Do EV batteries really degrade that fast?

EV batteries gradually lose usable capacity as they age. Recent research by Geotab found an average degradation of 2.3% per year. That figure is an average, not a countdown clock. Battery chemistry, temperature, charging power, usage and the car’s battery-management system all affect the result. Degradation may also be faster during some periods and slower during others.

Even at an average rate of 2.3%, a battery would retain around 80% of its original capacity after nine years. The car would have less range than when it was new, but that makes the battery far from useless.

A new battery has a certain amount of usable capacity, measured in kilowatt-hours. As the battery ages, chemical changes inside its cells reduce the amount of energy it can hold. This affects range. Imagine an EV that could travel 400 kilometres when it was new. If the battery retains 90% of its original usable capacity, your range under similar conditions might be closer to 360 kilometres.

In practice, the difference can be difficult to spot from day to day. Weather, speed, tyre pressure, terrain and heating or air conditioning can all change range too. A disappointing winter journey is therefore not proof that the battery has suddenly aged. For more on that distinction, read our guide to what weather does to an EV’s range.

Battery degradation should not be confused with battery failure. Degradation is a gradual loss of capacity. Failure means that the battery or one of its components develops a fault. A degraded battery can still work reliably; it simply stores less energy than it once did.

The classic, not entirely satisfying answer is: it depends. There is no single degradation rate that applies to every EV. Geotab’s latest analysis found average annual degradation of 2.3% across almost 23.000 vehicles from 21 different makes and models. Geotab’s earlier research found a lower average. That does not mean EV batteries have suddenly started ageing faster: the studies included different vehicles, used under different conditions. Age, climate and charging behaviour all affect the outcome, so the average is a useful indication rather than a universal rule.

Degradation is not always perfectly linear either. A battery may lose capacity relatively quickly early in its life, settle into a slower period and change again as it becomes older. Multiplying one year’s loss by the age of the car can therefore produce a misleading prediction. The US Department of Energy’s Alternative Fuels Data Center says current EV batteries may last between 12 and 15 years in moderate climates, or between 8 and 12 years in extreme climates. Many manufacturers support them with separate battery warranties, often covering around eight years or 160.000 kilometres.

Those warranties do not usually promise that the battery will remain exactly as it was on day one. Instead, they commonly guarantee that its capacity will not fall below a specified threshold during the warranty period. The exact terms and conditions vary, so it is worth reading the small print before buying the car rather than after the dashboard range begins to look suspicious.

Time plays a role, but the way the battery is used and stored matters too.

• High temperatures
  Heat speeds up the chemical reactions that cause batteries to age. Modern EVs use cooling systems to keep the battery within a safe operating range, but prolonged exposure to high temperatures can still affect its long-term health. Geotab found that vehicles in hot climates degraded around 0.4 percentage points faster per year than those in milder climates.
  

• Frequent high-powered charging
  Rapid charging is extremely useful on long journeys. It also places more stress on the battery than lower-powered charging, particularly when used very frequently. In Geotab’s research, vehicles that relied heavily on fast charging above 100 kW showed degradation of up to 3% per year, compared with around 1,5% among vehicles primarily using AC – the slower type commonly used at home or at regular public charging points – or lower-powered charging.
  
  
• The useful word here is heavily. Occasionally using a rapid charger on a long trip is different from relying on one for almost every charge. There is no need to avoid fast charging altogether, but slower charging at home or work is generally kinder to the battery when it is practical.
  
  
• Spending long periods completely full or nearly empty
  Batteries are generally most comfortable somewhere in the middle of their capacity. Leaving an EV at 100% for a long time, particularly in hot weather, can increase stress on the cells. Repeatedly running it extremely low can have a similar effect. Many cars allow the driver to set a daily charging limit, often around 80%. Charging to 100% before a long journey is perfectly reasonable; the main point is to avoid leaving the car completely full for days when the extra range is not needed.

The car’s own manual remains the best guide. Battery chemistries differ, and some manufacturers recommend regularly charging particular battery types to 100% so the management system can calculate their capacity accurately.

Usually, a gradual reduction in capacity does not require any repair at all. The owner simply has slightly less range available. If a fault does develop, it doesn’t automatically mean you need to replace the complete battery pack. Depending on the design of the car, individual modules, electronic components or cooling-system parts may be repairable or replaceable.

A full battery replacement can be expensive. That fact understandably worries used-EV buyers, but it should be considered alongside the likelihood of failure, the remaining warranty and the actual condition of the battery. Theoretical replacement cost tells you little about whether a particular car is likely to need one.

A battery that no longer offers enough range for demanding driving may also remain useful for a less demanding owner or eventually find a second life in stationary energy storage. After that, materials including lithium, nickel and cobalt can be recovered through recycling. The system is not yet perfectly circular, but an ageing battery does not automatically become several hundred kilograms of useless waste.

This is where battery degradation becomes more than a technical discussion. For someone buying a used EV, the important question is not how batteries age in general, but how well the battery in this particular car has aged. State of Health, usually shortened to SoH, compares the battery’s current usable capacity with its original capacity. A battery with an SoH of 90% retains roughly 90% of the energy it could store when new.

That percentage is generally more informative than mileage alone. Two EVs with the same number on the odometer may have different battery health because they were charged, driven and stored differently. We cover the checks in more detail in our guide to buying a used. In short, ask for a recent battery-health report, check what remains of the battery warranty and make sure the car’s current range and charging speed suit your journeys. Better access to this information can remove much of the uncertainty from buying used. On OLX Group marketplaces, battery information is becoming more prominent. Standvirtual, Autovit and OTOMOTO can display details such as battery capacity, charging specifications and State of Health where available.

A percentage in a listing is a useful starting point rather than the whole diagnosis. Buyers should still ask how it was measured and request the certificate or report behind it. European rules should make that transparency increasingly normal. The EU Batteries Regulation introduces requirements concerning battery durability, State of Health information and digital battery passports for EV batteries. The aim is to make battery performance easier to trace throughout its life.

Battery degradation deserves attention, particularly when buying an older electric car, but it does not mean every EV is approaching an enormous repair bill. For new-car buyers, the battery warranty and expected future range matter; for used-car buyers, a reliable State of Health report turns an intimidating unknown into another specification to compare. EV batteries do degrade, the surprising part is how slowly most of them do it.