“We see variation between different vehicles and models,” Argue continues. There are other factors too. “So far we have not seen a significant impact of high mileage on the degradation rate, so you should not be afraid to use your EV.” This finding is consistent with P3's research.
“But we have seen a correlation with the frequency of DC fast charging,” Argue warns. “Cars that frequently fast-charged had a noticeable increase in degradation.”
Warm weather is also a factor that affects durability. “In the worst case, it was three times higher for a particular model that drove in warm climates and fast-charged regularly,” Argue says. This would mean that 5.4 percent of the battery capacity is lost per year. But “the best had an average of 1 percent degradation per year. It is definitely a positive trend that we are seeing.”
“When the electric vehicle market started, there was a lot of concern about the factors that could lead to greater battery degradation,” said Neil Cawse, CEO of Geotab. “For example, completely discharging, charging in cold weather versus warm weather, fast charging versus slow charging. But battery technology has gotten much better, especially in the area of management systems, for example by ensuring that lithium-ion cells charge properly when they are cold.”
This better battery performance can provide longer guarantees for higher remaining capacity. Toyota has been offering a ten-year warranty on its EV batteries, and MG is experimenting with a lifetime warranty in Thailand. “Generally speaking, you still have guarantees that promise 70 percent health after eight years, but the degradation we see with those batteries is much less,” Wallace says.
Your EV can still be good after 20 years
However, research to date is based on how the car's systems report the health of the battery. “I would take all those values with a grain of salt,” says Wallace. “The reported health status on the dashboard that the customer sees often differs significantly from what the customer sees factual The health condition comes from that battery.” According to a report published by Elysia in 2023, actual health conditions may differ by up to 9 percent from what is reported.
Another problem is the buffer that manufacturers leave in their batteries: the difference between net and gross capacity in kWh. “OEMs oversize these batteries,” says Wallace. However, Argue explains that “there has to be a safety buffer because what we know from battery science is that if a battery is left completely full or completely empty for an extended period of time, it causes more stress. Having a buffer protects the battery from degradation.”
Wallace believes this buffer is too conservative given the low degradation seen in EV batteries. “They don't need that much excess capacity,” he says. “Smaller buffers mean smaller batteries, which reduces the cost of electric vehicles.” The problem is that Wallace believes many traditional automakers don't yet have the necessary data on their own batteries to take this step.
But if the batteries last a long time, as the P3 and Geotab studies imply, electric vehicles could be in better condition than internal combustion vehicles of the same mileage and age. The rest of an EV is also cheaper to use. “The maintenance costs are significantly lower,” says Cawse. “You maintain the brake pads and replace the windshield wipers – and that's it.”
A ten year old electric car can be almost as good as new, and a twenty year old electric car can still be used. That could mean yet another disruption for an auto industry that depends on cars that largely end up being scrapped after 15 years.
