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Preserving battery life: short or long charges?

Discussion in 'Model S: Battery & Charging' started by Right_Said_Fred, Sep 26, 2012.

  1. Right_Said_Fred

    Right_Said_Fred Model S - Sig. 283 EU

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    As more and more people are taking delivery of their Model S, I was wondering what is the best way to preserve battery life. If you have a daily commute of, say, 2 x 30 miles you could drive to work for 4 or 5 days before you need to recharge. Is that the best choice? Or is it better to topp off the battery: short charges every time you get to work and again every time you get home?

    I've read in the past that a battery can handle only a certain amount of charges and discharges (no idea if this applies to the Model S battery). I wonder if a small charge/discharge has the same effect on battery life as one full charge/discharge?
     
  2. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    TM has consistently said that the best way to keep the battery in good health is to keep the car plugged in when not in use. There is no benefit in letting it reach a low level before recharging, probably the opposite.
     
  3. augkuo

    augkuo Member

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    The best bet is to keep your battery at 50% - charge enough (but not fully) before you go to work and before you go home so that your average state of charge is 50%. For example in the 300 mile range S, you'd charge up to 165, drive 30 miles (down to 135) and charge back up to 165. Also keep your battery out of extreme temperatures and minimal flooring of the accelerator ;)
     
  4. strider

    strider Active Member

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    Battery life is typically stated in number of full discharge cycles. So 1 charge from 0-100% or 2 charges from 50-100% equal 1 cycle. So you're not cheating anything by charging it fewer times. Just leave it on standard mode and charge every night. Tesla will take care of the rest.
     
  5. Right_Said_Fred

    Right_Said_Fred Model S - Sig. 283 EU

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    Better not getting the Performance then :rolleyes:

    Thanks for all the answers!
     
  6. dsm363

    dsm363 Roadster + Sig Model S

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    Tesla recommends plugging it in each night for a standard charge. There isn't even a storage mode in the Model S anymore.
     
  7. Sparrow

    Sparrow S105/ Roadster 189

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    Of course these batteries are continually changing. Old school for lithium batteries is that they like to sit at 40 to 50% SOC, but they take discharge better at higher SOC. For that reason I set the timer on my Leaf to finish around the time I will first need it each day. Since I don't commute to work, that first drive tends to be within a 4 hour window in the morning. Anyways my goal is so the car doesn't sit at a high SOC all the time, but also so that I don't drive the car at low SOC much. To me this means charging to the 80% or so and then not driving it below 30 or 40% often. I don't worry about the occassional full charge and deeper discharge as long as most of my charging and driving fits my above stated pattern. Of course the difference with the S, is that the daily driving I will do in it (about 30 miles per day) will be similar to the Leaf, but the S has 4 times the range. I'll probably charge the S twice a week. If I were doing 60 miles a day in an S, I would charge at least every other day. My wife has severe range anxiety so she charges our Roadster everynight for her 54 mile commute and the couple of times that charging didn't occur over night, she has driven our ICE Minivan instead. I know everyone has their own theories and I still suspect that most of the reason Tesla wants you to charge it everynight is so that you don't foregt to charge it and not have enough range for the next day.
     
  8. contaygious

    contaygious Active Member

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    If my commute is only 4mile each way is it really worth plugging in every night or are weekends fine?
     
  9. dsm363

    dsm363 Roadster + Sig Model S

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    It's worth plugging it in I think if you park in a garage and have the charge cable sitting there. That's what Tesla recommends so probably worth doing. If you don't have good charging at home then maybe charging once a week would be ok.
     
  10. smorgasbord

    smorgasbord Active Member

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    Roadster owner collective wisdom:

    1) When they talk about "cycle life," the definition of a "cycle" is the capacity of the battery. So, driving until the battery is empty and then charging is one cycle, as is driving until the battery is half-empty and then charging two days in a row. That said, two half-cycles are easier on the batteries than one full-cycle since you don't want to have the battery almost empty very much nor very long.

    2) When you "top" off the battery in Roadster or Model S and are NOT in Range mode, you're not really topping off, so there's no problem keeping the charge there.

