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.
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Plug In America Research Shows That Tesla Roadster Battery Performance Bests Tesla Motors' Own Projections

First-Ever Independent Assessment Demonstrates Strong Battery Life

MILPITAS, Calif., July 13, 2013-Battery packs in Tesla Motors' Roadster electric cars will retain an average of 80- to 85-percent of capacity after 100,000 miles driven, according to a study published today by Plug In America, the nation's leading plug-in vehicle advocacy organization. The finding, released here at the Teslive Tesla users conference, bests initial projections set by Tesla Motors in 2006 which suggested a 70-percent capacity retention after five years and 50,000 miles driven, said Tom Saxton, Plug In America's chief science officer.

"Our study also found no discernable effect of climate on battery-pack longevity," said Saxton, who lead the research. "Roadster owners in hot climates are not seeing noticeably different battery capacity profiles than owners in moderate climates."

Plug In America launched the first-ever survey in January 2013, receiving data from about 4 percent of Roadster owners worldwide who completed a form on the independent, nonprofit organization's website. This was combined with anonymous data from OpenVehicles.com, an aftermarket vehicle monitoring system.

Studying the Nissan LEAF EV, Plug In America conducted the first-ever evaluation of plug-in battery performance last year. The purpose of these studies is to help consumers better understand battery reliability, support industry-wide adoption of standard battery performance warranties, and inform consumers making extended-warranty purchase decisions. Andy Palmer, executive vice president of Nissan Motor Co., Ltd., encouraged every LEAF owner to read the survey's results when Nissan announced the addition of capacity-loss coverage to an enhanced LEAF battery warranty.

"Plug In America's goal has always been to educate as well as to advocate," Saxton said. "We continue to accelerate the shift to cleaner, more affordable, more fun electrified personal transportation by disseminating information that's useful to consumers and vehicle manufacturers."

Plug In America has also launched battery-pack performance surveys of the 1997-2003 Toyota RAV4-EV and the new Tesla Model S. The RAV4-EV survey will document the 10-year experience of owners of these early electric vehicles.

It is premature to glean much about battery capacity for the Model S, which became available in mid-2012, but this research has already shown that survey participants are driving an average of more than 16,000 miles per year, well above the national average of 13,500 miles for conventional vehicles, Saxton reported.

In addition to heading up Plug In America's battery performance research, last year Plug In America conducted the first-ever performance evaluation of public EV charging infrastructure effectiveness including charging station reliability, availability and average-use levels.

About Plug In America: Plug In America is the preeminent advocacy organization advancing the plug-in vehicle market. The nonprofit organization works to accelerate the shift to plug-in vehicles powered by clean, affordable, domestic electricity to reduce our nation's dependence on petroleum and improve the global environment. For more information: http://www.pluginamerica.org.

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