How to Check Used EV Battery Health Before You Buy (Australia)

Battery health is the single most important check on a used EV
Image courtesy of Tesla, Inc. Source: tesla.com/en_au/tesla-gallery

The single number that decides whether a used EV is worth buying is its battery State of Health, or SOH. The odometer matters less than you think. Two examples of the same Model 3 with the same kilometres can have wildly different real ranges, and the only way to know which is which is to run a proper battery health check. Here’s how to do that in Australia, what counts as acceptable, and what to do if the seller refuses.

What “battery health” actually means

State of Health (SOH) is the percentage of the battery’s original usable capacity that remains. A new EV is 100%. A 5-year-old car typically sits somewhere between 88 and 94%. SOH translates directly to real-world range: a car with 85% SOH will go 85% as far as new, all else equal.

SOH is not the same as State of Charge (SOC), which is just how full the battery is right now. The dashboard shows you SOC. SOH is hidden inside the battery management system and needs a tool to read.

Battery degradation is normal and unavoidable. What you’re checking is whether this specific car has degraded faster than its peers. The usual culprits are a fault, abuse (constant DC fast charging, frequent 100% charges, hot climate) or plain bad luck with cell variation.

What’s an acceptable SOH for the age?

Rough guide for cars with normal use:

  • 1 to 2 years old: 96 to 99%. Anything below 95% is suspicious.
  • 3 to 4 years old: 92 to 96%. Below 90% is a yellow flag.
  • 5 to 6 years old: 88 to 93%. Below 85% means significant range loss.
  • 7+ years old: 80 to 88%. Below 78%, walk away unless the car is heavily discounted.

Different chemistries age differently. Geotab’s analysis of fleet EVs found average degradation of around 1.8% per year, though with significant variation by model, climate and charging habits. LFP chemistry (BYD Atto 3, MG4, Tesla Model 3 RWD post-2021) ages more slowly than NCM/NMC, and tolerates 100% daily charging better.

The four ways to actually check it

1. The car’s own diagnostics (free, partial)

Tesla shows you nothing useful through the touchscreen, so you have to infer SOH from the rated range at 100% charge. Hyundai and Kia don’t expose it directly either. BYD and MG show partial info in service menus. The Nissan Leaf is the exception: owners can pair the free LeafSpy app with a $20 OBD dongle and get accurate per-cell SOH data on a phone.

For everything else, you need a tool.

2. A consumer OBD reader and app ($50 to $150 all up)

An OBD2 dongle plus the right app shows you the same numbers a workshop sees. The catch is that “the right app” is different for every brand, and one of them (Tesla) doesn’t even have a normal OBD2 port.

Nissan Leaf. Still the easiest EV in Australia to check yourself. LeafSpy Pro costs $29.99 on the Australian App Store, covers 2011 to 2025 Leafs, and shows the voltage of all 96 cell pairs plus the battery AHr rating, which is the figure that falls as capacity goes. It needs a supported Bluetooth 4+ LE adapter, and the developer names the Vgate vLinker FD+ and MC+. Spend an hour learning to read it and you’ll know more about a Leaf’s battery than the person selling it. Worth doing alongside our used Nissan Leaf buyer’s guide.

Hyundai and Kia. Car Scanner ELM OBD2 reads State of Health straight off the Kona Electric’s battery management system: one documented test returned 97.1% SOH and roughly 62kWh of usable capacity. The same app handles the Ioniq 5, Ioniq 6 and EV6 with any decent Bluetooth adapter. The more useful trick is that these packs log cumulative DC fast-charge energy and cumulative AC charge energy as separate counters, so you can see how much of the car’s life was spent on a fast charger instead of taking the seller’s word for it.

Tesla. The hardest of the lot. There’s no standard OBD2 port, so you need a model-specific adapter harness plus a compatible OBD2 adapter (a vLinker FS or an OBDLink MX+) before the Scan My Tesla app will show you anything. Tesla’s own in-car test used to fill the gap, under Controls, then Service, then Battery Health. Don’t count on it: Tesla quietly pulled the test from many cars in software update 2025.26 and removed the on-demand version from Service Mode, so whether the button exists depends on model, build year and whether a test has been run before.

BYD, MG and everything else. Coverage is patchy and shifts with firmware. Treat a DIY reading on these as a bonus rather than a plan.

Our take: the dongle route is excellent if you already own the car and want to track it over the years. As a buying tool it’s awkward, because you’re asking a stranger to let you plug hardware into their car and sit in it for twenty minutes. Inspecting three or four cars, it pays for itself. Inspecting one, pay for a certificate instead.

