‘Lithium’ battery capacity degradation is one of the main concerns of electric vehicle buyers and potential buyers. Since the resurgence of electric cars is relatively recent, meaningful long-term data on large battery packs is fairly rare. Only Tesla has battery packs with a capacity higher than 30 kWh on the road in any significant number and they only have been in operation for a few years (Roadster aside).
But a few Tesla owners have accumulated impressive mileage on their vehicles and the data provides an interesting look into potential battery capacity degradation.The electric vehicle advocate group, Plug-in America, is always independently gathering data on Tesla vehicles, especially through its Model S Survey.
The organisation added a few entries in the past months and now has data on close to 500 Tesla vehicles with a total of over 12 million miles driven.
Data shows that the Model S’ battery pack generally only loses about 5% of its capacity within the first 50,000 miles and then the degradation significantly slows down with higher mileage. Plug-in America’s data shows several vehicles with over 100,000 miles driven and less than 8% degradation.
Here’s the chart for reported battery capacity versus miles driven for each of the vehicles in the Model S survey:
Battery capacity can be affected by several factors like frequent full capacity charging, periods of time uncharged and fast-charging.
Plug-in America’s data also shows that replacement rates for major components have significantly improved:
The early data is encouraging, but furthermore. Tesla is still working on improving its battery pack and cell technology. The company entered into a research partnership with Jeff Dahn’s battery-research group at Dalhousie University. Dahn specializes in li-ion battery cell longevity, which should be very helpful in achieving high mileage on battery pack with little capacity loss.
CEO Elon Musk once referred to a battery pack Tesla was testing in the lab. He said that the company had simulated over 500,000 miles on it and that it was still operating at over 80% of its original capacity.
Featured image: Reuters/Lucy Nicholson and other images via Plug-in America