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How cold is cold ?

Discussion in 'The UK and Ireland' started by mnobleuk, Sep 27, 2019.

  1. mnobleuk

    mnobleuk Member

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    Got the snowflake icon and blue battery this morning.

    The car said it was 12 degrees C which doesn't strike me as particularly cold.

    The manual is very non specific just citing "cold weather".

    Is anyone else getting this already - seems like in a few months time that's it will be permanently on !
     
  2. LEE3

    LEE3 Member

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    I was wondering this also. Not had any signs from the car as yet. Also as an associated question, If you go about preheating the battery sufficiently before setting off, does the car typically then remain warm with regen available until you reach your destination?
     
  3. Andy_T_73

    Andy_T_73 Member

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    I don't think you can pre-heat the battery on an M3, AFAIK it uses heat from the motor to warm the battery in cold weather.

    Anyways, link here to some useful cold weather EV tips
     
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  4. cezdoc

    cezdoc Member

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    I've never seen the blue battery/snowflake on my Model S (have had it through a couple of Aberdonian winters). I'd always assumed it was something you were only likely to see in winter continental, minus double-digit, conditions.
    12 C is the sort of temperature where you start to notice the regen being limited a bit when starting off cold - but that just shows up as dashed yellow lines on the power meter and a small warning triangle icon.

    Yes, the heat generated just by discharging the battery and then recharging under regen seems to do more than the battery pre-heater; also I believe the car recovers some heat generated by the motor(s) and drive train. When starting from cold straight into slow moving traffic I have the impression that the car runs a heater until the yellow dashed lines cover about half the power meter; after that the power drain drops off so I speculate the rest is done by scavenging heat as the car is driven.

    FWIW if you're able to, I think it's more efficient to pre-heat the battery by scheduling a charge to finish just before you set off, rather than getting the car to run its heater.

    I guess in both cases the Model 3 might behave differently since the battery cells are different to the S/X.
     
  5. arg

    arg Supporting Member

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    I believe the temperature at which regen starts to be limited is around 10C (at least for Model S). Note that it's the battery temperature that matters, and the battery has large thermal mass, so if the battery has soaked down to a low temperature overnight it may be much colder than the air temperature when you start to drive away. The temperature for optimum efficiency is much higher than this, so in winter driving it can take a very long time to get there - typically the 2nd half of a long trip will show better efficiency than the 1st half even if you think you've been cruising at uniform speed.

    OTOH, the temperature for regen to be totally disabled is much lower (around zero I think, though less sure about that) and it relatively quickly gets warm enough to allow some regen - primarily because it runs the battery heater in those conditions.

    In UK weather, it's very unusual for things to get worse while you are driving. However, it's hard to preheat sufficiently to completely remove the regen limit, and if you drive off with (say) half the normal regen it can take a very long time to get to full regen if you are driving in city traffic - under those conditions it doesn't run the battery heater, so you are relying on motor waste heat and self-heating as current is drawn from the battery, both of which have minimal effect if you are just crawling along in traffic. Bombing down the motorway will remove the regen limit relatively quickly.

    The answer to "why don't they make it easier to preheat to get rid of the regen limit?" is that there's no point - for a short trip the energy wasted in pre-heating would be vastly more than would have been regained by the extra regen, and for a long trip the waste heat will get you there soon enough for free. So the only real reason for wanting to do that much preheating is if you don't like the driving experience with partial regen.

    I don't think this is relevant. Both Model S/X and Model 3 use waste heat from the motor to heat the battery; Model S/X also have a separate battery heater (at least in classic versions), while Model 3 runs the motor in a deliberately inefficient mode to achieve the same effect.

    You couldn't have no active battery heating mechanism at all, since you need to be able to charge in sub-zero conditions (where you can't charge at all without heating the battery). There's also no reason to believe the 3's motor-as-heater mechanism is less powerful or efficient - the amount of waste heat coming out of the motor at full bore is greater than the rating of the Model S separate heater so the liquid path has to be up to the job, and there's no difficulty running a motor of that type at 0% motor efficiency (= 100% heater efficiency) so the electrical path is better.

    So while Model 3 is different in how the scheme is implemented, the net effect is the same.

    I wouldn't be surprised if the Raven Model S has ditched the discrete battery heater in favour of the Model 3 scheme (given it has the Model 3 motor), but I haven't seen this reported one way or the other.
     
