Nobody buying a used EV lies awake worrying about a percentage. They worry about whether the car will get them to work all week, or to the coast and back, without a stressful stop at a charger that might be broken.
So this guide is really about one question — how far will this particular car actually go? — and battery health is simply the only honest way to answer it.
Why the two numbers you are given are both useless
When you look at a used EV listing, you are typically offered two range figures, and neither one tells you what you need.
The brochure range is the manufacturer's original lab figure, measured under a standard test cycle when the car was new. It does not account for the capacity the battery has lost since, and lab cycles are gentler than a real commute — no headwind, no hills, no air conditioning fighting a 38-degree afternoon.
The dashboard estimate is worse, because it looks authoritative. Most EVs calculate that number from recent driving. A car that has spent a fortnight doing gentle suburban trips will flatter itself; the same car after a week of highway running will read lower. Sellers quote whichever number the car happened to be showing.
A tired battery and a fresh one look identical in a photograph, and often display a similar dashboard estimate. The difference only shows up when you measure it — or three months later, when you are the one stopping to charge.
Turning battery health into actual kilometres
This is the step almost everyone skips. A state-of-health figure on its own is trivia; what matters is what it does to your driving.
The arithmetic is simple. If a car left the factory with a 400 km rating and the battery now measures 88% state of health, its realistic full charge is roughly 350 km under the same conditions the original figure assumed. Then you apply reality: highway speeds, climate control, hills, a roof box, cold mornings. Depending on how and where you drive, that can take another 10–25% off.
Which leaves the only question that matters: is what remains comfortably more than your actual week? For most people the honest answer is yes, with room to spare — and they were about to spend thousands extra on range they would never use.
This is also why we ask how far you drive before we talk about cars at all. “Enough range” is not a property of the car. It is a relationship between the car and your life.
What “state of health” actually means
State of health (SOH) is the battery's current usable capacity expressed as a percentage of the capacity it had when new. A pack showing 92% SOH will hold roughly 92% of the energy it originally did, which translates fairly directly into 92% of the original driving range.
It is not the same thing as state of charge, which is simply how full the battery is right now — the equivalent of a fuel gauge. A car can show 100% state of charge and 84% state of health at the same time. Sellers occasionally conflate the two, sometimes innocently.
How much degradation is normal
Batteries lose capacity fastest in their first year or two and then settle into a slow, fairly predictable decline. The shape of that curve matters: a three-year-old car that has already dropped a few per cent is usually behaving exactly as expected, not failing.
What is not normal is a sharp drop, a pack that is well out of step with others of the same age and mileage, or a battery management system reporting faults. Those are the cases worth walking away from, and they are the reason we ask for a measured figure rather than a reassuring sentence.
Degradation also depends on chemistry. Most newer, more affordable EVs sold in Australia use lithium iron phosphate (LFP) packs, which tolerate being charged to 100% routinely and tend to age well. Longer-range models more often use nickel-based (NMC) chemistry, which prefers to live between roughly 20% and 80% for daily use. Advice written for one chemistry is actively wrong for the other, which is why generic “never charge to full” advice should be ignored until you know what is in the car.
How battery health is measured
There are two broad approaches, and the difference between them matters.
1. An on-board diagnostics (OBD) reading
A tool plugs into the car's diagnostic port and reads what the battery management system believes the capacity to be. It takes minutes and it is inexpensive. The limitation is that it reports the car's own estimate, which can drift, can be skewed by a recent charge or a long period parked, and does not test how the pack behaves under load. It is a useful screen, not a verdict.
2. A full charge/discharge test
The pack is measured across a controlled charge or discharge cycle, which produces a far more reliable capacity figure and can also surface cell imbalance — where individual cells in the pack have drifted apart, which is an early warning sign that an averaged number will hide. It takes longer and costs more. It is the closest thing to a definitive answer.
Several independent providers now offer battery testing in Australia, including mobile services that come to the car. If you are buying privately, commissioning your own test is money well spent on a purchase this size.
The single most useful question you can ask a used EV seller is: “Do you have a battery health report, and who produced it?” The answer tells you about the car and about the seller.
What a good battery report contains
- State of health as a percentage, with the date and odometer reading it was taken at.
- Who performed the test and how — an OBD snapshot and a full cycle test are not equivalent, and the report should say which it is.
- Cell balance or module-level data where the test supports it, since an averaged figure can conceal a weak module.
- Any stored battery or drivetrain fault codes, including historical ones that have been cleared.
The battery warranty is half the picture
Most electric cars sold in Australia carry a separate battery warranty, commonly in the region of eight years or 160,000 km, whichever comes first, with the manufacturer undertaking to repair or replace the pack if capacity falls below a stated threshold — typically around 70%. That warranty is often the single most valuable thing attached to a used EV.
Two details decide whether it is worth anything to you:
- How much of it is left, in both years and kilometres. A car three years into an eight-year term still has real protection.
- Whether it transfers to you as the second owner. Terms vary by manufacturer, and a warranty that ends with the first owner is worth nothing to a used buyer. Confirm this in writing for the specific model and build year before you commit — do not rely on a general claim about the brand.
A pack sitting just above the warranty threshold is a different proposition from one sitting comfortably above it, and the price should reflect that.
Questions to ask before you inspect
- Is there a battery health report, and may I see it before I visit?
- What is the state of health, and at what odometer reading?
- How much of the battery warranty remains, and does it transfer to me?
- Has the car been DC fast-charged as a matter of routine, or mostly charged at home?
- Have any battery modules or the pack been repaired or replaced?
- May I commission my own independent battery test?
A seller who is relaxed about that last question is usually a seller with nothing to hide. Hesitation there tells you more than any number will.
Warning signs
- No report, and reluctance to allow one. On a purchase this size that is disqualifying, not inconvenient.
- A quoted range that comes from the car's dashboard estimate rather than a test. That figure reflects recent driving, not capacity.
- Warranty history that has been “lost”, or a service record with unexplained gaps around drivetrain work.
- A price that is well under the market for the model. On EVs that is frequently a battery story.
Where this leaves you
Real range is knowable. It is not a mystery and it is not a matter of opinion — it is a measurement plus some arithmetic. Any seller treating that as an awkward question is telling you something.
If you would rather not do this yourself, tell us how you drive. We search the whole market — listed cars, trade-network stock before it is advertised, and the ex-fleet and ex-novated-lease EVs coming off contract — and every car we put in front of you is battery tested, given a 120-point safety check and covered by warranty.
One of the places we look is EV Depot, which is owned by the same people as EVFinder. We would rather say that outright than have you wonder — and if the better car is somewhere else, that is the one you will hear about.
General information only. Battery performance, degradation and warranty terms vary by manufacturer, model, build year, climate and how the car has been used. Always confirm warranty terms in writing for the specific vehicle before purchasing.