Geotab has released updated findings from its third large-scale study on electric vehicle battery degradation, analyzing data from over 22,700 EVs across 21 makes and models using several years of aggregated telematics information.
The conclusion is reassuring for fleets and consumers alike: modern EV batteries are holding up well, with degradation rates remaining low enough to support extended vehicle lifecycles. However, how vehicles are charged—especially reliance on high-power DC fast charging—now plays the most significant role in battery aging.
Understanding Battery State of Health
The study evaluates State of Health (SOH), a measure of a battery’s remaining capacity compared to when it was new. According to Geotab’s analysis:
- Average battery degradation is 2.3% per year
- This aligns with the company’s original 2019–2020 findings
- The projected average SOH after eight years of use is 81.6%
While slightly higher than the 1.8% annual degradation reported in Geotab’s 2024 study, the figure still supports long-term EV ownership and fleet deployment.
“Because we track EV data globally, we’re able to aggregate insights that help answer critical questions around battery longevity and return on investment,” said Charlotte Argue, Senior Manager at Geotab, in an interview with Freight Waves.
Why Degradation Rates Rose Again
Several factors explain the return to the 2.3% annual average:
- The latest study covers 21 vehicle models, nearly double the number in earlier reports
- A higher share of newer vehicle, which typically experience faster degradation early in life before stabilizing
- Increased dependence on high-power DC fast charging
Among these, charging behavior stands out as the most influential variable.
Charging Power Emerges as the Dominant Factor
Geotab’s data shows that charging power and frequency now outweigh most other operational factors when it comes to battery health.
Key findings include:
- Vehicles frequently using DC fast charging above 100 kW showed average degradation of 3.0% per year
- Vehicles relying primarily on AC or lower-power charging averaged 1.5% per year
- Even with heavy fast-charging use, degradation remains modest
“Our data shows charging power and frequency are the strongest influences on degradation,” Argue said. “Even for vehicles using high-power charging often, average degradation is still only around 3% annually.”
Debunking the 20–80% Charging Myth
The study challenges the widely circulated advice that EV batteries must always be kept between 20% and 80% charge.
Geotab’s analysis found:
- Regularly charging to 100% does not significantly harm long-term battery health
- Degradation only increases if vehicles remain at very high or very low charge states for more than 80% of their total time
- The difference in degradation between users capping at 80% and those occasionally charging to 100% was negligible
“Fully charging or depleting batteries doesn’t negatively impact long-term health for most users,” Argue explained. “It only becomes an issue when vehicles sit at those extremes for prolonged periods.”
Climate and Usage Effects
While less influential than charging behavior, environmental and operational factors still play a role:
- Vehicles in hot climates degraded about 0.4% faster per year than those in mild conditions
- High-utilization vehicles experienced roughly 0.8% higher annual degradation compared to low-use vehicles
Despite this, Geotab notes that higher productivity and asset utilization typically outweigh the incremental degradation, particularly for commercial fleets.
What This Means for Fleet Operators
For fleets considering or expanding electrification, the findings point to a balanced charging strategy.
Geotab recommends:
- Matching charging infrastructure to operational needs
- Using lower-power charging when vehicles have extended dwell time, such as overnight depot parking
- Reserving high-power DC fast charging for routes and operations that require rapid turnaround
“The focus should be balance,” Argue said. “Use fast charging when it’s essential and rely on lower-power charging whenever vehicles have sufficient downtime.”
Longer Lifecycles, Lower Total Cost of Ownership
The durability of modern EV batteries opens the door for fleets to keep electric vehicles in service longer than traditional internal combustion vehicles.
With fewer moving parts, lower maintenance needs, and batteries lasting longer than initially expected, fleets can improve total cost of ownership and return on investment by extending vehicle lifecycles.
“There’s a real opportunity for fleets to keep EVs longer than gas vehicles,” Argue said, “driving down costs while increasing ROI.”
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