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Noob Question... Warming Battery?

Discussion in 'Model S: Battery & Charging' started by sandpiper, Jan 6, 2015.

  1. sandpiper

    sandpiper Active Member

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    Question about the Tesla App.

    In cold weather, how do you tell the car to warm up the battery while it's still attached to the charger - so as to avoid losing the extra power once it's disconnected?

    Does it happen when you turn "climate" on?
     
  2. DCWitt

    DCWitt Member

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    Sure does.
     
  3. ChrisPDX

    ChrisPDX Member

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    Pre-heating the cabin is really the best way to go. The cabin heater also uses a lot of energy at first. So by pre-heating while plugged in, you shift a lot of power use to wall power. It will also start pre-heating the battery as well.

    Another method is to charge to about 10% less then normal, and then restart the charging process before you leave. This will also kick in the battery heater. I'm hoping one day Tesla will change the charging scheduler to allow you to specify an end time, not just a start time. That way it will just finish charging and fully warm the battery when you leave.

    Finally, the last method is to enable range mode. What this does is it stops the battery heater once it gets the battery warm enough to limit the regen to about 30kW. After that, it only uses the motor/inverter heat to warm the battery. So in very cold climates, it keeps it from running as long and in slightly warmer climate it will keep it from running at all (at the expense of limiting your regen).
     
  4. jgs

    jgs Member

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    Interesting, this seems to suggest that regen in the 30-60kW range contributes less to range on average, than the energy cost to maintain the pack in the necessary temperature range. In that case, why does the car EVER do so? I can imagine at least three answers -- that the pack is also not capable of delivering peak output when not kept warm, so acceleration is power-limited, that range mode is only optimizing for the highway cruising use case where hard deceleration is not often needed, but in other cases such as city driving 30-60kW regen would be worth the joules to keep the battery warm, and finally maybe it's considered valuable from a user experience point of view to maintain consistent regen feel when possible, even if it's at the expense of efficiency. But this is all guessing -- can anyone speak more authoritatively about the reason?
     
  5. scaesare

    scaesare Active Member

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    I actually have found that battery charging warms the battery faster than the cabin heater. It has the advantage of not turning off after the cabin reaches temp and/or the timeout period (15 or 30 mins ,depending on FW version).
     
  6. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    And better yet, do both; charge the battery and pre-heat the cabin!
     
  7. scaesare

    scaesare Active Member

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    For the last few minutes, sure... primarly for occupant comfort.

    But if the goal is to warm the battery, then the several kW of power that the cabin heating can draw is energy not being put in to the battery.
     
  8. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Sure, but when I am in this situation, I want to store as much energy in the car as possible before a long distance winter drive, and I am at home without a time constraint. Given those conditions, I want as much charge in the battery as it will hold, the battery warm, and the cabin warm before I leave. Charging the battery, and preheating battery and cabin, all store energy in the car. Given that it takes an hour or more to heat the battery, and a half hour or so to heat soak the cabin, I turn on everything early and long before dashing out into the winter wonderland.
     
  9. jerry33

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

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    Generally you do the preheating just as the charging is ended--or just after. Since you're not putting any more energy into the battery there's no problem. Preheating the car often means you don't even need to run the cabin heater, or if you do, it's at a much lower level.
     

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