Electric vehicle batteries degrade at an average rate of 2.3% per year, according to a comprehensive analysis of over 22,700 vehicles covering 21 different models.
The study by global telematics company Geotab confirms that modern EV batteries are robust and built to last beyond a typical vehicle’s service life, with batteries projected to retain 81.6% of their original capacity after eight years.
However, the research reveals significant variations in degradation rates depending on charging habits, climate conditions and usage patterns – factors particularly relevant for Australian EV owners given the country’s hot climate and expanding fast-charging network.
“Battery degradation, or the gradual decline in a battery’s ability to store energy, affects your driving range, performance and the vehicle’s resale value,” says Charlotte Argue, senior manager of sustainable mobility at Geotab.
High-power charging doubles degradation rate
The study identifies high-power DC fast charging above 100kW as the single largest stressor on EV batteries, leading to degradation rates up to twice that of vehicles using predominantly lower-power charging.
Vehicles that frequently used high-power DC fast charging experienced annual degradation of 3.0%, compared to just 1.5% for those relying primarily on lower-power charging methods.
The analysis grouped vehicles based on their DC fast charging usage, revealing a clear correlation between charging power and battery wear. Vehicles using DC fast charging for less than 12% of total charging sessions averaged 1.5% annual degradation, while those exceeding 12% usage saw degradation increase to 2.5%.
When high-frequency DC fast charging users were further divided by power levels, the impact became more pronounced. Vehicles where more than 40% of DC fast charging sessions exceeded 100kW experienced the highest degradation rate of 3.0% annually.
Hot climates add degradation penalty
Climate conditions significantly impact battery longevity, with vehicles operating in hot conditions degrading 0.4% faster per year than those in mild climates.
The study grouped vehicles based on days exceeding 25°C, finding that those experiencing more than 35% of days above this temperature showed measurably faster degradation rates.
This finding has particular relevance for Australian EV owners, given much of the continent experiences extended periods of high temperatures. The research suggests an EV operating in hot conditions like those found across much of Australia will likely have a shorter battery life than the same model in cooler climates.
State of charge management less critical
Contrary to common advice suggesting EV owners should keep battery charge between 20% and 80%, the study found this practice is only critical if batteries are habitually maintained at extreme charge levels for extended periods.
The analysis revealed that moderate exposure to extreme state of charge levels does not significantly accelerate degradation. Only vehicles spending more than 80% of their total time at very high or very low charge levels experienced notably faster battery wear.
“The battery is designed to handle normal use across its entire charge range,” the study notes, explaining that modern EV batteries incorporate hidden software buffers that protect against damage from full or empty states.
High utilisation manageable trade-off
Vehicle utilisation also affects battery life, with high-use vehicles showing increased degradation rates. However, the study suggests this represents a manageable trade-off for fleet operators seeking to maximise productivity.
Vehicles completing the equivalent of a full charge cycle every 1-2 days experienced 2.3% annual degradation, compared to 1.5% for those cycling every seven or more days – a difference of 0.8%.
After eight years, high-use vehicles are projected to retain 81.6% of battery capacity, while low-use vehicles maintain 88% – both levels considered highly functional for continued operation.
Strategic charging recommendations
The research emphasises the importance of strategic charging power selection, particularly as the industry trends toward higher-power charging capabilities.
Geotab’s data shows reliance on high-speed DC fast charging has nearly tripled across their customer base, jumping from less than 10% to about 25% of all charging sessions, with average power increasing from roughly 70kW to over 90kW.
The study recommends using the lowest power level that meets operational requirements, reserving high-power DC fast charging for essential needs rather than making it the default charging method.
For Australian fleet managers and EV owners, the findings suggest careful consideration of charging infrastructure investments and operational strategies to maximise battery life while meeting practical requirements.
The complete Geotab EV battery health analysis can be found at www.geotab.com/blog/ev-battery-health.
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