3. An independent battery health certificate ($150 to $300)

This is what we’d actually do, and prices have dropped a long way. The Aviloo Flash Test has become the default in Australia: it plugs into the OBD port, takes about three minutes with no driving required, works on more than 95% of plug-in vehicles, and starts at $200 through the Australian and New Zealand distributor. Results are benchmarked against a database of over 500,000 previous tests, which matters more than the raw percentage because it tells you whether this car is normal for its model and age.

Where to get one, at time of writing:

The certificate is worth more than the number printed on it. It’s dated, independent and transferable, so it works as a negotiating document now and again when you sell. Manheim’s numbers make the point: it began offering Aviloo certificates on consigned EVs in September 2025 after seeing that, in its German operation, certified cars cleared 15% more often and drew 22% more bids. And carsales research found 59% of prospective buyers name battery condition as their biggest hesitation on a used EV. A piece of paper removes the objection.

4. Manufacturer dealer scan ($0 to $200)

The dealer for the brand can run the manufacturer’s proprietary diagnostic. Coverage is mixed. Some dealers will do it free as part of a pre-purchase inspection (Hyundai and Kia tend to be cooperative), while others, Tesla service centres especially, won’t engage unless you own the car. Worth asking but don’t rely on it.

What SOH number should make you walk away

Start with 70%. That’s the floor almost every manufacturer guarantees, typically for eight years or 160,000km, whichever comes first. It matters because it splits the risk cleanly. A pack that drops below 70% inside that window is the manufacturer’s problem. A pack sitting at 72% just outside it is entirely yours.

Then judge the number against kilometres, not just years. RACV cites Australian auction data showing EVs between 80,000 and 120,000km averaged 91% State of Health, while cars past 120,000km averaged 83%. Against that backdrop, here’s where we’d draw the lines:

  • Below 90% on a car under five years old: walk, unless the discount is big enough that you’d still be happy if it kept falling.
  • More than five points below comparable cars of the same model and mileage: walk. A gap that size is usually a fault or hard use, not chemistry.
  • Below 80% on a car you intend to keep five years: walk. At the fleet-average rate of 2.3% capacity loss per year across 22,700 vehicles, you’re heading for the warranty floor in a car that has no warranty left.
  • Between 85 and 90% on a high-kilometre car: negotiate, don’t walk. That’s roughly normal, and it’s still worth real money off the asking price.

What the percentage won’t tell you is how fast it will keep falling. Geotab found that vehicles relying on DC fast charging above 100kW degraded at 3.0% a year against 1.5% for cars charged mostly at low power, which projects out to 76% versus 88% capacity after eight years. An ex-fleet or rideshare car sitting at 90% today is not the same asset as a home-charged car sitting at 90% today, and you should price it accordingly. We go deeper into how the curves behave by model in EV battery degradation in Australia, and if you’re trying to work out whether an asking price already reflects a tired pack, start with used EV prices in 2026.

The on-the-day checklist

If you can’t get a proper test before purchase, do this minimum before handing over money:

  1. Charge to 100% before viewing. Ask the seller to do this. Note the rated range shown and compare it to the new-car spec.
  2. Drive at least 30 km on a mix of speeds. Watch the consumption rate (Wh/km or kWh/100km). High consumption with no headwind or cold weather means the battery isn’t delivering rated capacity.
  3. Check the charging history if possible. Tesla’s onboard log, the Hyundai/Kia app, or service records will show how often it’s been DC fast-charged. Heavy DC use accelerates degradation.
  4. Look for warranty transfer. Most EV battery warranties are 8 years/160,000 km and transferable, but only if the previous owner serviced through authorised channels. Ask for the service log.
  5. Cold morning test (if possible). Battery degradation shows up most in cold-weather range. A test drive on a 5°C morning tells you more than a 25°C afternoon.

Red flags that mean walk away

  • Seller refuses any battery diagnostic, full stop
  • SOH below 85% on a car under 5 years old
  • Cell voltage spread over 50mV under load
  • Any active battery-related fault codes
  • Rated range at 100% charge more than 15% below new-car spec
  • “It’s been mostly DC fast-charged”, which is common in ex-fleet and Uber cars
  • No service history with the manufacturer (warranty may already be void)

Buying a hybrid instead? The inspection is a different job

A Prius, Camry Hybrid or RAV4 Hybrid isn’t an EV, and most of the testing services above won’t touch one. NRMA’s check, for instance, covers electric and plug-in hybrid vehicles but excludes conventional hybrids.

