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What Charging Methods Minimize Degradation?

Discussion in 'Model S: Battery & Charging' started by internauts, Oct 1, 2014.

  1. internauts

    internauts Member

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    I am interested to hear opinions about which charging methods are best to prolong battery life (reduce battery degradation). I found many suggestions, but have not found these questions discussed elsewhere. For each question, the amount of charge is presumed the same.

    1. If a person's daily use is a small portion of range, and leaving each day with a full range is not needed, should they charge daily or occasionally?


    Charging from 75% to 90% every day, or​
    charging from 30% to 90% once every four days?​

    2. If a person has 80-amp HPWC available, should they choose to charge more slowly at 40-amps when there is no need for faster charging?


    Charging at 80-amps for 2 hours, or​
    charging at 40-amps for 4 hours?​
     
  2. AmpedRealtor

    AmpedRealtor Active Member

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    It's probably more efficient to charge at 40A. At 80A the HPWC throws out a lot of heat in the cord and handle (waste), and the car's battery cooling system kicks in (more waste) which is current that is not going towards charging. Here in AZ, I have dialed down the HPWC to charge at 40A during the summer.
     
  3. Canuck

    Canuck Active Member

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    90% is probably outside of the daily driving range. Keep it in the middle of the daily driving range unless more range is needed. You don't want to go too low or too high and you do want to keep it plugged in when not driving...

    ScanSep2201311_40AM-page1.jpg
     
  4. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I have an HPWC with 80 Amp capacity. I set the current limit to 56 Amps. That cuts the resistive power in the wires, and each of the dual chargers, in half. 56 Amps is the geometric mean of 40 and 80 Amps and good compromise. Also, it uses both chargers, testing both each charge so that you know they both work.
     
  5. breser

    breser AutoPilot Nostradamus

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    My HPWC doesn't get hot at all at 80A (slightly warm yes). There's a thread, it seems there are some problematic HPWC cables/plugs and if yours is getting hot you should get it checked.

    I'm not convinced that you're avoiding much with the cooling system by a slower charge. As you get closer to a full charge there is more resistance in the battery which gives you heat. So the question is is the heat from the resistance of the wires putting 80A instead of 40A more than the heat losses of the resistive nature of the battery as it gets fuller and you need to charge for twice as long? That's not an easy one to answer and I doubt anyone has any idea.

    Someone with the ability to meter the exact power that the car is pulling to go from the same low SOC to "full" SOC could probably help answer this, but it's rather hard to get the car into the exact same low SOC.
     
  6. hiroshiy

    hiroshiy Active Member

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    Will there be any difference between 90% and 80%?
     
  7. brianman

    brianman Burrito Founder

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    @Amped, @Cotton, and @breser

    The question was about degradation, not from-wall efficiency. Unless I misunderstood.
     
  8. TexasEV

    TexasEV Active Member

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    Charge daily and don't worry about degradation. As long as you don't leave it at 100% frequently the difference isn't worth thinking about. Regarding 40A vs. 80A, that's 10kW vs. 20 kW. With supercharging being 120 kW, it's unlikely there's going to be a significant difference between 10 and 20 kW. You don't need to overthink this. Just plug in and enjoy.
     
  9. Rockster

    Rockster Active Member

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    I charge at 42 amps for the same reason.
     
  10. breser

    breser AutoPilot Nostradamus

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    You didn't. Though the heat created from charging faster may be a degradation issue. What I was driving at and got somewhat sidetracked into the efficiency bit is that it's not clear if 80A that makes the battery slightly warmer for less time could be better than warmer for longer at 40A charging. The resistance of the battery as it gets fuller drives heat not just charging rate. There's a study someplace that suggests faster charging isn't bad on Lithium Ion batteries, it's been linked in other threads around.

    Yup, I tend to agree with this. I have a hard time seeing how 80A could be bad when Tesla doesn't discourage people from supercharging when it isn't necessary.
     
  11. RiverBrick

    RiverBrick Active Member

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    +1

    Charge from 35% to 50% daily if you're really sure you will not need extra range on short notice.

    More importantly, as much is practical, avoid charging when the battery is extremely hot or freezing. In such cases, the car will protect itself by limiting the current and activating the battery's temperature management system. However, you can help a bit by judicious timing of charging sessions.
     
  12. invisik

    invisik Member

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    My daily commute to my office is about 4 miles. I charge to 60% at night (about 157 miles or so). Gives me plenty of extra miles if I have to go to a client meeting or something. If I need more later, I'll charge again at home or at work.

    I believe it says to charge the car to meet your daily driving needs. Staying a little lower on the charge limit should help battery life (see battery university post elsewhere)

    -m
     
  13. ch_model_s

    ch_model_s Member

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    PastedGraphic-1.jpg

    yes down to 50% less is better. thats why the charge slider only goes down to 50%. for storage as example plug your car in and set the slider to 50%.

    a simple rule is just charge as much as needed. you can see it in the graph from an german engineering magazine the last 10% are the worst. (second graph LiCo, y-axis is degradation and x-axis SOC)
    charging:
    the prof of this video http://www.teslamotorsclub.com/showthread.php/27109-Why-do-Li-ion-Batteries-die-And-how-to-improve-the-situation
    said somewhere to charge at c/2 which is not possible at home. so charging at 80amps or 32 3-phase is the best for battery life because charging stresses also your battery and with that charge speed the charging time is lower. and you should set the timer so that charging is finished bevor you start driving to minimize the time at high SOC.
     
  14. UberEV1

    UberEV1 Member

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    Off Topic: The previous post inspired me to compliment all our fellow forum members for whom English is a second language. The Tesla community is growing quickly in non-English speaking countries, and the participation in these forums and fluency in English are both fantastic. I admire anyone who can communicate well in multiple languages, mostly because my own attainment of that goal is limited (a bit of French and German, but certainly not fluent). So, my compliments to all those who already participate and a voice of encouragement to those who may otherwise be too shy - we are truly a global community now!
     
  15. internauts

    internauts Member

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    My conclusions from the answers here and from the forum link (that was great information):


    Daily charging is best. No apparent increase degradation due to frequent charging; no advantage to charging every four days.


    Charging to a lower number, ideally that 4.00 V level, which someone estimated is 85%, is best. Since 80% will be more than triple daily needed range, that will be my target unless a longer trip is planned.


    The maximum 80-amp charging rate will cause less degradation.
     
  16. X-RAY

    X-RAY Member

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    Why is 85% (4.00 Volts) the best you say? I was under the impression that 50-60% SOC was the best SOC for the MS to 'live in'.
    Occasional repetitive 100% cycles might be needed to rebalance the cells. At least that is what I filtered out of the above video...
     
  17. David99

    David99 Active Member

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    Is there any official info from Tesla saying that?
     
  18. djp

    djp Roadster 2.0 VIN939

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    As described in the video, lower SOC is better for battery life, with 4.1V being better than 4.2V, and 4.0V better than 4.1V. Storage mode on the Roadster is about 20% SOC. There's a tradeoff between battery life and useable range, which is why Tesla recommends charging to what you need.
     
  19. internauts

    internauts Member

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    I think I will use 80% as my every night level, unless a range charge is needed. Two reasons. The video and other sources say 4.00 volts is where the bad reactions begin higher levels. My wife and I will be more comfortable beginning a day with 200 miles in the battery. That is about half of the distance we would get from an ICE full gas tank. At 1/4 tank, my wife has to refill. The information I have found leads me to the conclusion that there is no significant degradation difference between 50% and 80% charges.
     
  20. AmpedRealtor

    AmpedRealtor Active Member

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    Why? Sources?
     

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