a PREMIUM test, which analyses the battery across a complete discharge cycle and issues a certificate covering SoH, range and cell-level checks. If a seller waves a certificate at you, look at which test produced it. A three-minute inference and a full discharge analysis are not the same evidence. |
| OBD2 dongle and app Cheap, driveway-friendly, model-dependent | An OBD2 adapter with an app that has a proper connection profile for the car — Car Scanner is the common one, with community-built parameter IDs for Hyundai, Kia, BMW, VW, Renault and others — can read SoH directly from the battery management system in a seller’s driveway. Coverage varies sharply by make, model and year, and generic OBD2 mode without a profile reads powertrain codes only. Verify your exact model and year is supported before buying hardware, and expect brand-specific quirks. |
| The car’s own service tooling Free, uneven, better than nothing | Some cars will tell you themselves. Tesla exposes a battery health report through Service Mode showing a maximum range estimate and degradation against original spec. Third-party access on Teslas in particular can break temporarily after software updates. Treat a manufacturer’s own readout as a strong indicator and an independent test as evidence. |
Our reading, stated as opinion: on a car in the $30,000 range, a $250 to $300 independent report is roughly one per cent of the purchase price to eliminate the one risk you cannot see, and it is worth it — particularly on any car outside its battery warranty, any car whose history you cannot document, and any ex-fleet, ex-rental or ex-rideshare vehicle, where high-power DC charging is the norm rather than the exception. Outside Sydney and Canberra you are currently reliant on the OBD2 route or on whatever a workshop or dealer can produce, which is a real gap in coverage rather than a reason to skip the step.
What the warranty actually promises
Nearly every EV sold in Australia carries a separate battery warranty, longer than the vehicle warranty, and the headline terms cluster tightly: eight years or 160,000km with a guaranteed capacity retention of around 70 per cent. There is real variation at the edges — MG has marketed a ten-year/250,000km battery warranty, and Kia’s seven years sits at the shorter end — so check the specific car rather than assuming the class.
Two features of that structure matter enormously to a used buyer, and both are routinely misunderstood.
The 70 per cent is a floor, not a promise of performance. A pack at 75 per cent SoH has lost a quarter of its range and is not a warranty claim. Given the fleet-average degradation above, a car that reaches 70 per cent inside eight years is a genuine outlier, which is precisely why the number is set there. Read it as insurance against a defective pack, not as a service-level guarantee on range.
The warranty runs with the car, not the first owner. Manufacturer warranties in Australia transfer to subsequent owners; some brands require the transfer paperwork to be done properly — Tesla, for instance, conditions its transferable warranty on the ownership change going through Tesla. So a four-year-old EV typically arrives with about half its battery warranty intact, and confirming that transfer is a five-minute job worth doing before settlement rather than after.
On fast charging and warranty: DC charging is a normal, expected use of a modern EV and does not by itself void anything. What manufacturers exclude is misuse, unapproved or modified charging hardware, tampering and unauthorised repair. Some brands do write conditions around charging patterns into their terms, so if a car has clearly lived on DC, read the actual warranty document rather than a summary — including ours.
Where the law helps, and where it stops
Three separate layers apply, and they cover very different amounts of ground.
| State statutory warranty Licensed dealers only | In NSW and Victoria, a used car from a licensed dealer carries a statutory warranty of three months or 5,000km, whichever comes first, for vehicles under ten years old and under 160,000km. Queensland splits it: Class A, for cars under ten years and 160,000km, is three months or 5,000km; Class B, for older or higher-kilometre cars, is one month or 1,000km. Standard exclusions cover misuse, accident damage after delivery and items on a defect notice. |
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| Australian Consumer Law The broader protection | Consumer guarantees apply automatically to any purchase from a business and cannot be excluded or waived by a contract term. Goods must be of acceptable quality, safe, durable and fit for purpose, and spare parts must be reasonably available. These rights outlast the statutory warranty and are the ones that matter for a battery fault, since durability is judged against what a reasonable buyer would expect of a car of that age, price and description. Unresolved claims go to the state tribunal — NCAT, VCAT or QCAT. |
| Private sale Almost nothing | Buy from an individual and neither the statutory warranty nor the consumer guarantees apply — you get the manufacturer’s remaining battery warranty and nothing else. Victoria states plainly that a statutory warranty does not transfer to a new owner on a private sale. Private is where the cheapest used EVs are, and it is exactly where a paid independent battery report earns its money. |
One ambiguity we flag rather than resolve: Consumer Affairs Victoria lists “batteries” among the components excluded from the statutory used-car warranty. That exclusion long predates electric cars and plainly contemplates a 12V starter battery, but we could not find published guidance confirming how it is applied to a traction pack. If you are buying in Victoria and relying on the statutory warranty rather than the manufacturer’s battery warranty, that is a question to put to the dealer in writing before you sign.
