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Lack of battery heater may cause very slow SuC charging speed

Discussion in 'Model 3' started by EvanLin, Jan 8, 2018.

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  1. David99

    David99 Active Member

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    Based on my experience, absolutely. The coolant goes through the entire module which is pretty long on the M3. You definitely do not want to create too much of a temperature difference between the cells. Equal temperature cross the entire battery is just as important as the temperature itself. For almost 2 years now I have looked at the CAN bus data in realtime checking the battery temperatures for each module and how much it differs going in and going out on my Model S. The highest temperature difference between coolant going in and coming out is maybe 4 degrees C. The motor and inverter can be 80 C or more but the coolant going into the battery is never much different from the cell temperature. So I'm convinced that's by design.

    Just a real world data point that relates to your calculations. I did a test heating up my battery from about -9 C to 12 C and it took about 35 min and used aprox 3 kWh.
     
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  2. Zythryn

    Zythryn M3 Silver, M3 Midnight Silver

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    You guess is a logical one, I would just like to see more information.
    Timing of the battery heater kicking in would also be valuable information to have. Unfortunately I don't know the temp the S battery pack kicks in.
     
  3. Big Earl

    Big Earl bnkwupt

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    I'm pretty sure @David99 knows more details, but I think the battery heater won't kick in until something like -13F without user input (preheating via app, charging, etc.). At 0F, the car wouldn't have run its battery heater while parked overnight unless it started charging, automatic preconditioning, or you asked it to with a preheating command.
     
  4. AWDtsla

    AWDtsla Active Member

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    -13F? LOL no. IIRC it used to be 8C (46F) with range mode off, while in drive, charging, or preheating.
     
  5. Big Earl

    Big Earl bnkwupt

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    Yes, but this particular discussion is about sitting unused overnight, not charging, preheating or while in drive.

    @kalikgod showed an app screenshot of his Model S and Model 3 after cold soaking overnight and attributed the slightly warmer interior temperature of the Model S to its battery heater, which I don't believe would have been running while parked overnight.
     
  6. David99

    David99 Active Member

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    The Model S/X definitely do not turn on the battery heater just on it's own being parked. Even when plugged in. It only does so when you start charging, get in the car and thus turn it on, or heat the cabin via app.
    I don't have a Model 3 to test, but I'm confident it works the same. Anything else would be a huge waste of energy.
     
  7. kalikgod

    kalikgod Member

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    They were @outdoors pictures, not mine. I suggested he take them down because of some personal info that could be seen in them.

    Maybe he could crop the photos and post again.
     
  8. outdoors

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    There was no sun at the time. Going to post some others as well. Cars had not been operated and no climate control. Even had both of us turn off Bluetooth and kept key fobs away. 20180117_163717.png 20180117_163649.png
     
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  9. outdoors

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    Brought car in from being outside all night again to charge. 1 and half days. Here is my experience. Needed to pull into garage to get to charger. Garage approximately 40 degrees once closed. Doubt that once opened it was that. Time stamps etc should help . IMG953720.jpg 20180116_145906.jpg Screenshot_20180116-150317.png Screenshot_20180116-151743.png Screenshot_20180116-154126.png Screenshot_20180116-154428.png Screenshot_20180116-155548.png
     
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  10. kalikgod

    kalikgod Member

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    Thanks for reposting and the additional info!
     
  11. AWDtsla

    AWDtsla Active Member

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    Points to the available heater capacity for the pack being less than 2.5kW (10A*246V). Not good Tesla, not good.
     
  12. scaesare

    scaesare Well-Known Member

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    Looks like ~40 mins to get the battery up to temp for full charging.

    I don't know that I've ever started a charge with my car that cold, although I've driven it at those temps.

    How long would it take a Model S that's been cold-soaked to ~16 degrees to do the same?
     
  13. outdoors

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    Will roll out the S tonight. Let it cold soak to low of 14 tonight. All day tomorrow high of 29. Then will bring it back in at 8pm should be about 22. Current SOC is 38%. Little off topic, but comparison of the two brings it back to bar stool.
     
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  14. David99

    David99 Active Member

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    Without know the actual battery pack temperature this is all very speculative and guesswork. Ambient temperature doesn't say too much about battery temperature.
     
  15. Big Earl

    Big Earl bnkwupt

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    Ah, very good. When I couldn’t find them again, I made the mistake of thinking they were yours.
     
  16. LectrikPower

    LectrikPower Member

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    I'm thinking about putting a small heater on the garage floor in front of the car, on a timer, to keep the pack warm in the winter. Thoughts?

    It seems like that may be good for pack longevity and initial performance ie no restricted regen.
     
  17. mongo

    mongo Well-Known Member

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    A waterproof radiant panel located under the pack may help due to better coupling.
     
  18. Dax279

    Dax279 Member

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    Here is an interesting find. The tempurature limits description in the owners manual reads differently for the model 3 than it does for the S. For the 3 it states to not expose the car to temperatures below minus 30 C for more than 24 hours. For the MS the description reads don’t leave the car unplugged at these temperatures for more than 24 hours.

    They do say that this is for better long term performance in the M3 manual.
     
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  19. ChooseGreen

    ChooseGreen Member

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    Help a non-electrical engineer here.

    I keep thinking of applying power to a motor, but not allowing it to turn electrically or physically, and it brings burned out motors to mind. Is someone able to explain how using the inverter and motor as a resistive heat source isn't damaging to the motor and inverter electronics and wiring?

    I'm guessing that the idea is that the cooling lines will bring away any heat and therefore not allow it to reach damaging temperatures, but I keep thinking about an area of copper coil which is away from a cooling line heating up to the point of damaging itself.

    Thanks for any good explanations and/or soothing words that this is a good idea for heating :)
     
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  20. mongo

    mongo Well-Known Member

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    Normally, a motor is converting electrical energy to mechanical as efficiently as possible, so it doesn't heat up much. Torque is usually related to current, current causes heating in the motor windings due to resistance, P=I^2*R. So the motor is built so that the heat generated during operation can be removed such that the max temp of the windings/ bearings is not exceeded. This is the limit to how much heat you can reliably get from the motor.
    To generate heat instead of motion, the inverter sends a stationary field instead of a rotating one (or if the car is moving, both an additional acceleration and deceleration field). But since the motor is not spinning, there is no back-EMF voltage to counteract the inverter drive, so the inverter needs to be able to throttle way back in terms of total power and pulse width to the motor.
    AC motors also generate heat in the rotor due to the induced (hence inductive AC motor) field, DC motors are primarily generating heat in the windings.

    So its basically like stalling a motor, but with a low enough power level that it doesn't burn up. If the motor is normally 95% efficient, you can only get 5% of power capability out of it in the form of heat. (less if the motor runs it's own cooling pump)

    Hope that helped.
     
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