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Frequently Supercharging Your Model X Bad For The Battery?

Discussion in 'Model X' started by dragonxt, Jun 15, 2017.

  1. dragonxt

    dragonxt Active Member

    Oct 26, 2016
    Bay Area
    Is fast charging your Model X at a Supercharger significantly worse for your battery?

    It seems like my driving routes require me to Supercharge a few times per week, would this harm my battery?
  2. Matteo

    Matteo Member

    Jul 6, 2015
    #2 Matteo, Jun 15, 2017
    Last edited: Jun 15, 2017
    Hi. There is no data to support the argument that supercharging more often is bad for the battery. The two charts below are from the MaxRange Tesla battery survey. The second chart with the blue dots shows remaining range versus mileage. Each dot represents an entry. Many users submit multiple entries. All of these are shown here. The red trendline shows the average user. Some entries are above the trendline, some are below.

    The first chart shows what percentage of users are above the trendline. For example, 71 people said they supercharge twice a month. 41 of those are above the trendline. That's 57.75%. Therefore you see a bar that's 57.75% green. The longer the green bar, the higher the percentage of people who are doing better than the average user.

    To make this as accurate as possible, the first chart considers only the last entry by each user. Otherwise, somebody who submits 20 entries would mess up the accuracy. Therefore only the last entry of each user counts. This was technically difficult to implement but I thought it was worth it.

    Unfortunately, some options were selected by too few people, therefore the precision is negatively affected. For example, only 6 people said they supercharge once or twice a year. With so few people, a single person represents %16.67. That's not very precise. Therefore entries with fewer people should be considered less precise.

    If you look at answers that were selected the most, those are option D, E and F. They show a slight advantage for supercharging more often. In other words, supercharging monthly seems to be slightly better than supercharging a few times a year and supercharging twice a month seems slightly better than supercharging monthly. However, then we have the supercharging weekly option which is 50%-50% but on the other hand, doesn't have as many entries.

    Therefore it is a little difficult to say at this stage that supercharging more often is better for the battery, even though the trend points towards that direction. However, what I can say is that the data doesn't show that supercharging often is bad. In conclusion, I wouldn't worry about supercharging frequently.

    As a side note, the 90 kWh battery might have some limitations (it could be related to cooling) and therefore supercharging the 90 kWh often might not be a great idea. There is anecdotal evidence that Tesla has implemented a supercharge counter into 90 kWh Model S/X cars where the peak power of supercharging is permanently reduced for the rest of the life of the car once it reaches 300 DC charging sessions (total 300 supercharge or chademo charge sessions). If somebody has a 90 kWh pack, they might want to check out this topic: If you fast charge, Tesla will permanently throttle charging

    Source: MaxRange Battery Survey, Stats page, rows 14:24

    Source: MaxRange Battery Survey, Charts page
    • Informative x 3
    • Like x 1
  3. chillaban

    chillaban Active Member

    May 5, 2016
    Bay Area
    Note that there is some talk about, at least on certain battery packs, frequently supercharging may cause your max charge rate to be limited. But I think a lot of that drama is blown out of proportion in terms of the slight charge speed limit and the sheer number of cycles required to hit that.
  4. MasterT

    MasterT Member

    Dec 19, 2016
    North Miami Beach, FL
    The answer to the question as stated - NO.

    Could there be some negative effect on the battery from frequent DC charging (including supercharging) - possibly, but no evidence yet.

    Could Tesla change your supercharging curve if frequently charged from DC - appears so.
  5. gearchruncher

    gearchruncher Member

    Sep 20, 2016
    Seattle, WA
    I know supercharging feels fast, but it's not.
    Batteries are rated at "C" charge rates. 1C means fully charging in 1 hour. 1 hour for 1 capacity. So 2C would be charging in 30 minutes, and 0.5C would be in 2 hours.
    The great thing about "C" is that it's a ratio of the whole battery size. Doesn't matter if it's a cell phone battery or a car battery, 1C means one hour, even though the car takes 10,000 times the power.

    Now, pretty much every Lithium chemistry can easily take 1C. It's considered the simple and safe level. Most phones and laptops can charge this fast. In the model airplane world, people run batteries that can charge at 5C or 10C. Imagine charging your car in 6 minutes!

    The supercharger doesn't even really run at 1C. It can peak at about 1.2C, but for only short periods of time. So this is still a very gentle charge for a battery. I know it feels weird because it can be 120kW, but each individual battery is seeing more like 15W, which sounds perfectly reasonable.
    • Informative x 4
  6. EinSV

    EinSV Active Member

    Feb 6, 2016

    Thank you for posting the data and for your analysis -- very helpful to have the big picture.

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