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Max Battery Power to Preheat Cold-Soaked Traction Pack? Possible? Pros? Cons?

Discussion in 'Model S: Battery & Charging' started by Andyw2100, Oct 19, 2015.

  1. Andyw2100

    Andyw2100 Well-Known Member

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    #1 Andyw2100, Oct 19, 2015
    Last edited: Oct 19, 2015
    Until Tesla gives us a true traction pack pre-heating option, I'm wondering if it may be possible to use the new Max Battery Power mode to pre-heat a cold soaked traction pack from shore power to the point where there would be no regen limit, but then stop the heating before it got to the point where any degradation could occur.

    I think there are many questions that need to be answered.

    The first is whether or not Max Battery Power even uses shore power to heat the pack, or if it is set up to only use power from the pack, since it is intended to be used while driving. Can Max Battery Power be on and heating the pack while the car is off? Another question is does Max Battery Power somehow heat the pack faster and in a less healthy way than the way it is heated when it has to be charged, for example.

    Assuming it is possible and safe to begin heating the pack this way, another question is how to know when to stop the heating? Also since this option is not available, at least for now, through the API, in order to heat your pack using this mode you'd have to physically go to your car.

    If it's not possible to use Max Battery Power while on shore power, and/or while the car is off, is it possible to use it with Range Mode on? Why would we want to do that? Well, many of us with Ds keep Range Mode on because we want to maximize the benefits of torque sleep. But with Range Mode on, the pack won't be heated separately at all as we drive, so any regen limits are quite slow to disappear. We may be willing to use some power in order to get rid of the regen limits, while still wanting to maximize the benefits of torque sleep. A brief period of time driving with Max Battery Power mode on might accomplish this.

    There's no question that a more dedicated traction pack pre-heating mode would be simpler, and I have a couple of old threads going on that (see below), but in the meantime, I'm wondering what people think about the above.

    Suggestion for battery pre-heating and charge-end scheduling sent to Tesla

    Would you use battery heating if it were available?
     
  2. ArtInCT

    ArtInCT Always Learning

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    This is a very good question Andyw2100. What we all need to know, is that if MAX BATTERY POWER is invoked, and the car is on shore power, will the car use the shore power to do the conditioning.
    For instance in the winter in a cold garage.

    Also, do any of the APPs allow you to invoke MAX BATTERY POWER via a remote setting at this time or in the future? It will be inconvienient to have to go to the car to physically turn this on for many folks.
     
  3. AWDtsla

    AWDtsla Active Member

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    Yes it uses shore power, 5kW. If you happen turn on cabin preheat as well, your charge rate can become negative, I got it to go 2kW _draw_ from the battery and still 40 amps from the outlet while trying to charge. If you're going to start warming it and turn up the charge limit in order to go hooning around on a cold day, you're going to have to wait a long long time if you don't have a HPWC and dual chargers (I assume all shore power goes through the charger)

    With the pack probably around ~55F the estimate was 50 minutes at what seemed to be a constant 5kW draw. That's _a lot_ of heat.. Unlike people who tested before I am seeing a steady increase in max power while waiting for that 50 minutes to be up, 422kw, 428kw, 434kw (~80% SOC), and then I shut it off with another 15 minutes left on the clock since I was done driving. If I were to do it all the time my fueling costs would pretty much equal my gas car.
     
  4. StaceyS

    StaceyS Member

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    What I've done is turn on the cabin heater and raise the charge level. This causes the heaters to draw power from the battery, and the chargers to draw power from the grid. The car wants the battery at a specific temp for charging, so it will heat the battery as well. Doing this has been a fairly reliable way to get into a warm car with no cold weather related regen limits.

    I've got a P85, so the "Max Battery Power" option isn't available to me.
     
  5. Andyw2100

    Andyw2100 Well-Known Member

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    Thanks, StaceyS.

    Many of us are pretty well-versed in the "traditional" ways to heat the pack. The problems with what you suggest that I had hoped might be eliminated through the use of the Max Battery Power option, and that would definitely be eliminated if Tesla simply provided a battery preheating option are that we are wasting energy heating the cabin when its not necessarily the cabin that we're trying to heat. Also in order to raise the charge level of the battery and start charging it would require having charged the battery to a lower level previously, which brings another set of problems: charging at possibly higher rates, possibly not having enough time to complete the charge, etc.

    Based on what I've read in other threads about what people think the Max Battery Power option may be doing, I'm not going to utilize it just to raise the pack temperature in an attempt to not have regenerative braking limits. I'll keep waiting--perhaps indefinitely--for Tesla to provide a dedicated battery preheating option.
     

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