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How long can you run accessories/heating with Zero Range?

Discussion in 'Model S: Battery & Charging' started by tom66, Jan 20, 2014.

  1. tom66

    tom66 Member

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    I was talking to a "petrolhead" friend of mine about the Mdel S, and one question he asked me that I couldn't answer was that in the instance that you do truly run to zero range, and past the "charge now" point to a completely dead battery (car is immobile), do the cabin controls still work for heating? And for how long? I made the point that they wouldn't work in an ICE either, with no fuel, as heating is bled off the engine, but he contended that you'd have at least reasonable heating for some time as coolant circulated through the still warm engine block (and the fan and coolant pump would run off the 12V system in most cars.) I don't know how long this would be on most cars - they are designed to lose heat quickly after all - maybe 15 minutes?

    While it's not that relevant in the UK, it could be pretty important if you get stuck in the middle of nowhere and don't have heat and it's -10°C outside...

    Anyone have any experience/data?

    Thanks
     
  2. qwk

    qwk Model S P2681

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    Most ICE vehicles have a belt driven water pump, and since you need to circulate the hot water through the heater core to get any heat out of it, the heater will not blow warm air for more than a few seconds after the engine is shut off.
     
  3. tom66

    tom66 Member

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    I didn't know that. I'll mention that when we next talk. I thought most of them were electrically pumped; I'm an electronics engineer, not a car mechanic.
     
  4. Canuck

    Canuck Active Member

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    If you get stuck in the middle of nowhere with no heat and no range, it's not much different than having ventured out there with no gas remaining. When my ICE vehicle is not running, the fan goes cold after about 5 minutes at most and that's after the engine has been running for some time before shutting it off. Given the scenario your "petrohead" friend presented, I would have replied that the low IQ of the person venturing out into the middle of nowhere with low range/gas should be the real concern.
     
  5. jerry33

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

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    My experience has been that ICE car heaters blow cold air in under a minute if the engine is off. This is because the coolant no longer flows so only the heater core has to cool off--and it cools off very quickly. If the car has an electric coolant pump and the pump could be made to run (most run thermostatically controlled and wouldn't run in this situation), then you might have ten or fifteen minutes. But you'd have to install an override switch. I don't know of anyone who has done so.

    In practice you're much less likely to run out of energy in an electric car than fuel in an ICE car. The main reason is that with an electric car you plan your charging stops while in an ICE car you play it by ear.

    Regardless of car, the correct thing to do is keep a few candles in the car and a couple of space blankets. These will keep the car and you warm enough so that you don't freeze. This technique works quite well in -40 weather.
     
  6. Lloyd

    Lloyd Active Member

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    I think I can sort of answer that. In the two cars I have had once you get close to 0, you get Charge Now. About two miles past that, you get a warning that the heat/AC is running on decreased output to preserve remaining battery. I did not answer the question specifically, but I have driven another 3 miles and the car did not shut off or systems inoperative. Others have said the cars will shut off about 5 miles past zero. So once at Zero I would say you have at least 1/2 hour of minimal heat, depending on how much the inside to outside differential is. This is an estimate only. Don't try this at home children!!!
     
  7. jerry33

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

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    If you just ran the seat heater(s) you'd have much longer, and assuming you have a blanket, you'd be good for a long time.
     
  8. tom66

    tom66 Member

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    Does anyone know if the seat heaters operate off the 12V or HV system? If they operate off 12V there would be additional battery capacity available...
    I know a lot of (all?) ICE cars use 12V for seat heating. It's very expensive to route coolant and do it any other way.
     
  9. jerry33

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

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    They would run off the 12V system. As far as I know they are just standard seat heaters.
     
  10. Forty Creek

    Forty Creek Member

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    ...however the seat heaters will not turn on unless the car is on. I.E. you can't turn them on from the app. If the SOC is so low that the car won't run, I suspect seat heaters might not turn on either.
     
  11. jerry33

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

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    They might not, but if the car stops I'm not sure that it actually shuts off. If it doesn't shut off, then you could use them. Probably we won't really know until someone tries and posts the result.
     
  12. yobigd20

    yobigd20 Well-Known Member

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    It depends what electronics you are running. If running heat/AC, it wouldn't last very long. The heat pump alone uses around ~6.5kWh. One of my 'lets see how inefficient I can be' days driving home, I arrived home with about 3 miles rated range left. I just sat in my garage parked and I turned heat on high MAX non-range mode. The kWh bar seems to hover around 6-7kWh and I watched my range drop from 3 to 2 to 1 to 0. This only took a few minutes. I'd say maybe 7 or 8 minutes max. I just wanted to get it down to 0 for once just so I could say I did it. It did get pretty hot in there...had to start stripping off some of my winter gear, lol.
     

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