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Charging at 1/2, better or worse for battery life?

Discussion in 'Model S: Battery & Charging' started by rpavlicek, Mar 24, 2013.

  1. rpavlicek

    rpavlicek ***** Neophyte

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    Many days I have the option to charge or not charge the car when its around 1/2 (~100 miles on my 60kWh). I know the next day I'll probably only need 20-30 miles at most.

    I'm wondering if its better for battery life to let it get very low (20-30 miles remaining) or charge it back to full when its around 1/2 ...or does it make no difference?

    (The one reason I do charge it to full is for better acceleration :p)
     
  2. apacheguy

    apacheguy Sig 255, VIN 320

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    Shallow charge cycles are always better. Hence, plug it in even when SOC is 50%.
     
  3. mhpr262

    mhpr262 Member

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    Li Batteries should be charged as often as possible. Battery deterioration occurs because the graphite anodes in the battery physically swell up and shrink as they absorb and release electrons. It is this shrinking that causes microcracks and reduces capacity. So yes, as apacheguy has already stated, the charge cycles should be kept as shallow as possible.

    It's similar to the human body: You can gain and lose five pounds of bodyweight ten times in a row and will be none the worse for wear, but gain 50 pounds and lose them again all at once and you will be left with stretch marks and flabby skin.
     
  4. LuckyLuke

    LuckyLuke Model S P85DL

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  5. montgom626

    montgom626 Active Member

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    Always plug in your EV. Never pass up a chance to plug in an EV.
     
  6. sp4rk

    sp4rk Banned

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    Especially in public ... so the public can be more aware of it. :)
     
  7. Zextraterrestrial

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    Ok.

    so how about charging/ driving between say 100-130 miles rated for a 60 kW vs. being near the top for the 30 miles?
    or maybe between 160 - 190 on a 85kW vs ~205-235

    better?

    and I do public charge whenever I can but try not to charge at my house if I can avoid it (costs more even in off peak!)
     
  8. montgom626

    montgom626 Active Member

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    Plug in your EV whenever you have the chance.
     
  9. montgom626

    montgom626 Active Member

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    I understand the "cost" of power at home. Still plug in your car at home to 120V outlet and just reduce the charging rate to 2 amps/hour rate. Save money versus 12 amps per hour. You still have your car plugged in. It is a pittance of a charge rate, but it "protects" your battery by having some power going into the battery. It is only about a .1 to .2 kWh.

    I am curious, what do you pay for kWh? High and low.
     
  10. tezco

    tezco Sig P85

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    #10 tezco, Mar 26, 2013
    Last edited: Mar 26, 2013
    Charging at low amperate rates will probably cost you more at the meter since the coolant pumps and battery thermal management system may continue to run the entire time (also shortening their life). I believe there were some studies in the Roadster forum that show that charging at less than 20A on 240V lowers efficiency significantly. I charge at 20 or 30A (240V) and never do 100% range charging unless absolutely needed. #1 Enemy of LiIon battery is prolonged exposure to high heat. (Refer to Leaf battery degredation reports from Phoenix; however, unlike the Teslas, Leaf batteries don't have protective active cooling.)

    Prolonged SOC at 100% also shortens life; I wonder which is worst: 100% SOC state for long periods, or long periods at very low SOC. The car is set to keep the SOC in the 85 to 90% range since it will top off once a day when idle, after losing a few % of range. I assume Tesla figures this maximizes battery life as well as insuring that when you jump in the car you still have adequate range. So I just leave mine plugged in and let the management system take care of the periodic top-offs. If I need to leave it unplugged, I don't get too excited unless it starts to run into to a stretch of several days w/o a top-off.

    If I just run to the store and only use a couple of miles but plan to drive later, I don't bother plugging in either. But, if the SOC is less than 50%, I always plug in as soon as possible. (I estimate SOC by assuming 100% = about 300 ideal miles, so 50% is at about 150 ideal miles.)
     
  11. montgom626

    montgom626 Active Member

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    Tesla states to always keep the car plugged in. The HV battery is always at 85% charge if you select standard charge. I treat my MS like any other car. I don't worry about SOC. I just keep it plugged in. I try not to out think the engineers who built the car. The engineers know so much more about the car and how to keep it in the best possible condition. Similar to keeping the ICE oil level between low and full. I don't adjust the oil level based upon what I think is best, I just do what the manufacturer tells me to do.
     
  12. spatterso911

    spatterso911 MSP#7577 **--** MX#1891

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    How does this discussion change if you have timed charging on a TOU rate? Does the Model S still draw a slight charge outside of the timing window?


    Sent via Tapatalk
     
  13. Zextraterrestrial

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    haha... well, winter isn't 'too bad'

    For March i am paying $0.226 average (1446 kW)

    winter - partial peak baseline - $0.12 off peak - $0.10495
    > 200% - $0.32945 -$0.3131

    summer - peak baseline - $0.10070 partial peak -$0.17528 peak - $0.2872
    > 200% - $0.2872 -$0.38343 - $0.49535

    so 1$ ( with $0.25 back from Chargepoint for each session) per 6.3 kW is a pretty good deal - especially in summer + I get a nice walk


    and wrt to the trickle charge, I did the slow trickle a couple of times at first but I think the best charge technique is right before driving in the morning since it warms the car a bit while it is charging + regen is fully active when the temps are low.
     
  14. montgom626

    montgom626 Active Member

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    Darn, you pay some serious money for electricity!!! So, Chargepoint is much better deal. How far away is it???

    - - - Updated - - -

    I have not seen it draw any power outside of the timing window. If it does, it is very slight.
     
  15. Elshout

    Elshout Member

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    We who live in The People's Republic of California (Northern on Pacific Gas & Electric) are so used to getting ripped on our utility rates we are numbed to the effect on our wallets. During peak hours using Rate Schedule E-9 designed for EVs, over 300% of Baseline usage is at a laughingly low $0.58583/ kWh. On Rate Schedule E-6 rates go as high as $0.48653.
     
  16. tdiggity

    tdiggity Member

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    Agreed. I've been charging at public chargepoints that are 1 block from my condo for $1/hr, which works out to be about 16cents/kwh flat rate.
     
  17. Owner

    Owner Active Member

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    Yes but this seems like a bit "too much". How about having it just plugged in when you get home every day and have it charge at off peak times. Lets say someone gets home at 5pm, charges for a while on 110V or 5A on their 220, then sets the charge up again at 10pm at 40A? will they really be saving that much of the battery?

    Or will this kind of effort only apply when you return home and your battery is quite low? Say 50% or lower.

    but if you did a typical short trip of up to 30 miles, just wait till off peak hours?
     
  18. stopcrazypp

    stopcrazypp Well-Known Member

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    As long as you stay away from keeping the pack at or near 100% SOC for long periods of time, the SOC doesn't have a have a huge effect (diminishing returns). Like others have said shallow cycles are better.
     
  19. montgom626

    montgom626 Active Member

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    I agree. If I can, I always charge off peak. I assume that the grid is lightly stressed during off-peak. So everybody wins! Less cost to charge, less stress on the grid.
     
  20. neroden

    neroden Happy Model S Owner

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    Bleah! At those prices it's much cheaper to put up your own solar panels to generate your own electricity!

    Out here in the land of 11 cent hydroelectricity it hasn't seemed worth it.
     

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