Roadster batteries likely to perform better than Tesla predicted

Once the epitome of EV cool, the Tesla Roadster has kind of taken a back seat to the new electric vehicles in the market it helped spawn. Turns out, even in the background, the Roadster has things to teach us. Or, at least it does to the experts at Plug In America who recently took a closer look at the EV's battery pack.

See, in 2006, when the Roadster was new, Tesla said the Roadster's 53-kWh lithium-ion battery pack – good for 244 miles of range when new – would have 70 percent of its capacity after five years or 50,000 miles. With plenty of "old" Roadsters on the road, PIA studied four percent of the packs out there today and discovered (PDF) that the packs have an "average of 80- to 85-percent of capacity after 100,000 miles driven." The numbers were self-reported to PIA's website by Roadster owners in a project that started in January.

The numbers come from PIA's chief science officer, Tom Saxton, who conducted the first-ever independent assessment and announced the results at the recent Teslive Tesla users conference. According to a statement, he said, "Our study also found no discernable effect of climate on battery-pack longevity. Roadster owners in hot climates are not seeing noticeably different battery capacity profiles than owners in moderate climates." Last year, PIA surveyed Nissan Leaf owners and discovered that hot climates were affecting the packs more than expected. Surveys on the first-generation Toyota RAV4 EV and Tesla Model S are underway.