    3) Charging after every drive cools the battery, and keeping batteries cool extends their life.

    Bottom line is generally to plug-in and charge after every drive.
     
  11. Eberhard

    Eberhard #421 Model S #S32

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    yes, but you should daily charge in "storage mode" this would save the battery most.
     
  12. dsm363

    dsm363 Roadster + Sig Model S

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    The Model S doesn't have a storage mode though at this point.
     
  13. Doug_G

    Doug_G Lead Moderator

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    Storage mode can be effectively emulated by not plugging in at all! It won't do anything at all until the car is below 30%. It will also result in your battery going out of balance. Needless to say I disagree with this advice.
     
  14. contaygious

    contaygious Active Member

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    I have a garage and cable, but it just doesn't seem very convenient to charge every night when I only drive 8 miles each weekday. if I want the battery to stay around 50% then wouldn't about once a week do a better job at this?
     
  15. dsm363

    dsm363 Roadster + Sig Model S

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    It literally takes 5 seconds to plug in and becomes a habit and no big deal. As Doug_G said, the car probably won't balance unless it has a standard charge so trying to time things to hover around 50% is probably more trouble than it is worth and not gaining anything. As mentioned above, Tesla recommends plugging it in each night so probably the way to go.
     
  16. jerry33

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

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    The smaller the charge cycles, the more charge cycles you can have--assuming that you're normally not charging from the very bottom or to the very top of the battery's SOC. Some example (but made up) numbers:

    0% to 100% charge = 300 cycles

    50% charge = 36,000 cycles

    25% charge = 1,200,000 cycles

    10% charge = 430,000,000 cycles

    This is why hybrid cars' batteries last longer than BEV batteries even though they are much smaller in capacity. So if you had the 85 kWh battery, drove 12 km each day and did a standard charge every day, the battery would last a very long time and would probably fail due to the age of the chemistry or corrosion rather than the microcracking which is what typically causes batteries to fail.
     
  17. onlinespending

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    Just because Tesla recommends that you plug it in every night doesn't mean that's the most optimal condition to preserving battery life, which is what the OP is asking. Tesla recommends topping it off every night mostly because it's convenient to do so, and the last thing they want to be telling their customers are some complicated directions like "Try to keep the battery level between 40% - 60% if at all possible". Remember, an EV should be painless and easy to use, otherwise it could scare people away from adopting the technology over what they're used to.

    Plus there's a reason why they have a standard charging mode that only goes to 85%. Clearly that's advantageous for battery longevity versus consistently fully recharging it to 100%. So the question is, would it be even more advantageous to limit a recharge to say 50%, if you know you're driving habits would allow you to do so most times? For most users, they'll want to follow the simple and straightforward recommendation of topping it off completely each night. But for those of us that don't mind the slight inconvenience of limiting the charge to some lower %, we're looking for the best practices to preserve our battery (however minimal those advantages might be for battery life).
     
  18. jerry33

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

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    My understanding is that although it's easier on the battery to charge between 30% and 50% but it's also easier on the battery to drive between 85% and 50%. Because driving transfers more energy from the battery (over a given amount of time) than charging, I'd say that a standard charge daily is better for the battery than only charging to 50%.
     
  19. KenEE

    KenEE P1937 Reward Excellence!

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    What about speed of charging? Is it better to charge nightly for say 8 hours at 10-15 Amps or 2-3 hours at higher amps?

    I know I can buy the wall charger and just leave everything at default. (that's what we do with our Volt)
    I'm wondering if I would gain a few percentage points over 4-5 years if I charged more slowly or say plugged into 110 instead of 220.

    I'll typically drive 20-40 miles per day with the occasional 100 mi (across town) and the occasional 200+ mi out of town trip.
     
  20. aviators99

    aviators99 Model S - R140

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    Good question. I was at the Tesla Store on Wednesday (I hang out there now, trying to be as much of a squeaky wheel as possible), and I watched a demo where the sales guy said that if you want the battery to last longer, keep the amps lower. Until then, I hadn't seen the "dial" where you could limit the amperage going into the car below max from the 17" screen. Does it really make sense to do that? I will have an HPWC.
     

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