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Battery and cabin heating included in Wh/km?

Discussion in 'Model S: Battery & Charging' started by Doubletap67, Dec 25, 2016.

  1. Doubletap67

    Doubletap67 Member

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    I've searched and read many of the longest (and oldest) threads on TMC related to cold weather range, and haven't seen the explanation for what I'm seeing...

    I've had my 60D for a few days (and love it) and have had mostly 20 km and shorter drives - it's been unusually cold for Vancouver ( 0°C and below for many days in a row) and although I've got a HPWC I haven't been consistently preheating so I'm assuming that a lot of energy is going to battery and cabin heating at the beginning of my drives. What I'm not understanding is that I'm getting an average of 230 Wh/km (which seems okay in these conditions) but my battery percentage is dropping faster than accounted for by Wh/km alone. According to TeslaFi, for 18.37 km driven last night at 200 Wh/km I used 7% of my battery (3.68 kWh). Either my battery is 52.6 kWh usable (and not 62.4 as recently discussed in recent threads), or battery and cabin heating is "hidden" and not included in the Wh/km consumption data. That would be okay and manageable, but seems to be contradicted in other threads where members state their cold weather consumption in terms of 30% greater Wh/km.

    Would really appreciate someone pointing out where I'm confused.
     
  2. scaesare

    scaesare Well-Known Member

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    The cabin heating energy use should be reflected as long as the car as in drive. It appears that if the car is parked, that usage is not accounted for in those displayed numbers.
     
  3. ColdRauv

    ColdRauv Member

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    Excellent question! I, too have wondered and I'm convinced that the energy used to preheat, or heat the battery is not included in the Wh/mi calculation. I believe that only when the car is in drive does the calculation start. I agree that the battery in cold weather drops miles much faster than the cluster indicates, due to heating.
     
  4. jerry33

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

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    If you are plugged in the power for preheating comes from the wall (strictly speaking it charges the battery just enough to maintain the same SOC).
     
  5. Doubletap67

    Doubletap67 Member

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    Thanks all for the input so far.

    Yup, makes sense that the cabin and battery heating is counted when the car is in drive, but that doesn't explain where all the battery capacity went in the example drive above. I start with 350 rated km, consume at 200 Wh/km, but end up further down than distance times consumption. Makes things less predictable than I expected.
     
  6. jerry33

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

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    1. Wind (any wind that's not from behind increases power demand).
    2. Tire pressure (lower when cold, compensate by increasing the pressure).
    3. Rain or snow (has a dramatic effect on power used).
    4. Air density (cold air is denser and so is harder to push through).
    Basically, don't rely on calculations. Instead, start slow and watch the trip graph to see how you are doing compared to the estimate. Speed up or slow down as appropriate.
     
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  7. Doubletap67

    Doubletap67 Member

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    Won't all of the above show in Wh/km though?
     
  8. boonedocks

    boonedocks Member

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  9. jerry33

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

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    When you are stopped, the heating won't.
     
  10. Naonak

    Naonak Member

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    Is there any evidence that heating power is calculated into the display, even if in drive? It would seem to me, that value comes from how much power flows through the motor(s) vs the distance traveled... so even in drive, the power is not accounted for. At least, that's the way I've always believe it behaved, but I've never explicitly tested it.
     
  11. Doubletap67

    Doubletap67 Member

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    I had the energy consumption graph pegged to the top for two or three minutes last night after returning to the car (outside in wet snow) after about three hours. I assume this was some kind of high energy consuming heating cycle. Consumption was around 600 Wh/km I think, even though I was just driving at a crawl through a parking lot.
     
  12. David29

    David29 Member

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    I can't imagine that is correct, because if it were, those of us in cold climates would not see such remarkably higher energy consumption figures in cold weather. It is not just that the battery SOC drops faster, it is the displayed energy use and average wH/mile that are higher in winter.
    But like the OP, I have also puzzled over just what energy use is considered in the car's calculations. If it ignores energy consumed when not in Drive (or reverse as well maybe?) then that could make sense but I also have not seen a definitive answer.
    But clearly the battery SOC figure (or range) inherently reflect all energy used.
    It does seem to require some careful testing and bookkeeping to demonstrate conclusively how the car tracks and displays energy consumption.
     