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  6. ewoodrick

    ewoodrick Well-Known Member

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    I believe that was just indicating some limited regen. No problems, just a notification.
     
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  7. Silicon Desert

    Silicon Desert Active Member

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    What kind of car are we talking about in the OP posting? Just curious. In 3 winters up here in Reno (many days and nights of 10-20 degrees F), I have never seen the snowflake or blue battery thing that is being mentioned. Model X 2016 here.
     
  8. mnobleuk

    mnobleuk Member

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    Model 3 SR+ I’m now wondering if there’s an issue with the temperature sensor ?
     
  9. M3BlueGeorgia

    M3BlueGeorgia Active Member

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    Perhaps, but the car is super-protective of the batteries in cool and cold ambient temperatures.
     
  10. VanillaAir_UK

    VanillaAir_UK Moderator UK and Ireland

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    12C isn't what most people would call cool or cold although I might not be out in a T shirt as I'm not from Warrington.
     
  11. Adopado

    Adopado Active Member

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    My Model 3 definitely has its regenerative braking affected at higher temperatures than that. It seems to be on a continuos sliding scale. The number of regen dots (it took me a couple of weeks to even spot them) are higher on cooler days. Once you start paying attention to it the indicators are there even at temperatures of 15 or 16 degrees C. It's not like there is a single temperature that makes a sudden change, it's progressive.
     
  12. arg

    arg Supporting Member

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    If the temperature was reported on the dash/app as 12 and all that happened was a slight reduction in regen power, then all is good- probably the pack was a couple of degrees below ambient having cold soaked overnight.

    If something more extreme was happening (like no regen at all) then that would be suspicious.
     
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  13. WannabeOwner

    WannabeOwner Well-Known Member

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    Car (battery) will warm up as you drive, so unless all your journeys are very short then it won't be "permanently on" :)

    But, yeah, I have some reduced Regen early in the morning on some days at this time of the year.

    There isn't really an option to pre-heat the battery per se. Charging it before setting off helps, but even in cold weather the battery heater doesn't stay on during charging. Normal driving will warm the battery further, and keep it warm so, e.g. a long winter journey will have modest loss overall, whereas travelling-salesman, stop for an hour multiple times, will have the full cold-battery-set-off-penalty each time. That's worst case for an EV owner.
     
  14. Hugh Mannity

    Hugh Mannity Mediocre Member

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    In my Model S the snowflake doesn’t come on till it’s below -20C, I don’t know what that is in Fahrenheit, 5 to 10? Something like that.
     
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  15. tess19

    tess19 Member

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    Can i ask why one would want to waste energy to preheat the battery in order to enable regen? Isn't that a bit of a oxymoron?
     
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  16. Hugh Mannity

    Hugh Mannity Mediocre Member

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    two things:

    1. best scenario is do it when plugged in, the pack heats via shore power

    2. It’s still a good idea to warm the pack if it’s not plugged in, then you get regen and better performance. No regen is strange! Too much friction brake
     
  17. tess19

    tess19 Member

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    But using mains electricity is not very eco ;)
    Also might as well use the upgraded brakes in my M3P+ . Dont get chance to use it otherwise.:D
     
  18. Rooster6655

    Rooster6655 Active Member

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    Limited regen is just annoying as the car doesn’t slow down as it normally would, thankfully it’s not always for that long.
     
  19. VanillaAir_UK

    VanillaAir_UK Moderator UK and Ireland

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    I must admit, I thought driving on next to no regen would be odd. But its not too bad and unless you are driving on the edge, plenty of warning and opportunity to cover any shortfall with the brakes, even on a relatively steep downhill coming to a full stop - at least my experience with driving on hold.
     
  20. LukeT

    LukeT Member

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    It's a fair point. It uses extra energy. It's not an exercise in reducing energy used.

    That bit of pre-heating is spending on shore power to extend range, essentially. Might be worth doing before a range challenging journey to prevent a charging stop, so for convenience. I sometimes charge late and add a bit of HVAC for this reason - my regular journey is one that in winter is running me fairly close on range.

    Alternatively it's spending on shore power to maintain the same feel of driving the car, which is pretty frivolous. I admit though, I do see the advantage if I'm pre-heating anyway for the reason above.

    It might also be worth noting that this bit of extra, unnecessary, energy use is probably quite often put in at times of higher carbon intensity of the grid (essentially any time other than 11pm-7am). This isn't very good.
     
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