Plug In America Tests Older Tesla Roadsters, Finds Battery Durability Better Than Promised

TTAC Staff
by TTAC Staff

Tesla Roadster battery pack – Tesla Photo

One drawback to cars that run on batteries is that over time and multiple charge/discharge cycles, batteries will lose capacity. Individual cells start to fail to meet specifications and when enough cells go bad, it’s time for another battery pack. Since capacity is directly related to range and since battery packs are expensive to replace, how quickly batteries deteriorate is an important factor in the overall cost and practicality of EVs.

When Tesla first announced their Roadster EV in 2006, the company said that due the company’s proprietary battery management system and design of their lithium-iom battery packs, would ensure that after five years or 50,000 miles, the Roadster’s battery pack would still have 70 percent of it’s rated capacity when new, 53 kWh, enough electrons for a 244 mile range ( 2006 statement on battery age by Tesla founder Martin Eberhard here). The Tesla Roadster went on sale in 2008, which means there are now roadsters that have been on the road for as long as five years, and I’m sure many that have reached or exceeded 50,000 miles of use. It’s now possible to test Tesla’s claims regarding battery durability. A standard from the laptop industry is that lithium-ion battery packs are still serviceable above 80% capacity.

The independent EV advocacy group, Plug In America (PIA) decided to do just that and their chief science officer, Tom Saxton has reported the results of an owner-reported survey of Tesla battery packs, based on a sample size of 4% of all 2,500 Roadsters made. Plug In America discovered that the Tesla battery packs are performing much better than advertised. After 100,000 miles, double the advertised 70% capacity life, the battery packs have an average capacity of 80-85%.

PIA also tested for climate differences because PIA’s earlier first ever survey of EV battery life involving owners of Nissan Leafs showed measurable declines in battery capacity in hot climates. The Leaf has a much simpler battery heat management system than used by Tesla. A surveys of first generation Toyota RAV4 EV owners, which was on sale from 1997 to 2003, in order to measure performance in batteries at least 10 years old, is also underway, as is a survey of Tesla Model S owners but it’s too early for any real meaningful data to be obtained on that car.

TTAC Staff
TTAC Staff

More by TTAC Staff

Comments
Join the conversation
2 of 67 comments
  • JD321 JD321 on Jul 17, 2013

    Honda has a great lease deal on their Fit EV so if you are self-limiting to a 35 miles radius, then this is the EV you you! You don't have to own an expensive battery pack and they install a home charger for free.

  • BobSmith BobSmith on Jul 29, 2014

    The ICE has been built and refined in large numbers for over 100 years. The BEV only has about 10 years of reasonably small production. Tesla model S with 250+ miles of range certainly makes a great day car. Most people could live with it. There are already battery advances on the horizon that will increase capacity, decrease cost and increase durability. With a battery that had a 500 mile range, lower cost and 10,000 cycle life - the ICE will look like expensive old technology.

  • MaintenanceCosts Other sources seem to think that the "electric Highlander" will be built on TNGA and that the other 3-row will be on an all-new EV-specific platform. In that case, why bother building the first one at all?
  • THX1136 Two thoughts as I read through the article. 1) I really like the fins on this compared to the others. For me this is a jet while the others were propeller driven craft in appearance.2) The mention of the wider whitewalls brought to mind a vague memory. After the wider version fell out of favor I seem to remember that one could buy add-on wide whitewalls only that fit on top of the tire so the older look could be maintained. I remember they would look relatively okay until the add-on would start to ripple and bow out indicating their exact nature. Thanks for the write up, Corey. Looking forward to what's next.
  • Analoggrotto It's bad enough we have to read your endless Hyundai Kia Genesis shilling, we don't want to hear actually it too. We spend good money on speakers, headphones and amplifiers!
  • Redapple2 Worthy of a book
  • Pig_Iron This message is for Matthew Guy. I just want to say thank you for the photo article titled Tailgate Party: Ford Talks Truck Innovations. It was really interesting. I did not see on the home page and almost would have missed it. I think it should be posted like Corey's Cadillac series. 🙂
Next