This isn’t terribly surprising to me, as electric vehicle battery packs are often provided with 8-year warranties, and there is a rule of thumb that the lifespan of equipment normally exceeds its warranty. (Otherwise, the manufacturer would end up replacing everyone’s equipment.) Still, it’s good to hear that someone has tested Tesla Roadster Battery Banks and they are projected to retain 80–85% of the initial full charge after 100,000 miles, much better than Tesla initially claimed.
An 8-year warranty does mean that you will get at least 8 years, unless there is a defect. That’s quite a long time, especially for a something being used in a new type of high-performance car. The Tesla Roadster, which is an electric sports car introduced years ago that can accelerate from 0 to 60 mph in 3.9 seconds has a 53 kWh lithium-ion battery bank, and I used to worry about the cost of replacing it, due to its tremendous size. Big batteries cost big money. I certainly hoped it would last long.
Plug In America predicted that it would last more than 100,000 miles (which translates into 7 to 10 years of average driving), which is reportedly average for electric vehicle battery packs today.
This forecast was revealed at the Teslive Tesla users conference (a partnership between Tesla Motors Club (TMC) and Tesla Motors), and it far exceeded Tesla Motors’ own predictions from 2006 — a 5-year, 50,000-mile lifespan!
According to the study:
There is significant variation in battery capacity reported; the difference in capacity between vehicles with similar mileage can be as large as the projected loss over 100,000 miles of use. Individual owners should therefore expect variation between their experience and the projected average performance.
Because of the variation in battery pack longevity experienced by owners, especially where such variation may be due to factors beyond the owners’ control, it would seem desirable for the manufacturers of electric vehicles to guarantee not only the life of the battery pack, but also the capacity performance over time and miles.