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Charging while car sits

Discussion in 'Model S: Battery & Charging' started by Alysashley79, Jan 1, 2015.

  1. Alysashley79

    Alysashley79 Member

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    Does anyone know exactly at what point the car will start to charge again when it's plugged in and sitting and not being driven?

    Ie: the car is set to charge to 90% it's plugged in but just sits plugged in, in the garage for four days. The car fully charged to 90% and then just sits plugged in. Because it's in the teens here I lose anywhere from 5-7 miles of rated range per night

    at what point "should" the car start to charge again to top off back to 90%.
     
  2. NigelM

    NigelM Recovering Member

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    Every 24 hrs.
     
  3. NOLA_Mike

    NOLA_Mike Active Member

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    Mine tops off once every 48 hours.
     
  4. strider

    strider Active Member

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    I know that is true if you have a charge time set but does it also apply if the car is set to charge on plug-in?
     
  5. NigelM

    NigelM Recovering Member

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    I'm pretty confident about saying "yes" to that question; although NOLA_Mike (see his post above) may prove me wrong. I've had my car on a set charge time for a year or so and I'm working from memory.
     
  6. mknox

    mknox Well-Known Member

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    If you have a timer set, the car will respect that and only do its top-off at the time set. Otherwise, in my experience, it seems to top up when it's down about 2.5 kWh from the set point. I have a power meter on my EV circuit and when I'm away, whenever it tops off it's almost exactly 2.5 kWh each time. With earlier firmware, that happened every other day while the car sat. Now it seems to be a bit more random. Sometimes it will top off every day and other times it might sit for 3 days before it needs to charge.
     
  7. NOLA_Mike

    NOLA_Mike Active Member

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    And mine is not on a "time of day" charge - it starts charging as soon as I plug it in. When I let it sit for days at a time (like i recently did with my soon to be traded in P85+) it would top off about every 48 hours.

    Mike
     
  8. Alysashley79

    Alysashley79 Member

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    Thanks everyone.

    Mine sat for 4 days. 90%SOC I get about 231 rated miles and after 4 days I was down at 207. It's not set on a scheduled charge (well it is NOW) but wasn't at the time. I was a little surprised at how much it had dropped and when I called the SC they didn't really know.

    For or now I've got it scheduled to charge just song have a nice warm battery when I leave in the mornings now but good to know that it'll also kick on daily if the timer is set.
     
  9. thecloud

    thecloud As rhythm raced inside, the ship came alive

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    I doubt it will kick on daily just because the timer is set. Pretty sure the SOC needs to drop by some amount before it will perform another charge cycle. As a point of comparison, mine is scheduled to charge daily at 2 AM. On a few occasions I've left the car plugged in for several days at a time without using it, and have noticed that the first charging cycle always completes as expected, but on subsequent days at 2 AM, no charging occurs. My experience with "vampire drain" is similar to yours, but with the car plugged in the entire time and set on a scheduled 2 AM charge.

    mknox observed that a -2.5 kWh loss could be the magic value that triggers a recharge. I could do some science by leaving the car plugged in continuously for days, recording charge levels. But then I wouldn't be driving the car, so that wouldn't be any fun! :)
     
  10. Alysashley79

    Alysashley79 Member

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    +1. This is the first time in over a year she hasn't been driven at least once a day and it was only because I was sick and kids are out of school!
    You don't get 37,000 miles in 13 months by not driving!
     
  11. mknox

    mknox Well-Known Member

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    That's what I have observed. Prior to 6.0 it would charge every other day to the tune of about 2.5 kWh starting right at my timer setting time. Since 6.0, it still starts up at the timer setting time, but may be every day or it may sit for 3 days before charging. I no longer get the consistent 48 hour cycle.
     
  12. HankLloydRight

    HankLloydRight Fluxing

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    Mine sits without a timed charge, and starts charging when it gets between 5 and 10 miles below the prescribed charge limit (currently about 200 miles). For me, it's definitely not 24 or 48 hours.. it's whenever it drops a fixed amount to "top up" to the prescribed limit.
     
  13. Blu Zap

    Blu Zap Grinning member

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    The vampire drain on my P85+ causes it to charge every night at the time set. I lose 5-7 miles a day just sitting in the garage. It recharges every night at 11:00 pm, when the PG&E rates drop.
     
  14. Knobby

    Knobby Member

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    Well I am frequently away and I leave it plugged in with the charge limit set at 50% and time set for 11:00 pm and I've observed its behaviour extensively. It will top up when it loses 2.5kwh. Or ~13.35 km or 8 miles below the charge limit setting. At rated energy consumption of 188 wh/km, 13.25 km is 2.5kwh. In energy saving sleep mode that's 2 days usually, sometimes 3. It does respect the time of day that is set. So every 2 or 3 days at 11:00 pm I see it top up for about 22 min (at 32 amps). 32A*240V*(22/60)h = 2816 wh. Times some efficiency, say 88% = 2.5 kwh. Makes sense. It is very consistent.

    Of course if you set the charge limit lower than you normally set it at for daily use then it may take many days, even weeks to discharge to the point that it is 2.5kwh below the new charge limit.
     
  15. tezco

    tezco Sig P85

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    Mine can go for a few days before topping off. I suspect that as your 12V ages, it becomes less efficient and probably requires more frequent top- offs, which may explain why some cars top off from the wall more often. Also, some say that leaving the app running on your phone keeps the car from going into deep sleep, so I always close the app when finished.
     
  16. Dborn

    Dborn Confirmed

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    I was under the impression that once plugged in, even on a timed charging time, that the car would preferentially draw from the mains, and so there should be zero vampire drain. From the discussion above, this seems not to be the case.
     
  17. mknox

    mknox Well-Known Member

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    Precisely what I observe now on Firmware 6 myself. Prior to 6, I'd see the 2.5 kWh top off exactly every other day.
     
  18. Alysashley79

    Alysashley79 Member

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    There ARE vampire drains! Even on the brand new loaner 85 I had it experienced vampire losses. Tho it's quite cold this time of year not getting Bove freezing here for the past week and in the 20s at night. So vampire losses are likely exaggerated because of the cold.

    Now ow as far as when the car is plugged in and drawing from shore power. (The wall) if you preheat your car Eric then that will come from shore power vs the car.
     
  19. mknox

    mknox Well-Known Member

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    Nope. The car will draw down the battery, then top up from shore power when the battery is down by (I believe) 2.5 kWh or so from your slider set point. If you turn on HVAC via the app or by getting into the car when plugged in, it will draw shore power.
     

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