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What should my ideal charge percentage be?

Discussion in 'Model S: Battery & Charging' started by Al Sherman, May 19, 2013.

  1. gavine

    gavine Petrol Head turned EV Enthusiast

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    I agree it can be confusing, but it seems like most people get it backwards....unless I only notice when it's wrong.
     
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  2. arnis

    arnis Member

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    It's confusing because absolute incompetence of what is being said.
    If one doesn't understand that Watt is a unit of power and Hour is a unit of time, then having voting rights is dangerous.
    A lot of power for a long time does a lot of harm.

    a*b=c Power*Time=Energy
    If you ride a bike (
    POWER) for an hour (TIME) you will burn a lot (kilo) of calories (ENERGY).

    kWh
     
    • Informative x 1
  3. brucet999

    brucet999 Active Member

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    How have you been able to determine 72kWh available in your battery? I know that I can display SOC as either % or rated miles. Is there a way to display SOC in kWh?
     
  4. Peter Lucas

    Peter Lucas Member

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    To calculate usable battery capacity, go to the Trips page and find "kwh used since last charge". Divide that by the change of SOC to get usable battery capacity. For example if you take a trip that brings the SOC from 80% to 30% and kwh used is 36 kwh, then 36 divided by (80%-30%=0.5) is 72 kwh. To get a reasonably accurate number you need to use a significant portion of the battery capacity.
     
  5. Busky99

    Busky99 New Member

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    Thanks for this great info about the percentage you should charge your battery - so easy to do with the slider - but I hav another question.

    "How often should I charge the car to the level set" (about 70% of max. ) since I know have the plug and charging cable in a super convenient spot right next to the car in my garage - I am kinda inclined to charge it up every night - even though sometimes I drive only 50+/- miles in a day.
     
  6. arnis

    arnis Member

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    Charge every night (drive at least 20% of charge). So if you use 10% per day, then maybe every second night.

    If you want to be green, charge at night only, very off peak :)
     
  7. Fiver

    Fiver Active Member

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    Just to build on this... I charge every few days, mostly try and keep my battery around the middle % of the pack. For my use case that means going from about 65% down to about 35% and then back up. Typically my battery is above 50% most of the time while sitting though since I don't drive that much. It's pretty rare for me to drive more then 15% daily. I'm lucky that my work location is only a few miles from where I live. I will set my slider at 50% and plug in even if my current charge is above that. I do this because if I do need more range, I can easily hop onto the phone app and bump up the charge limit. So even if I'm not charging, I do try and leave it plugged in just in case.
     
  8. arnis

    arnis Member

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    And if you charge, charge at elevated rates.
    Charging at really low rate runs coolant pumps for long time, contactors..also a lot of parasitic load - all is a waste of energy.
    minimum "OK" charge rate is 3kW. Though 60+% of onboard charger capability is optimal.
     
    • Informative x 1
  9. Gadget-X

    Gadget-X Member

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    Great thread. Quick question since I have not taken delivery of the MSP yet and haven't studied the manual. Can the percentage on the pack be changed remotely? I plan on keeping the battery in the 50-60% range unless I have a trip scheduled for the next day. I wanted the convince of changing without going to the car. I have the Tesla Gen 3 charger being installed.

    Thank you.

    M
     
  10. gavine

    gavine Petrol Head turned EV Enthusiast

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    Yes. The app has a slider for charge percentage. You can adjust anywhere from 50% to 100%.
     
  11. Gadget-X

    Gadget-X Member

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    TY sorry for being a novice but the app don't work until one get a Tesla...

    M
     
  12. Fierofiend

    Fierofiend Member

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    '14 P85DL here, latest software. Does anyone know at what charge % the coolant pumps shut off? I used to charge to 80% overnight, but now I wake up to 77-78% and the coolant pumps running 100%. Perhaps I need to set charge to only 75%? As soon as I open my door, and as long as I'm sitting in the car, they all drop to 25%. A few moments after closing the door when I exit, they will jump back to 100%.