For a Toyota, the service book is the inspection. Toyota Australia covers the hybrid battery for five years, then extends it twelve months at a time up to a maximum of ten years, but only if the car is presented to a Toyota dealer for an annual Hybrid Health Check, and the extension doesn’t apply to taxis, hire cars or rideshare vehicles. So when you ask for the logbook on a used hybrid, what you’re really checking is whether five years of battery cover still exists. One missed year ends it for good.

For an independent read, RACT tests hybrid batteries as well as EVs at its Tasmanian workshops. Infinitev runs a free online hybrid battery health check that takes about 90 seconds and asks about charge retention, voltage consistency and cooling fan behaviour. It’s a screening tool rather than a diagnosis, but it’s free and it tells you whether to bother going further.

Keep the downside in perspective. Drive puts replacement of a conventional hybrid pack at $2,000 to $10,000, with plug-in hybrids running $10,000 to $20,000. CarsGuide reports a Camry hybrid pack that costs upwards of $3,000 through Toyota comes in around $2,000 to $2,500 through Infinitev using a remanufactured or aftermarket unit. That’s a bad week rather than a financial disaster, which is why we lose far less sleep over hybrid battery health than EV battery health at similar asking prices.

The $200 that decides the purchase

Spend $200 on a battery health test. It’s the single highest-leverage purchase decision you’ll make on a used EV. If the seller refuses or pressures you to skip it, that is your test result. Walk away.

Most used EVs you look at will have a perfectly healthy pack, and the test just lets you stop worrying and buy the car. On the ones that don’t, you either negotiate the difference or walk before it becomes your problem. Either way the $200 has already done its job, and the certificate stays with the car, so it works for you again the day you sell.

Frequently asked questions

Can a degraded EV battery be repaired or replaced?

Yes, but it’s expensive. Full pack replacement runs $15,000 to $30,000+ depending on the car. Module-level replacement (replacing one bad cell group) is becoming more common in Australia and costs $3,000 to $8,000, though only a handful of specialists do it.

Does fast charging really damage the battery?

Modest, repeated DC fast-charging (a few times a month) has minimal impact on most modern EV batteries. Heavy daily DC use, particularly on older NCM-chemistry packs, does accelerate degradation. LFP packs (Atto 3, MG4) are largely immune.

Is the battery warranty transferable?

On most EVs sold in Australia: yes, the manufacturer’s 8-year/160,000 km battery warranty transfers to subsequent owners, provided the car was serviced through authorised dealers. Always confirm in writing before purchase.

What does an EV health check actually cover?

Two different things get sold under that name. A battery health check reads the battery management system and returns a State of Health percentage, cell voltage data and stored fault codes: NRMA’s version returns a score out of 100 plus current capacity and takes about five minutes. A full EV pre-purchase inspection adds everything you’d check on a petrol car, including brakes, tyres, suspension, panel work and a road test, and RedBook Inspect starts those at $295 with the battery test as an add-on. Buying privately, get both. Buying from a dealer with a statutory warranty, the battery test alone is usually enough.

How much does EV battery testing cost in Australia?

Between $150 and $300 for the test on its own, at time of writing. RACT charges Tasmanian members $150 and non-members $200, EV360 starts at $199, the Aviloo Flash Test starts at $200 through its Australian distributor, and NRMA charges $250 for members and $300 for non-members for a mobile check. Bundled into a full pre-purchase inspection, budget $295 and up. On a $30,000 car that’s under 1% of the purchase price, which is the easiest sum in this article.

Can I check an EV battery myself without a workshop?

On most brands, yes, with a Bluetooth OBD2 adapter and the right app. Nissan Leaf owners have it best: LeafSpy Pro is $29.99 on the Australian App Store and reports every cell pair voltage. Hyundai and Kia owners can read State of Health through Car Scanner ELM OBD2. Tesla is the awkward one, because there’s no standard OBD2 port and you need a model-specific adapter harness first. The one thing you can’t produce yourself is a dated certificate from a neutral third party, and that’s the part that wins arguments about price.

What is a hybrid battery health inspection and do I need one?

On a Toyota it’s a specific thing: an annual Hybrid Health Check at a Toyota dealer that keeps the hybrid battery warranty alive twelve months at a time, up to ten years total. Ask to see it stamped in the logbook before you buy, because a missed year ends the cover permanently. For an independent opinion, RACT tests hybrid batteries and Infinitev offers a free 90-second online screen. Given a conventional hybrid pack runs $2,000 to $10,000 to replace, it’s worth doing on any hybrid past about eight years old.

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