Nothing about buying a second-hand electric car in Australia is more stressful than the battery. Not the price, not the bodywork, not the mileage — the battery. Because if the battery is hiding a problem, you won't find out until months after the handover, when it's far too late.
Here's the truth: most of the traps in the used-EV market are hidden in battery data that most buyers can't read. This guide breaks it down in plain English: the two chemistries you need to know, the five numbers that tell the truth, and a complete inspection routine — even for first-time buyers.
Two battery chemistries, two very different weaknesses
Every mainstream battery electric car on the market uses one of two chemistries, and their weaknesses are completely different:
LFP (lithium iron phosphate) is the workhorse: durable, thermally safe, and built to last hundreds of thousands of kilometres. Its one real weakness is the cold — range drops noticeably in winter, which is normal physics, not a sign of a failing battery.
NMC (nickel manganese cobalt) delivers steadier range and better cold-weather performance for long-range electric cars, but it's less forgiving. Frequent fast charging and aggressive driving accelerate degradation noticeably.
The key takeaway: a shorter winter range in an LFP vehicle is not battery degradation. Don't let a seller use it to talk the price down — and don't mistake it for a vehicle fault.
Why battery degradation can't be "fixed"
Some sellers claim battery degradation can be "rebalanced" or "restored to full health". That's simply not true.
Lithium-ion degradation is permanent physical ageing inside the cells. Software rebalancing or data "refreshing" can only polish the numbers on a screen — it does nothing for real range or real battery life.
Don't trust the screen: the dashboard can lie
Here's one of the biggest mistakes used-EV buyers make: checking the state of health (SOH) readout on the car's display and taking it at face value.
That display is the output of the battery management system (BMS). With the right equipment, sellers can optimise, adjust or even rewrite it. An old, worn battery can be made to display a healthy SOH. The screen can lie. The official battery report, drawn from the manufacturer's records, cannot.
The 5 numbers that tell the truth
When you get a battery report, you don't need to understand every line. Focus on these five indicators:
1. SOH — the battery's remaining life
SOH compares the traction battery's current capacity with its capacity when new. The higher, the better:
Above 90%: excellent condition, almost no degradation, range close to new — buy with confidence.
85–90%: normal household wear; a good used EV, buy if the price is right.
80–85%: noticeable degradation; fine for daily commuting, but expect more winter range loss — negotiate hard.
Below 80%: severely aged. The 80% benchmark is widely treated as the battery-replacement threshold — walk away, because you'll likely be paying for a new pack yourself.
2. Charge cycles — how hard the battery has worked
One full charge-and-discharge cycle counts as one cycle. The more cycles, the more the battery has aged.
A typical household car completes about 100–300 cycles per year. If a three-year-old car shows more than 800 cycles, treat it as a red flag. It has almost certainly been used as a ride-share or commercial vehicle — heavy charging and high mileage wear the battery far beyond what the SOH figure suggests.
3. Cell voltage difference — the hidden fault
A battery pack is made up of hundreds of individual cells. The voltage difference between cells reflects how consistent the pack is:
Within 50 mV: healthy — stable range, no surprises.
50–100 mV: mild imbalance — occasional range drops, slower charging.
Above 100 mV: serious — erratic range, charging interruptions, and a long-term thermal risk.
Here's the warning experienced buyers know: voltage difference matters more than SOH. A car can show a high SOH while its cells are badly imbalanced — and that's still a problem for the battery.
4. Fast-charge ratio — the aging accelerator
Fast charging is like binge eating: convenient, but it ages the battery faster. If more than 70% of the vehicle's charging history is DC fast charging, the battery has accumulated hidden stress. It will degrade faster than a car that is mostly slow-charged. Be cautious.
5. Fault records — the deal-breaker
If the report shows any of the following, walk away regardless of the price:
Battery pack water ingress or collision repair
Cell damage
Insulation faults
Thermal events
Voltage-difference faults
Forced shutdown records
A battery is a sealed, precision component. Once it has been repaired, flooded or damaged, it carries a lifetime risk that no discount can justify.
A complete used-EV inspection in 3 steps
Reading the report is only half the job. A thorough inspection combines online data with physical testing — two layers of checks, zero blind spots.
Step 1: Pull the official battery report
The fastest, cheapest way to start is to look up the vehicle's official battery report using its 17-character VIN (found on the registration document or the door pillar). In seconds, you can check SOH, cycle count, cell voltage difference, fast-charge ratio, fault records, service history and previous registrations. It's a full sweep that works for any brand of EV — without the seller's involvement.
Step 2: Three on-site tests
Charge to 100% and let it rest for 1–2 hours. If the range drops by several kilometres while the car is parked and off, the cells are imbalanced or ageing — a sign of overstated range.
Charge from 30% to 80%. On a healthy EV, fast charging should be smooth. Frequent interruptions, inconsistent speeds or charging that stops and restarts point to an internal problem.
Drive a few kilometres at both low and high speed. Watch whether the range decreases in a linear, predictable way. A sudden cliff-edge drop is a deal-breaker.
Step 3: Watch for three problem profiles
High-cycle vehicles with commercial history: even with clean-looking data, wear far exceeds a private car.
Repaired, flooded or crashed batteries: no warranty on the three electric components, and a serious safety risk.
High SOH but high cell voltage difference: a hidden fault with expensive repair bills later.
The bottom line
Screen data is not trustworthy — the official report is the truth. SOH alone is a trap — check voltage difference and cycles too. Frequent fast charging damages batteries, and repair-or-flood histories are a permanent risk. Check online, test on-site, and you can buy with confidence.
Ready to start with a battery that's built to last? Book a test drive with XPENG and see how a genuinely durable battery performs in one of Australia's best electric cars.
Note: Battery figures and thresholds refer to general industry guidance. Actual battery condition varies with usage, climate and maintenance.
