"The battery will need replacing after eight years" is one of the most commonly cited reasons people give for not buying a used electric car. The data does not support it, and the data is now substantial.
What the degradation data actually shows
Geotab analysed more than 22,700 electric vehicles across 21 models. The headline finding: average degradation of 2.3% per year, which projects to 81.6% of original capacity at eight years.
Two things follow from that. First, an eight-year-old EV has lost roughly a fifth of its range, not all of it. Second, the loss is gradual rather than a cliff: Geotab found many EVs show a sharper drop in the first year or two before the rate levels out, and eight of the eleven established models it re-measured had stabilised to about 1.4% a year. Outright pack failures do happen, but they are rare and separate from this gradual fade — see the replacement figures below.
Geotab's own conclusion on lifespan: around 13 years or more based on observed rates. The Australian Government's position is similar — many EV batteries last up to 15 to 20 years or 200,000+ km before significant degradation.
Charging habits matter more than age
This is the most useful part of the dataset for someone buying second-hand.
Projected capacity at 8 years, by charging habit
- Mostly low-power charging
- 88%
- Fleet average
- 81.6%
- Frequent DC fast charging
- 76%
Cars charged mostly at low power degrade about 1.5% a year. Cars frequently using high-power DC fast charging above 100 kW degrade about 3.0% a year. Hot climates add roughly 0.4% a year — directly relevant in Australia.
So the question to ask a seller is not just how old the car is, but how it was charged. An ex-fleet or ex-rideshare EV that lived on fast chargers is a different proposition from a home-charged private car with the same odometer.
One myth Geotab actively debunks: the 20–80% rule is not critical for daily use. Degradation only accelerated when a car spent over 80% of its total time at extreme states of charge. Low-exposure and medium-exposure groups were near-identical.
How often are batteries actually replaced?
Rarely, and increasingly rarely.
Recurrent Auto, working from more than 30,000 connected vehicles, found that outside the major recalls under 4% of EVs across all years and models have had a battery replaced — including cars more than ten years old. Broken down by generation: first-generation EVs around 8.5%, second-generation around 2%, and modern EVs from 2022 onwards, 0.3%.
That is US data from a self-selected connected-car community, and Recurrent says so, so treat it as indicative rather than exact. But the direction is unambiguous and consistent with the degradation data.
Australian data agrees. Pickles tested more than 1,500 EVs and found an average state of health of 96%, with cars beyond 120,000 km still retaining about 90%. Splend’s rideshare fleet — high-mileage cars, so a conservative test — reported 94–95% averages across hundreds of Polestar 2, Model 3 and Model Y.
One honest tension worth noting: Pickles compared 800+ EVs at opposite ends of DC-charging reliance and found a lifetime difference of about two percentage points, much smaller than Geotab’s annual-rate finding. The two measure different things — sustained high-power fleet duty against a mixed consumer population — and both are well sourced.
What the warranties guarantee
New EVs typically carry a separate high-voltage battery warranty of around 8 years and/or 160,000 km, sometimes with a guarantee that the battery retains above a stated proportion of original capacity.
⚠ Do not assume a 70% floor, despite how often it is repeated. Of the Australian manufacturer pages checked, Toyota states 70% for the bZ4X, BYD guarantees at least 70% capacity retention over its 8 years / 160,000 km traction-battery term, and Nissan expresses it as bars on a gauge, while MG and Hyundai state no percentage on their own warranty pages at all. Read the specific brand’s terms rather than a comparison table.
Manufacturer terms in Australia, from their own warranty pages:
- Hyundai — high-voltage battery 8 years / 160,000 km. The balance of warranty transfers to a new owner.
- BYD — traction battery 8 years / 160,000 km with a guarantee of at least 70% capacity retention; vehicle warranty 6 years / 150,000 km.
- MG — high-voltage battery 7 years / 150,000 km. ⚠ This is not the same thing as MG’s headline vehicle warranty of up to 10 years / 250,000 km, and the two are widely confused — comparison sites routinely quote the vehicle figure as the battery figure. The vehicle warranty’s extended portion separately requires exclusive servicing at an authorised MG dealer within 30 days and 2,000 km of each interval.
- Toyota — traction battery cover is five years standard, extended to ten years only if an annual battery health check and routine logbook maintenance are done at Toyota. ⚠ Read what that cover is: Toyota’s own disclaimer says it excludes traction battery capacity degradation, which is handled separately, and excludes vehicles used commercially — taxis, hire cars and rideshare. For the battery-electric bZ4X, separately, 8 years / 160,000 km if capacity falls below 70% of original, subject to those health checks.
- Nissan — 96 months / 160,000 km, with the capacity guarantee expressed as bars remaining on the car’s own gauge rather than as a percentage.
The pattern is that length is the headline and conditions are the substance. Check what was required, and whether it was done.
How to check state of health before you buy
- The car's own display, where it offers one.
- An OBD2 dongle plus a model-specific app — Leaf Spy, OBD Fusion, Scan My Tesla, CanZE.
- A professional test. The NRMA offers member-discounted battery health checks in Sydney metro and Canberra and partners with Redbook Inspect; mycar offers a report under the name Voltest.
A caution worth carrying: the figure a car reports comes from the manufacturer's own algorithm and can be higher or lower than the pack's real condition. A test that reads individual cell voltages catches imbalance that a single headline number hides.
Rough guide: above 90% excellent, 80–90% normal at three to five years, below 75% significant, and a large spread between cells is a red flag regardless of the headline figure.
The one model-specific caution worth stating
Early Nissan Leaf models use a passively air-cooled battery without active liquid thermal management, which makes them more susceptible to heat-related capacity loss than later designs — a real consideration in the Australian climate. Geotab's confirmed finding that hot climates add degradation supports the concern.
Compounding it: the Leaf uses CHAdeMO, and the NRMA is phasing that connector out of its network. Neither fact rules out a cheap Leaf as a short-range second car, but both belong in the price you pay.
What this means in practice
Buy on measured state of health rather than on age, ask how the car was charged, check that the warranty's servicing conditions were met, and price a first-generation EV differently from a modern one. The full inspection list is in buying a used electric car.