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Best way to charge for battery health?

Discussion in 'Roadster' started by Pantera Dude, Mar 18, 2012.

  1. Pantera Dude

    Pantera Dude Member

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    #1 Pantera Dude, Mar 18, 2012
    Last edited by a moderator: Sep 3, 2012
    What is the recommended way to use the battery? Should it be fully charged every night or is it preferred to run them down to 20% or so before charging? I'm thinking that if I am only using say 25% of the battery's charge on a normal day, that would only require 6 or 7 hours per night to charge it with 110, am I correct about that? I guess I could start off going the 110 route and then spring for the 220 if I'm not happy. Is the battery life compromised in any way by using the 110 instead of 220?
     
  2. TEG

    TEG TMC Moderator

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    #2 TEG, Mar 18, 2012
    Last edited: Mar 18, 2012
    Many of your battery questions are debated.
    What I recollect:
    Recharging/topping off after short trips is good. Letting it go down to 20% on purpose is not so helpful. But, charging to 100% is not so great either. If you charge in "standard mode" (instead of range mode) then it doesn't fill to 100% so you are in good shape.
    So, basically - leave it plugged in whenever possible in a "standard mode" charge.
    "Range mode" or "Performance mode" should be saved for special occasions, and it is best to time it so you use the car right after one of those "full" charges. Also, best not to do "Range mode" or "Performance mode" charges on a really hot day.
    There really is little/no "memory effect" so letting the pack run down by missing charging opportunities isn't really useful.
    Charging from 120V is somewhat wasteful as a relatively higher percentage of the electricity is used running accesories and charging equipment and less makes it into the battery pack than you would get if using 240V.
     
  3. Doug_G

    Doug_G Lead Moderator

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    The important take-away from TEG's message is: Plug it in every night and charge in Standard mode.
     
  4. NigelM

    NigelM Recovering Member

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    +1

    Pantera, sounds like I'm in the same situation as you....There are days when I drive 5 miles and days when I drive 150 miles. I've discussed it with several Tesla people and they all told me: "Plug it in, regardless of miles driven" Over time, the battery pack will balance itself just fine. The only caveat is that if you're not going to drive for a few weeks,still plug it in but change to storage mode.
     
  5. Pantera Dude

    Pantera Dude Member

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    Sounds good, thank you!
     
  6. Timothy

    Timothy Driving on Sunshine

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    My understanding from talking to some of the guys at Tesla that plugging in every night is not necessaryand not helpful. I've been told to plug in once the battery is 50% discharged. I usually drive about 100 miles per week, so I charge every Sunday night.
     
  7. TEG

    TEG TMC Moderator

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    Yeah, keeping above 50% is probably good enough. (Although if you had some unexpected emergency, you might have wished it was left plugged in.)

    There are still some people who got "trained" from the Ni-Cad days to think you are supposed to drain your battery before recharging.
    Probably not such a good procedure for Li-Ion. I think it is "happier" if you never let the SOC get very low.
     
  8. dsm363

    dsm363 Roadster + Sig Model S

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    They have always recommended keeping it plugged in when you are not driving. That could be just so if you forget it's not left at a low SOC but it's not supposed to be harmful charing every night in standard mode according to Tesla. I guess it could be better for it to stay at 50% SOC but it's easier to just plug it in each night.
     
  9. Pantera Dude

    Pantera Dude Member

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    Thanks guys!
     
  10. hcsharp

    hcsharp Active Member

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    That depends on where you live and how you drive. While keeping your SOC high all the time has a minor impact on battery life (minor because it's never above 90% in std mode), there are other factors resulting from not charging every day that can impact it more. Heat and high amperage draw are worse for the battery than leaving at 90% SOC. If you drive with the same speed and acceleration at 50% SOC as you do at 90%, it will draw more amps and heat up the battery a lot more. If you never drive the car very hard then this may not be much of an issue.

    The other issue is extreme cold or hot weather, which you don't have in Santa Barbara. Storing the battery at a high SOC while it's cold has almost no impact on its life. But driving in extreme cold is hard on it, especially at a low SOC. If you keep it plugged in then it never gets so cold that it's affected by this.

