Plug In America (PIA) has released a study by its Chief Science Officer (and Charged contributor), Tom Saxton, designed to predict the longevity of Tesla Roadster battery packs, based on user data. The advocacy organization used data voluntarily submitted by Roadster owners, as well as data collected anonymously through the Open Vehicle Monitoring System. 126 vehicles contributed to the survey, representing about 5% of owners and 10% of miles driven.

The study’s key findings:

• Of the factors considered – miles driven, vehicle age, and climate – only mileage showed a significant correlation with battery pack capacity.
• Data collected suggests that, on average, a Roadster battery pack will have between 80% and 85% of original capacity after 100,000 miles.
• Unlike results from the Plug In America LEAF Battery Survey, no significant correlation was found between climate and battery longevity.
• 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 this wide variation in longevity, the study notes that automakers should guarantee not only the life of a battery pack, but also the capacity performance over time and miles. Nissan currently offers a capacity warranty, but Tesla does not.

Source: Plug In America