What to do before you hand over money
Our checklist, assembled from the sourced material above and applied to an Australian purchase.
| Ask for SoH in writing, up front | Not a range estimate, not a photo of a charged dashboard. A number, and the method that produced it. A dealer who cannot or will not produce one on a car that is otherwise well presented has told you something useful. |
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| Ask how it was charged | The single most predictive question, given the 1.5 versus 3.0 per cent split in the data. Home AC overnight is the gentle case. Ex-fleet, ex-rental and rideshare cars are the hard-charged case, and their service history usually shows it. |
| Check where the battery warranty stands | Original in-service date, kilometres, the specific term for that brand and model, and what the transfer requires. On a 2021–2022 car this is often three to four years of cover still running, and it is a large part of what you are buying. |
| Measure it yourself if you can | An OBD2 adapter with a supported profile costs less than a tank of fuel and gives you a number in the driveway. Confirm your exact model and year is supported first. |
| Pay for an independent test on anything marginal | Out of warranty, undocumented history, ex-fleet, or a price that seems too good — that is when $250 to $300 buys certainty. Sydney and Canberra have the NRMA option; elsewhere, ask what a local EV-capable workshop can produce and what test it runs. |
| Use the number to negotiate, not just to walk | A five-year-old car at 86 per cent is not a bad car; it is a car with a documented 14 per cent less range than new, and that is a priceable fact. The seller who provided the report has given you the argument. |
| Prefer a dealer if the discount is thin | A private sale strips the statutory warranty and the consumer guarantees. If the private price is only a little cheaper, the dealer purchase is carrying protection the private one is not. |
What we could not establish
Four things. We could not verify the coverage or pricing of chain-workshop battery testing in Australia — mycar advertises an EV battery health test, but its page returned an access error to us and we are not repeating figures we could not read. We could not find published Australian data on the actual distribution of SoH across used EVs sold here, so the Geotab rates are a global fleet average applied to an Australian market, not a local measurement. We could not confirm how Victoria’s statutory-warranty exclusion of “batteries” is applied to traction packs. And out-of-warranty replacement costs vary so widely by pack size, brand and repairability that the $6,000 to $20,000 range is a rough envelope rather than a quote — module-level repair, where a brand supports it, can cost a fraction of a full pack.
The bottom line
The used EV market in Australia has become genuinely cheap, and the data says the batteries in it are mostly fine — better than the folklore, and comfortably inside their warranted life at average degradation rates. That is the good news, and it is the reason a used EV is now a sensible purchase rather than a gamble.
What has not caught up is disclosure. A used petrol car tells you most of what it is through its odometer and its service book. A used EV does not, because the expensive part of it keeps its condition to itself. Until an SoH figure is a standard line on a listing here, the whole gap between a bargain and an expensive mistake sits in one number that costs $250 to $300 to obtain, or nothing at all if the car and the app agree to talk to each other.
Get the number. Then negotiate.
Sources
Figures, terms and quotes above are drawn from these sources, captured 17 August 2026:
- Geotab — EV battery health: key findings from 22,700 vehicles (28 April 2026): the 2.3 per cent average annual degradation rate, 81.6 per cent projected state of health at eight years, the sample of more than 22,700 vehicles across 21 models, and the DC fast-charging breakdown of 1.5, 2.2 and 3.0 per cent a year by charging frequency and power.
- NRMA Open Road — Used EV sales surge as buyers turn electric (20 July 2026): the AADA, AutoGrab and Pickles report showing used EV sales up 54.6 per cent year on year in H1 2026, PHEVs up 468.4 per cent, electrified vehicles at 7.1 per cent of the used market, Pickles average prices of $35,500 in January, $41,500 in April and $31,500 in June, and average selling time falling from over 60 days to under 40.
- NRMA — EV Battery Health Check: the Aviloo partnership, the score out of 100 and capacity report emailed to the customer, $250 member and $300 non-member pricing, Sydney metro and Canberra availability, weekday hours and two days’ booking notice, coverage of over 90 per cent of BEVs and PHEVs, exclusion of conventional hybrids, and the caveat on replaced or refurbished batteries.
- Aviloo — battery diagnostics: the FLASH test at about three minutes with machine-learning inference trained on prior full tests and quoted accuracy of roughly ±3 per cent against the PREMIUM test, and the PREMIUM test’s full-discharge-cycle analysis covering state of health, range, cell-level voltages and battery management system checks.
- EV Central — It is a buyer’s market: used EV prices plunge as more models arrive (20 March 2026): broker Savvy’s analysis of RedBook data putting a 2022 Tesla Model Y rear-drive about 48 per cent below its original price and a BYD Atto 3 about 39 per cent below.
- NSW Government — Dealer guarantees and warranties: the three months or 5,000km dealer guarantee, the under-ten-years and under-160,000km eligibility limits, exclusions for misuse and auction sales, and the Australian Consumer Law guarantees that apply alongside.
- Consumer Affairs Victoria — Warranties on used cars: Victoria’s three months or 5,000km statutory warranty, the ten-year and 160,000km limits, the exclusion list including batteries, the trader’s repair and towing obligations, and the statement that the warranty does not transfer on a private sale.
- Queensland Government — Guarantees and warranties for second-hand vehicles: the Class A warranty of three months or 5,000km for vehicles under ten years and 160,000km, and the Class B warranty of one month or 1,000km for older or higher-kilometre vehicles.
- CarsGuide — Electric car battery warranties explained and Cars24 — Best EV battery warranties in Australia 2026: the prevailing eight-year/160,000km terms with a roughly 70 per cent capacity retention floor, MG’s ten-year/250,000km battery warranty, and Kia’s shorter seven-year term.
- NRMA — How much does it cost to replace an EV battery? and Compare the Market — EV battery replacement cost index: the roughly $6,000 to $20,000 Australian out-of-warranty replacement range depending on pack size, and the finding that Australian replacement costs are comparatively low internationally.
- Zedmotive — How to check a used EV’s battery health with OBD2 and OBDadvisor — Car Scanner ELM OBD2 review: the driveway OBD2 method, Car Scanner’s connection profiles and community parameter IDs across brands, the limits of generic OBD2 mode, model-by-model coverage variation, Tesla’s Service Mode battery health report, and third-party access breaking after Tesla software updates. Commercial and enthusiast sources, cited here for method rather than for any figure.