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Any harm to battery on the low end?

Discussion in 'Model S: Battery & Charging' started by tnt1971, Mar 22, 2016.

  1. tnt1971

    tnt1971 Member

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    I have read most of the posts on charging and I completely understand that high levels of charge and/or high levels of heat degrade the battery quicker. I have a charger at work, which is only 14 miles each way, and I typically charge to 150 miles each day and get back with more than 100 miles the next morning. I do not yet have a NEMA 14-50 at home, but am awaiting a quote on an install. I do currently have a 110 outlet in the garage to give me enough miles to get back to the office, if need be. My garage temperature almost never goes below 50 and never goes above 90.

    My question has to do with weekends. I would typically charge up to 90% on Friday afternoon and deplete the charge over the weekend till I get back to work on Monday morning. Is there any harm to doing this, particularly if I get back to work on Monday in the 10% range?

    I have an 85D with just under 1,000 miles that I have had for two weeks.
     
  2. TexasEV

    TexasEV Active Member

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  3. byan1232

    byan1232 Member

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    I am under the impression that the battery should be constantly charged to 90% for the least degradation.
     
  4. Electric700

    Electric700 Member

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    Actually 50% would be the ideal value for battery longevity, which is why you can set the car to charge to that level. It's also the level you should keep your car at if it won't be used for several days or longer.

    Tnt1971, if you can charge every weekend once so that you are able to get to work Monday with more than 20% of your range remaining, I think that will be better for your car over the long term.
     
    • Helpful x 1
  5. kort677

    kort677 Active Member

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    while it is never good to let the battery sit for extended periods of time at either extreme, short periods of time at low charge levels or 100% should have little effect on the battery.
    FWIW: I keep my car charged at close to 90% the majority of the time and I am now on my second tesla and over 2 years of ownership I've seen no harm in doing so,
     
  6. David99

    David99 Active Member

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    There is no harm with running the battery down to 10%. Not at all. That's perfectly fine for the battery. The car has many systems in place to keep the battery from getting damaged. The car will not allow you to deplete the battery to a harmful level. The car will shut off before the battery drops too low. It will reduce your power to make sure the voltage never drops below a harmful level.
    Keeping the battery at 10% is also not harmful. Lithium battery age quicker when charged fully or near full. Low levels of charge are fine.

    But there are still reasons not to do it. If anything comes up, a 10% buffer isn't much. If it gets cold, you lose capacity as well. The car will start to reduce AC and heating to save energy. So just from a convenience factor and being on the save side I'd try to keep the buffer higher. But from a battery health point of view, 10% is perfectly fine.
     
  7. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    The lower the charge the more the cells heat up when delivering power. That is when delivering X amount of power the internal heat generated will be greater at 10% than at 90%.
     
  8. sorka

    sorka Active Member

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    Also, keep in mind that repeated large swings in charge level aren't that great. The anode expands as it absorbs Lithium Ions. The higher the charge, the larger the volume the anode takes. The lower the charge, the less volume it takes. Large changes in charge result in larger changes in volume which results in more fracturing of the anode. Ideally, you'd get the best life if you could keep it near 50 % all the time but you can't because the car would be useless.

    Bottom line is I just wouldn't worry about it but I would try mitigate going from 90% to 10% repeatedly. When the car isn't in use, keep it plugged in and charged to 60 or 70%. Then charge more right before you go on a trip *if* you're going to need the range.
     
  9. liuping

    liuping Active Member

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    I would plug it in to the 110 outlet on the weekends. At 3-4 miles per hour, it should be able to keep you over 10%.
     
  10. David99

    David99 Active Member

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    That actually seems to be not true. According to a conversation with Jeff Dahn () he mentioned it makes little difference to the life of a Lithium battery weather it is cycled shallow or deeper.
     
  11. sorka

    sorka Active Member

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    Yea, I've watched that video at least a half dozen times and have quoted it here just as many. Can you quote the time index for that statement?
     
  12. David99

    David99 Active Member

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    He didn't say it in this video. Someone contacted him and emailed with him and asked a few specific questions about charging patterns and what is better. One question was about the charge/discharge depth. He answered that it makes little difference. I found it somewhere in the Tesla Forum on Tesla's website. I don't have it bookmarked.
     

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