    Also what about battery temp for them to shut off?
    It was 90* today, I have a 13 mile commute home. I was home at 6pm, my car is parked in an unconditioned attached garage. 3 hours later, my coolant pumps are still running 100%, my battery is currently at 38%.

    The funny thing is, when I plug in the charger (but isn't yet charging), the pumps drop back down to 25%.

    Am I to expect coolant pumps to just run all summer long now with these latest updates?
     
    • Informative x 2
  13. Gadget-X

    Gadget-X Member

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    #753 Gadget-X, Jul 15, 2020
    Last edited: Jul 15, 2020
    No expert but what you describe is crazy. I live in Florida. When I charge I don't hear any pumps. When I return to garage (90deg +) usually. Tesla only makes noise for about a minute or two then it shuts off. I always plug in as the manual says when returning from driving. I will observe a little closer....

    Is there some indicator that shows what pumps are running at?

    M
     
  14. Kenz

    Kenz Member

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    During the lock down.
    If you are not driving much lower the charge to 60% if that is more than enough for daily driving.
    It is better for the battery.
     
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  15. Gadget-X

    Gadget-X Member

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    On the 2020 that is a direct contradiction of what manual says.

    M

    battery2020.png
     
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  16. arnis

    arnis Member

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    When power electronics (and AP computer) are deactivated it doesn't make sense to circulate coolant for long.
    Below 50*C battery does not require "emergency cooling".

    You might have a software/hardware problem. Some transistors fail into "always on state".
    Also software upgrade procedures usually activate failsafe modes (cooling active until stated otherwise).
    Try reset.
     
  17. Fiver

    Fiver Active Member

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    Where does it say leaving the car at a 60% state of charge is bad for the battery? It makes no mention of what charge percentage, only to leave your car plugged in.

    I don't drive much these days. I leave the car plugged in, but my charge percentage slider is set to 50%. When I do go out I can charge at work, so most of the time I come home with well over 50%. I plug in, but at home the car isn't charging unless it drops below 50%.

    50%-60% is better for battery longevity if you don't need the range.
     
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  18. Araman0

    Araman0 Member

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    I can second what Fie is saying. My 2012 S85 trickle charges in our garage, and the whole time it's plugged in (even if the batter reaches the 80% limit) the coolant motors keep running. The only way to stop the coolant system from running is to unplug the car. I can imagine it's a huge waste of electricity and probably wears out the coolant components pretty fast too.

    Here in Seattle the days rarely get above 75 and nights (outside the garage) are in the 50s.
     
  19. Dave EV

    Dave EV Active Member

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    Elon has tweeted that ideally, you cycle the battery around 50% for optimal longevity when in use.

    For storage, the lower the SOC the better. There are studies that show that you lose the least capacity by storing the cells at 0% SOC! This is not practical because there is some self-discharge, but you can take this to mean that if the car's just going to sit there, let it sit there at low SOC, and then recharge it just before you need the range. Check out the graph in this post (there's a lot of other information in this thread, too): Battery Improvements - Pieces of the Puzzle

    My recommendation for COVID times if you're working from home and just have the occasional trip to the store? Charge to 50% when you need to recharge, leave it plugged in until you need to drive, then recharge back to 50% when you start getting range anxiety. For me, this is 30-50% SOC right now. If you prefer to leave it plugged in as much as possible, do that, but still leave the SOC set to 50%.

    The 85 kWh Model Ss are unique, as a not-so-recent firmware update causes the coolant pumps to run until the SOC drops to 77-78% SOC or so. Drop your max charge to 70-75% and you should be able to just leave it plugged in. This is discussed in this thread if you can find it: Sudden Loss Of Range With 2019.16.x Software
     
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  20. Gadget-X

    Gadget-X Member

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    Well if all that were true (not saying it is not) why not put it in the manual. If their batteries lasted longer then they would make more money. Wondering if you did 50% and pack went bad if you voided warranty by NOT following manual operation instructions? You know the huge amount of data they collect.

    M
     
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