The most common concern about buying a used electric car is whether the battery will still be usable, and the fleet data now available is more reassuring than the early speculation.
How degradation happens
Chemical changes in the cells reducing the charge they can hold.
Which occurs through both use and simple age.
Typical rates
Fleet studies consistently show a few percent in the first year and a slower decline afterwards.
Which produces most packs retaining a large majority of capacity after a decade.
What accelerates it
Frequent rapid charging, sustained high states of charge and heat.
Which are the factors owners can partly control.
Calendar against cycle ageing
Loss from time passing and loss from charge cycles.
Which are separate mechanisms and both are present.
A low-mileage car parked for years still loses capacity.
Thermal management
Systems keeping the pack within a temperature range.
Which is the largest single design factor in long-term durability.
Early vehicles without active cooling degraded noticeably faster in hot climates.
Warranties
Manufacturers typically guarantee a capacity floor over a defined period.
Which sets a baseline expectation and rarely gets claimed.
What degradation feels like
Range reducing gradually rather than the car stopping working.
Which is a very different failure mode from a conventional engine.
Checking a used pack
State of health readings from diagnostic tools.
Which should be part of any used electric vehicle inspection.
Charging habits that help
Avoiding sustained full charge, limiting rapid charging where practical and parking out of extreme heat.
Which are modest adjustments rather than sacrifices.
Many vehicles allow setting a charge limit, and most owners never change it from default.
Buffer capacity
Manufacturers reserve part of the pack that is never used.
Which absorbs early degradation invisibly.
Usable capacity is therefore lower than the headline figure and more stable.
Replacement
Pack replacement costs have fallen and remain substantial.
Which makes remaining capacity a real factor in used pricing.
Module-level repair is increasingly available and reduces the cost considerably.
Second life and recycling
Packs retiring from vehicles retain useful capacity for stationary storage.
Which is developing into an industry and affects residual values.
What the data suggests
Most packs outlast the expectations set a decade ago, and the early failures were mostly specific designs.
What the fleet data shows
Large samples from telematics providers and fleet operators.
Which consistently indicate average annual capacity loss in low single-digit percentages after the first year.
Individual variation is wide, and the outliers get disproportionate attention.
Chemistry differences
Lithium iron phosphate and nickel-based chemistries behave differently.
Which affects both degradation patterns and charging advice.
Iron phosphate packs tolerate regular full charging; nickel-based ones generally prefer a limit.
Software updates
Manufacturers adjusting charging behaviour after delivery.
Which has both improved longevity and, in some cases, reduced usable capacity.
Range in cold weather
Reduced range in low temperatures is not degradation.
Which is a distinction owners frequently conflate.
Cabin heating and cell temperature both contribute, and both recover when it warms.
Buying used with confidence
Request a state of health reading, check the warranty position and ask about charging habits.
A general note
Battery behaviour is model-specific and this is general description rather than guidance for a particular vehicle.
Interpreting a state of health figure
A percentage of original usable capacity.
Which is calculated differently by different tools and by different manufacturers.
Comparing readings across brands is less meaningful than comparing across the same model.
Range estimates in the vehicle
Predicted range based on recent driving.
Which fluctuates with conditions and is not a degradation measure.
Owners frequently misread a cold-weather estimate as capacity loss.
High-mileage examples
Taxi and ride-hailing fleets accumulating very high mileages quickly.
Which provide the best available evidence on long-term durability.
Results have generally been better than the theoretical models predicted.
Insurance and write-offs
Damage to a pack can total a vehicle that is otherwise repairable.
Which has affected insurance pricing and is being addressed through repairability standards.
What owners actually report
The most common observation after several years is that nothing much changed.
Which does not make for compelling coverage and is what the data supports.
The vehicles that failed early were mostly specific designs with known thermal management shortcomings.
The summary
Degradation is gradual, largely predictable, partly manageable through charging habits, and much less severe than early expectations suggested.
Check the state of health before buying used, and otherwise it is not the thing most worth worrying about.
A general note on sources
Figures in this area come from manufacturer publications, regulator test programmes, insurance claims data and independent consumer testing, and those four sources do not always agree.
Where they conflict, the independent testing and the real-world claims data are usually the more reliable guide, because manufacturer figures are produced under conditions chosen by the manufacturer.
Anything specific to your own vehicle should be checked against its handbook and against a qualified technician familiar with the model, since specifications differ between markets and between production years in ways that general articles cannot capture.