Four different things are sold in Australia under roughly the same promise. They are not equivalent, and the differences are not explained anywhere — so here they are, including where the test we perform is the weaker option.
1. The car's own dashboard estimate — free, and not a measurement
Every EV shows a range estimate and a charge percentage. Neither is battery health.
The range figure is a prediction built from recent driving efficiency. Drive gently for a week and it rises. Drive fast in winter with the heater on and it falls. The battery did not change. Two identical cars with identical packs can show ranges 40 km apart on the same morning.
The charge percentage tells you how full the battery is, not how large it still is.
What it's good for: nothing, as far as assessing a used car goes. A seller showing you a full-charge range figure is showing you their recent driving style.
2. A generic OBD2 scan — cheap, shallow
Plug a consumer scan tool into the diagnostic port and you can read fault codes and, on some models, a manufacturer-reported health figure.
What it's good for: finding stored fault codes, and confirming a car is not hiding an obvious problem.
Where it stops: coverage varies enormously by make. Many EVs do not expose a meaningful health figure over generic OBD2 at all, and most consumer tools cannot read individual cell voltages — which is where a developing problem shows first. You get a number, or you get nothing, and you rarely get the detail behind it.
3. A quick diagnostic read — what we do
A professional battery diagnostic reads the battery management system's own State of Health and cell-level data, analyses it against the pack's factory specification, and produces a written, certified result. It takes minutes, the car does not move, and nothing is written to the vehicle.
What it's good for: a specific, documented, independently verifiable figure — including cell voltage spread, which a single health number hides and which is the earliest indicator of an unevenly ageing pack. It can be done in a seller's driveway on a Saturday, which is when and where used cars are actually bought. The result is a certificate a buyer can check independently.
Here is where it is weaker, and we would rather you heard it from us. This method reads and interprets the vehicle's own battery management data. It is not an independent physical capacity measurement — it does not charge and discharge the pack to measure what comes out. Under the CARA Europe battery health scheme, this is the category of test that reads State of Health from the vehicle's own systems without stressing the battery, as distinct from a premium test that produces a result independent of manufacturer data.
That distinction is real and we are not going to blur it. What we would say in its defence: the battery management system's internal health figure and its cell-level data are an entirely different order of information from the range estimate a driver sees, they are what the manufacturer itself uses, and they are what the warranty is ultimately assessed against.
4. A full charge-and-discharge test — the most thorough, and the least practical
An external test that charges, discharges or drives the vehicle through a controlled cycle, measuring what the pack actually delivers rather than what it reports.
What it's good for: the most complete answer available. Independent of the manufacturer's own reporting.
Where it stops: time and access. A test of this kind is measured in hours or days, not minutes. The vehicle has to be available for the duration and driven or cycled under controlled conditions. No private seller is going to hand you their car for two days so you can decide whether to buy it, and on a car you already own it means being without it.
It is the right test for a fleet assessing its own vehicles, a dealer preparing stock, or an owner with a specific dispute. It is rarely the right test for a pre-purchase decision on somebody else's car.
How to choose
| Your situation | The sensible option |
|---|---|
| Buying privately, seller wants a decision today | Quick diagnostic read |
| Buying at auction, limited access, hard deadline | Quick diagnostic read |
| You own the car and suspect a specific fault | Quick diagnostic read first; full cycle test if the result is ambiguous |
| Preparing to sell and want documented evidence | Quick diagnostic read, for the certificate |
| Disputing a warranty claim with a manufacturer | Start with a documented diagnostic read; a full cycle test may be needed |
| Assessing a fleet you already control | Full cycle test, where time allows |
| Curious, spending nothing | The dashboard — but understand it tells you almost nothing |
Why we published this
Because the comparison did not exist, and because a customer who understands the limits of what they bought is a better customer than one who does not.
We would rather you book the right test — even when that is not ours — than book ours believing it does something it does not.
Book a test — $249 · What State of Health is normal
Test-category definitions from CARA Europe's Battery Health Check scheme, the independent European certification body whose approved-provider list includes TÜV NORD, DEKRA, Autel, MAHLE and AVILOO. Verified 13 September 2026.