    And to add to what TEG said, it's nice to be able to dump the gas-car model that you're used to. Charging every day is ultimately more convenient because it's always full for unexpected trips.
     
  11. Timothy

    Timothy Driving on Sunshine

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    Hrumpff! It does SO get cold here--42 degrees one night earlier this week! :) (But 70 in the daytime.) For me, unexpected trips are always expected, so I can charge extra if I need to. But once a week works great 95% of the time and I rarely get below 50% SOC.
     
  12. vfx

    vfx Well-Known Member

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    Agreed on this Timothy. Word from battery engineers at the factory (somewhere in these pages we have a quote) is plug in every night.
     
  13. dsm363

    dsm363 Roadster + Sig Model S

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    There have been a few owners charging in standard mode for 3 years now with very little drop in ideal miles after a charge. It really is better and a good habit to just plug in when you get home. Even if I'm going going to be home for a few hours I still plug in. That way I rarely forget.
     
  14. Doug_G

    Doug_G Lead Moderator

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    You mean +42? How about -42???
     
  15. TEG

    TEG TMC Moderator

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    As you may have noticed, some have contradicted that somewhat saying that nightly top-off (in stanard mode) is preferable.

    I was just noticing this:
    Model S Facts | Tesla Motors
     
  16. hcsharp

    hcsharp Active Member

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    #16 hcsharp, Mar 22, 2012
    Last edited: Mar 22, 2012
    The cathode in Li ion batteries forms defects (microcracks) due to stress caused by expansion and contraction relative to neighboring materials. It is simply bigger or smaller depending on whether it's charged or discharged. The more you discharge it, the more it changes size. And the more it changes size, the more microcracks it gets. These microscopic cracks lower the battery's capacity. That's one reason why smaller cycles, more often, contribute to longer battery life. That's why you should plug it in every night.

    Heat aggravates the microcracking process, so keeping your battery cool contributes to longer battery life. And guess what? Your battery heats up more when used at a lower SOC because it requires more amps to keep your car going 65mph than it does at a higher SOC. That's why you should charge it every night.

    Capacity fade also comes from the build-up of non-soluble deposits on the anode and cathode. This chemical process happens faster when the battery is warmer. It also happens faster when at a high SOC. But the process slows to a crawl when you drop the SOC to 80 or 90%, and slows only a tiny bit more at 50%. So if you are going to drive your car, keeping it charged in std mode has less impact on battery life (lower amps, less heat) than driving at a lower SOC. But if you're not going to drive your car for a few days, there are no amps or heat to worry about. That's when Tesla recommends putting it in storage mode, which keeps it at a lower SOC.

    end of science lesson.
     
  17. bonnie

    bonnie Oil is for sissies.

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    Wow, thanks. That is the best explanation I've heard on this, by far.
     
  18. Timothy

    Timothy Driving on Sunshine

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    Too much science for a non engineer! But if you live in a temperate place (my house has a weather station and the low in the last year was 40 [yes, plus 40!] and the high 87--though never that high in my garage) and you drive 10 mi avg a day and charge in standard once a week (sooner on the rare instance I drive longer and get a SOC under 50%) is it STILL worth charging daily? I have had the car 11 months and there has been ZERO drop in the range after a standard charge since day 1. Not that it is that big a deal, but it is somewhat of a pain to plug it in daily if I really only need to do so once a week!
     
  19. hcsharp

    hcsharp Active Member

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    #19 hcsharp, Mar 26, 2012
    Last edited: Mar 26, 2012
    @Timothy: Most people setup their chargers so it's not a pain to plug it in every day. Takes about 5 seconds generally. When I first got my Roadster I treated it like a gas car for a couple of weeks like you are doing. Eventually I realized the electric paradigm was better for battery life and more convenient. If you want to keep doing it the way you are, I'd drive gently when the battery gets down near 50% SOC.

    My elderly parents live in Santa Barbara. My mother was an organic avocado rancher for many years. The climate is quite nice! I'll bet some of those roads like Mountain Dr and Gibralter Rd are fun in a Roadster.
     
  20. dsm363

    dsm363 Roadster + Sig Model S

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    Tesla recommends plugging it in every night so that is what I do. If that was detrimental to the battery, they probably wouldn't recommend it.
     

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