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Max power vs temperature vs charge

Discussion in 'Roadster' started by Alan, Nov 28, 2013.

  1. Alan

    Alan Member

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    Hi,

    Around this time of year I notice a real drop off in the performance of my Roadster and was wondering if others have seen the same.

    I am in the UK and the temperature most mornings is between 2C and 8C (36F to 46F).

    I tend to charge at work in range mode, then drive home about 25 miles so the car shows say 130 miles ideal range. Most days the car lives outside not plugged in.

    Next morning the car is down on power and feels sluggish, the outside temp may be a bit low but looking at the logs the battery temp is usually around 15C rising to about 20C during my drive to work. The dashboard dial will go up to about 150kW and however hard I try I can not get the display on peak hold to go over 200 BHP. The battery temperature bar graph usually shows the temperature 1 box above the minimum. Running the car in performance mode does not make any difference.

    On the way home with the battery fully charged in range mode the battery temp starts at about 20C and rises to say 24C on the 24 mile drive home. Exterior temp still about 10C. I can now get about 230 BHP (accelerating up a long hill) and the car feels more lively but that is still some way off the quoted 288 BHP.

    Does anyone else have the same? It seems to me as if max power available depends on exterior temperature as much as battery temperature.

    Thanks
    Alan
     
  2. pharma5

    pharma5 Roadster F#25

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    Have not experienced this issue (less power at lower ambient temp). Although mine sleeps indoors, I don't see it after sitting at work for 8+ hours when temp is near freezing.

    Is it possible you are driving in Range mode? That is supposed to limit power a bit.
     
  3. Alan

    Alan Member

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    Not in range mode (but it feels a bit like its in range mode), the power seems limited in both normal and performance mode.
     
  4. djp

    djp Roadster 2.0 VIN939

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    I notice my performance goes off a cliff in the winter as well. It happens the day I put my snow tires on. :smile:
     
  5. Doug_G

    Doug_G Lead Moderator

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    I've not seen the power back down. Regen goes away, for sure. But power delivery is limited by the cold temperatures affecting the tire's grip on the road. So when it's extremely cold I've been unable to punch it and maintain traction.

    Is the TC light illuminating? Maybe the tires are slipping when you punch it, and the TC is backing off the power.
     
  6. Alan

    Alan Member

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    No traction control light when I floor it (unless road wet / bumpy etc) / still have regen as battery not that cold - not even on bottom step of the bargraph.
     
  7. wiztecy

    wiztecy Active Member

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    #7 wiztecy, Nov 28, 2013
    Last edited: Nov 28, 2013
    Battery current/flow is directly correlated to temp. Just like how you heat your pack up in performance mode you get the most performance/flow/current out of the pack so the inverse is also true. The colder the pack the higher the resistance is and less current flow of energy occurs. Also you will have reduced range and a small drop in CAC in colder temps.

    My single 12v lead acid battery in the camper doesn't last all that long in cold weather, below 50 degrees F. And when its below 30 good luck!

    "Li-ion also performs better at high temperatures than at low ones."

    From the battery wiki below.

    This should help you understand battery current and discharge rates with temp:

    Discharging at High and Low Temperatures Battery University

    So to conclude, nothing is wrong with your Roadster :)
     
  8. dhrivnak

    dhrivnak Active Member

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    Alan if you are charging in range mode most days then unless you reset when you drive your power will be limited to 1/2 power. Charging in range mode also puts you in reduced power mode by default. Also from that I hear from members and Tesla range mode should be used only on occasion. Daily use will negatively impact your battery.
     
  9. Alan

    Alan Member

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    Doh - I never charge in range mode. I mean standard mode. I drive always in standard or performance mode.

    - - - Updated - - -


    Perhaps, but it would be good to hear from someone else who has the same symptoms. If anyone can leave their car off charge overnight with an outside temp of between 2C and 8C (36F to 46F) it would be great to know if you can get > 200 BHP with a battery > 1/2 charged.
     
  10. djp

    djp Roadster 2.0 VIN939

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    I notice my car is more zippy at full charge compared to half charge, so I'm not surprised you can feel a temperature effect as well. Max horsepower is reached by charging in Performance mode, which targets a higher pack temperature than Range mode.
     
  11. wiztecy

    wiztecy Active Member

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    #11 wiztecy, Nov 28, 2013
    Last edited: Nov 28, 2013
    I don't understand the problem here. If you feel reduced power every winter where temps drop and your holding all other variables constant, wouldn't you think that that one variable that's changing has a direct correlation on any effects in change between the two comparative figures? You also are starting in cold with a battery that's 1/2 depleted. A half depleted battery will not provide the same power as a full pack, that coupled with cold weather will have some major effects.

    I leave my Roadster out at night, temps drop down to 43F, I charge and allow it to sit, but I know that any reduced power is an expected behavior with the cold. Yes I do feel reduced power as compared to 70-85F temps.

    Its like saying your ICE engine does not perform as soon as your start it up in 20F degree weather and immediately stomp on it versus when you start it up drive it in the summer with 80-90F degrees and stomp on it directly after startup. (however with ICE there's an upper limit where the combustion is not ideal and power begins to drop as more heat is added. i.e: overheating and typically above 208F in cooling temps. A wood furnace is a better comparison, it runs even better and hotter as more heat and hot air is introduced into the combustion chamber.)

    Its physics and chemistry, its a fact that molecules move slower in cold. Heck even I do until I get warmed up!
     
  12. dhrivnak

    dhrivnak Active Member

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    I think I was able to replicate your situation as it was 20F this morning. While my garage was about 48F I went out for a few hours. Initially when I floored it I would get 280 ft-lbs of torque. But after the battery got good and cold the maximum torque dropped to about 225. I never noticed before as I never tried to hot rod it in the cold. Later int he day when it got up to 50 I tried again and got 280 ft-lbs, which is about the max I have seen in the car. I even see this full power with 1/3 battery as I spent a long day at the track this past summer. So I do not think it is the half charge that is slowing you down at all. But it looks like a cold battery will slow things down.

    As others have noted a cold ICE engine will see even more of a power drop so it is not unique to Roadsters.
     
  13. jeremyz

    jeremyz Member

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    That's not true of all ICE engines. Turbo-charged engines love cold weather. It's like somebody upgraded your intercooler with a giant one while you slept.
     

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