A study of 21 electric vehicle models — and the introduction of an accompanying interactive tool — brings promising insights for real-world battery longevity
“While there has been plenty of research done on battery health, there has been very little data following the real-world performance of EVs over time, let alone comparisons across different makes and models,” writes Charlotte Argue, senior manager of fleet electrification at Geotab. “Until now.”
The key takeaways are quite positive: batteries are exhibiting “high levels of sustained health” over long periods of use.
“If the observed degradation rates are maintained, the vast majority of batteries will outlast the usable life of the vehicle,” writes Argue.
Modest range loss
Across the 21 vehicle models observed, the average loss to a battery’s state of health was modest — only 2.3% per year. For an EV with a 240-kilometre range, that amounts to only about 27 kilometres of lost range after five years of use.
In conjunction with the report, Geotab also unveiled an interactive tool that users can use to compare rates of battery degradation between cars of different makes, models and years.
The 2015 Nissan Leaf, for example, has an average degradation rate of 4.2%, while that of the 2015 Tesla Model S is only 2.3%. Geotab cites battery pack temperature control as the key difference between these models; the Tesla’s liquid cooling system protects the battery against degradation more effectively than the Nissan’s passive air-cooling system.
Buffers aid longevity
Another key factor in battery longevity is the use of a state-of-charge buffer. Continuous operation of a battery at either its maximum or minimum end can damage its long-term health. As such, cars which utilize large buffers which prevent a battery from becoming entirely depleted or fully charged ensure lower than average degradation rates.
Higher vehicle usage did not statistically show to increase rates of battery degradation. However, frequent usage of direct-current fast chargers, as opposed to 120V or 240V chargers, appears to accelerate degradation. Vehicles driven in hot climates (more than five days per year over 27°C) were also shown to have higher rates of battery degradation than those which remained in more temperate conditions.