The most common mistake is treating the dash range estimate as a health figure. It is calculated from recent driving efficiency and it moves with the weather, your right foot and the last few trips. A week of gentle commuting in mild conditions can lift it noticeably without a single cell improving.
Why Tesla battery health is harder to read than it looks
Standard-range and rear-drive Teslas generally use lithium iron phosphate cells. LFP is durable, tolerates daily charging to 100% and handles Queensland heat better than the alternative — but it has a very flat voltage curve. That flatness is exactly what defeats estimation-based tools, including most phone apps: with so little voltage movement across the middle of the pack's range, there is almost nothing for an estimate to work from.
Long Range and Performance cars use nickel-based chemistry, which does show a usable voltage curve, and which is more sensitive to sustained heat and to sitting at high states of charge. Different chemistry, different ageing pattern, different advice — and a different reading method.
What a proper check produces
Four things, all read from the vehicle rather than inferred from it.
Usable capacity
What the pack actually holds now, against what it held when it left the factory. This is the headline number and the one that moves a price.
Cell voltage spread
How evenly the cells sit relative to one another. A pack can show acceptable total capacity while a single weak module drags on every charge — the spread is what exposes it.
Charge history and cycle mix
The balance of AC and DC charging over the car's life, and the cycle count. This is what separates a garaged private car from an ex-rideshare vehicle with a similar odometer.
Thermal and fault history
Stored fault codes, thermal events and any evidence of previous high-voltage work — the context that tells you whether a number is wear or a symptom.
When the reading can mislead
Two situations produce a number we have to caveat, and an honest report says so. A pack sitting at 100%, or one that has been parked for a fortnight, will not read cleanly. Nor will a car whose battery management system has recently been reset — clear the modules and the pack reports optimistically until it has relearned over a few hundred kilometres.
We ask sellers to have the car at around half charge for exactly this reason, and where conditions are not ideal we say what was and was not reliably tested rather than quietly rounding.
Buying, selling, or just want to know
Most of these checks are done for buyers, as part of a Tesla pre-purchase inspection. They are just as useful the other way round: a documented state of health figure with the VIN on it is the strongest thing a private seller can put in a listing, and it removes the argument before it starts.
For the general method across all makes, see how state of health is tested and what degradation is normal for a car's age.
Tesla battery questions
Can an app check Tesla battery health?
Only partly, and not reliably on LFP cars. Apps that estimate capacity from voltage struggle badly with the flat LFP curve used in standard-range and rear-drive Teslas. A diagnostic read from the battery management system is the sound method on any chemistry.
What is a good state of health for a used Tesla?
It depends on age, kilometres, chemistry and how the car has been charged, so a single threshold is misleading. What matters is whether the figure is reasonable for that specific variant and age, and whether the cell spread is even — a low reading with a wide spread is a different problem to gradual, even wear.
Does the Tesla range display show battery health?
No. It is a prediction based on recent driving efficiency and it changes with temperature, driving style and the last few trips. It is a useful comfort signal for an owner and close to useless as a purchase decision.
Is Tesla battery degradation covered by warranty?
Tesla covers the battery and drive unit for 8 years or 160,000 km on rear-drive cars, and 8 years or 192,000 km on Long Range and Performance variants, with a minimum 70% capacity retention over that period. Gradual loss above that floor is normally excluded, while a genuine defect is covered.
Get the real number, with the VIN on it.
Read from the car, reported in writing, anywhere in Brisbane, Sydney or Melbourne.