Published on July 20th, 2013 | by Nicholas Brown


Tesla Roadster Battery Banks Forecast To Retain 80–85% Charge Over 100,000 Miles

July 20th, 2013 by  

This article was first published on EV Obsession.

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.

Tesla Roadster - Deskinned Image Credit: Jurvetson on Flickr

Tesla Roadster – Deskinned
Image Credit: Jurvetson on Flickr

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!

california tesla roadster EV

California-made Tesla Roadster
Image Credit: GS1311

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.

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About the Author

writes on CleanTechnica, Gas2, Kleef&Co, and Green Building Elements. He has a keen interest in physics-intensive topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography. His website is:

  • Others


    Similarly among the 1st generation Prius and Insight, 85 % of the vehicles sold are still running on the World’s road. Prius was first launched in December 1997 and some of them which were used in Taxis would have worn out.

    In fact many Prius Taxi’s clocked 350,000 miles (560,000 km).

  • Ivor O’Connor

    A few things caught my interest.

    Mileage is way off. Though I hate driving and avoid it until I can do multiple things on a single trip I have put on 200K in 10 years. Double Tesla’s estimate. I expect Tesla’s to support my driving mileage regardless of their warranty.

    The battery pack is made up of thousands of AAA like cells. Putting together a pack of this magnitude must be a first of its kind. I’m pretty sure these packs are instrumented down to the cell so outliners can be identified and replaced. So the packs can be quickly “repaired” and continue making customers for decades. However why don’t we hear anything about this?

    Finally the article says basically your mileage may vary. Greatly. So somebody is keeping stats. Where are they being kept?

    • dynamo.joe

      Almost no one will offer a warranty that disregards usage rates. Most car warranties are of the 10yr/100k mile variety.

      At 20k/yr you are a six sigma outlier. It’s a better business decision to write you off as a customer than try to engineer a system or offer a warranty that would cover that kind of mileage.

      • Ivor O’Connor

        Yes, nobody does a warranty like that. Yet. These Tesla vehicles though are something else. With all aluminum for the most part they are not going to fall apart like the current crop of mechanical monstrosities. I would not be surprised to see them last for 50 years with little maintenance. If we can replace out the outlier cells.

        By the way how did you come out with 20k/yr being a six sigma? I don’t have driving mileage charts but I don’t drive that much compared to others. I would not even think I’m a two sigma driver. A six sigma driver I would expect to put on more mileage than the average long haul trucker. Or more than 5K a week for 50 weeks a year or 250K a year. Have you got stats to back the sigmas?

        • dynamo.joe

          I guess I only remembered the overall average which is 13k, but if you’re a male 35-54, you’d only be at 1 sigma or so.

          • Ivor O’Connor

            Interesting age based averages…

      • Bob_Wallace

        Tesla is giving 8 year, unlimited mileage coverage on the 300 mile range versions of the S.

        For someone who spends a lot of their time driving, that should be attractive.

        • Ivor O’Connor

          Yes indeed.

          85 kWh BATTERY
          265 miles range (EPA)
          0-60 mph in 4.2 seconds
          8 year, unlimited mile battery warranty
          Supercharging included
          … and …

          Delivers in about 2 months!!!!

    • Bob_Wallace

      There is something on the web about the ability to remove and replace “blades” or “sleeves” of cells. Not finding it right now.

      The ability to swap out a S battery would mean that you could drop off your pack for repair and drive away with a loaner pack.

      With Roadster battery packs still in the 80% to 85% range at 100,000 miles I suspect batteries are more robust than most believe. GM has made an offhand statement about their Volt batteries lasting better than predicted.

      Of course if Eos can fit in their zinc-air batteries with their >10,000 cycle lifespan then we can forget battery life. In a 200 mile range EV those would be 2 million mile batteries.

      • Ivor O’Connor

        I haven’t heard of these zinc-air batteries yet. They would be fantastic.

        If you do find info on these “blades” or “sleeves” please let me know.

        I’m sure one way or another these Tesla vehicles will probably last almost forever.

        • Bob_Wallace

          Follow the link to the Eos web site for EV info.

          We should know fairly soon if Eos is for real or blowing smoke.

          • Ivor O’Connor

            I’ve let my own expectations cloud my learning I suppose. In particular because I don’t expect revolutionary disruptive change in battery technology I don’t read these articles. I should do the extra mile and actually read them even if I can’t bring myself to actually believe in them…

          • Bob_Wallace

            I expect some sort of a breakthrough in the not too distant future. There are so many different approaches that are working to some extent. If you assign only a 10% chance of success to each the aggregate odds that one works is fairly high.

            EOS is saying that they’ve figured out the grid thing. Cost and cycles make their battery a winner if they can develop an EV version.

            Envia is being track tested by GM. Apparently. GM is testing something and they own a piece of Envia.

            Chrysler has been testing Electrovaya. They weren’t happy with it but they were asking it to do more than just power PHEVs.

            I’ve got to think that the big battery companies are working on their approaches behind closed doors. And there have been a number of promising findings coming out of university labs.

            I try to learn as much as I can about them. But I’m not going to declare the job finished until someone produces a breakthrough battery and it’s proven in the real world.

          • I’m personally not a fan of reading articles regarding breakthroughs / potential breakthroughs unless they are hitting the market or about to hit the market. (You may have noticed that I don’t actually author many of those pieces.) Eos starting pilot projects with a ton of huge partners… initially for grid storage. It should be getting close if it really is going to bring something competitive to market. We’ll see. I’m keeping my eye on this company, Envia (since it is working closely with GM), and some of the existing major corporations in this space (LG Chem, Johnson Controls, Panasonic, Toshiba, Samsung We’ll see…

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