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  13. David29

    David29 Member

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    If I understand correctly, this is only partially true. In particular, I understand from other posts here that the battery heater and the cabin heater are each rated at about 6 KW when run at full power. When preheating, the car may need to draw some power from the battery if the charging current is less than what is required to heat both the battery and the cabin. A 40-amp charger (at 240 V in the US, single phase) provides only about 9.6 KW. So if both the cabin heater and battery heater are running at full power, some power may be drained from the battery, at least temporarily until the heater power gets ramped down. To power the full 12 KW, you would need 50 amps at 240 VAC. So either the newer standard charger of 48 amps (11.5 kw, or close enough for discussion purposes), or dual chargers in the older cars, would provide enough to run both heaters at full power.
     
  14. JRMW

    JRMW Member

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    I don't know if this helps...

    but yesterday I drove my car in 20 degree temp in HUGE gusting winds at 60 mph, but the car was preheated and the battery was warm (no "yellow dash" on the regen screen)
    I was pulling about 350 to 375 Wh/mile

    today at the same temperature, with no wind, but with ice cold battery I was driving 60 mph...
    my car was pulling 520 Wh/mile.
    when I turned the heat on (seat heater and steering wheel not enough), it went up to 730 Wh/mile!

    after a few minutes, it fell to 450 Wh/mile

    I'm assuming this shows the battery heating cost, and the cabin heating cost.
    there were no other changes. (empty highway at 60mph)
     
  15. Doubletap67

    Doubletap67 Member

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    Certainly sounds like the expected and logical behavior, and what I saw last night. Maybe I don't have enough experience yet to figure out when the usage is hidden, and when it's expressed in mileage consumption. Pure distance times energy/distance gives me wildly variable energy per battery percentage drop.

    And helped a lot, thank you.
     
  16. JRMW

    JRMW Member

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    you're welcome.
    on a side note, I see you're Canadian.

    My 20 degrees was Fahrenheit.
    that would be about minus 6.7 degrees C.

    I have to say, it is sad that I'm only getting about 120 to 130 miles per charge.
    then again, I rarely drive more than 30-40 miles in a day so it doesn't matter.
    (at least it won't once my electrical company hooks up my darn service!)
     
  17. Doubletap67

    Doubletap67 Member

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    Do you also have a new 60? I'm probably getting about 150 miles from my short little drives so far, but you're in a lot colder conditions. I may do a 100 mile drive to a supercharger just to see what happens to my range.
     
  18. Doubletap67

    Doubletap67 Member

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    I'm getting 12 kW from my wall connector so the capacity is almost meaningless. I recharge a regular day of work and driving around afterwards in two hours or less. I had to upgrade my service to 200 amps but the convenience has made it worth it. Obsession with discharge behaviour is in preparation for the occasional road trips we take (and more than a little bit of OCD about getting as much capacity as I paid for).
     
  19. jerry33

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

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    What appears to happen, at least as far as I can tell on my car is: If you are charging and preheating, the rate of charging goes down. If you are not charging and just preheating, and you get into the car, turn off the cabin heat, and then wait for the green blinking to stop, it takes about twenty seconds while replenishment charging continues. I can't tell how much is going to the battery heater vs. the cabin heater, but I can see the difference in the regen line. I think the trick here is "full power", the heaters likely don't always run at full power (or they cycle on and off to emulate partial power).
     
  20. JRMW

    JRMW Member

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    Yes 60D.

    Part of the problem is that my car will not charge using my regular outlet in my garage.
    the first day it worked. it pulled about 4 miles/hour. it was awesome. I woke up the next day with a full battery, and my real range was probably about 150-160 miles per charge.

    since the first day, however, I can't get my car to charge using the trickle charger.

    the car will start to charge and within a few minutes it says "charging interrupted"
    I've tried everything, but the charging always interrupts within seconds.
    then my car becomes cold soaked through the night
    and I lose a lot of range heating the battery the next morning
    then my car gets cold soaked all day
    then I use a lot of range heating the battery after work.

    so as example:
    yesterday I charged at supercharger. had 215 miles of range and a warm cabin and warm battery.
    20 degrees (minus 6.7C) but a lot of wind.
    drove 19.9 miles.
    but my car said I had 187 miles of charge remaining. (so I used 28 miles of charge to go 20 miles)
    hooked car up to my trickle charger. immediately got interrupted
    woke up this morning and I think I had like 180 miles. (so lost 7 miles while "parked" overnight)
    drove 14.2 miles. charge went down to 159 miles. (so used 21 miles of charge to go 14.2 miles)

    so looks like I use aobut 3 miles of charge to drive 2 miles.
    215/3*2=143

    My guess is that I'll get FAR better range once Xcel energy hooks up the 200 Amp service in the garage.
    (it's all been done for 2 weeks, and simply waiting for Xcel energy to hook it up... the utility pole is probably 10 feet away. argh!)
    because then I can start each day with a toasty warm car with a warm battery!
     
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