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Battery heater not working?

Discussion in 'Gen 5 Prius Technical Discussion' started by KMO, Jan 6, 2024.

  1. KMO

    KMO Senior Member

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    Yeah, I've seen discussions about how much regenerative braking is or isn't limited when cold, and the concensus seems to be towards "it's not limited much, if at all".

    I'm wondering if the thing there is time - maybe they're not worried about a 5-10 second high-current pulse in the same way they'd be worried the same current maintained. You possibly can't simply apply discussions of safe charging currents (ie for many minutes or a few hours) to a regeneration pulse.

    Proper investigation would need someone to launch themselves down a hill well below freezing. My current guess is that it will stop regeneration after a short-ish time in a way that it wouldn't when warm.
     
  2. KMO

    KMO Senior Member

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    Morning figures had the ambient temperature at -13°C - it would have been maybe up to -8°C during the night. Battery temperature had risen from -16°C the evening before to a spread from -5°C to -1°C, showing that it must have finally decided it was worth applying some heating. The temperature spread was presumably an artifact of uneven heating. All the temperatures seen previously were all within a one-degree band.

    So a first-guess estimate is that the battery heater goes into operation with ambient and battery temperature both above some temperature in the -15°C to -10°C region, and below that it won't bother.
     
    #22 KMO, Jan 8, 2024
    Last edited: Jan 8, 2024
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  3. vvillovv

    vvillovv Senior Member

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    In the Gen 4 Charge Settings on the MID there is also an option to reduce the in car chargers output to 8 Amps instead of the Default Max. At the 8 Amp setting it takes the Gen 4 around twice as long to charge as it takes for the default max setting.
    The lower (trickle ? ) setting could be helpful for manual control of charge speed when charging during very hot, very cold and ( very high traction pack internal resistance, like can also be seen in DrPrius app ).

    I think it would be wise to wait until we see if that is also true with the battery heater turned on in charge settings. Although I agree it really good to know how the car behaves with the heater function turned off, too.
     
    #23 vvillovv, Jan 8, 2024
    Last edited: Jan 8, 2024
  4. KMO

    KMO Senior Member

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    That still exists in G5, but you shouldn't need to use it to protect the car, as the car's already chock full of temperature/SoC determination of charging current. That's there just if you need it to avoid blowing your household fuses.

    I think you maybe misread something there? I'm only testing with the battery heater enabled in settings, and that's what I'm talking about.

    Evening report - car was parked outside today at -9°C or so without the charger connected, and managed its first EV operation for over a week on the way home. (Still started the engine initially though). Checked battery temperature after arrival, and the batteries were at -9°C.

    And when plugged in at home, it did start the battery heaters (which warmed up to around +30°C), and the battery did start gradually warming - it was up to about -7.5°C when I left it.

    A couple more notes:

    The Techstream did not show a valid ambient temperature in the battery ECU display when the car was OFF - I guess that's coming from another ECU that's not powered. So that would suggest it's going to be relying just on battery temperature for the heater algorithm.

    The battery heater gets shut off when My Room mode is enabled - maybe any time the car is not OFF.
     
    #24 KMO, Jan 8, 2024
    Last edited: Jan 8, 2024
  5. vvillovv

    vvillovv Senior Member

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    Car Scanner lists battery inlet temps in the app. I mention it because the first winter (which was before DrPrius supported Primes) I kept a ceramic space heater in the cabin to use while charging. The cabin got nice and warm, much like summer temps, but when DrPrius started supporting the Prime I found out that none of that heat was making it back into the battery case. I was bummed, because the heater doubled the electric from the wall during charging. But it was nice to get into a toasty warm cabin even with sub 0 F temps. But I could also fell every draft making it's way through the firewall and by about 10 miles all that warmth was gone.

    Apology bout not getting the details of your testing right, I do agree that the 8 Amp charger setting is not really needed, especially in newer Primes, but I think it will be invaluable when the car and pack start to show their age in a few years from now and the pack internal resistance starts to show up / fluctuate more. Even at 6 years old I've already seen IR get wonky, and there are ways to settle it back down, if an owner takes the time to figure out how to.
     
    #25 vvillovv, Jan 8, 2024
    Last edited: Jan 8, 2024
  6. KMO

    KMO Senior Member

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    And the weather this morning had warmed up enough we're now apparently in the too-warm-for-battery-heaters range. +1°C ambient, -1°C batteries.

    Car did a full drive without starting the engine, first time in weeks - boy the buzzing/grinding noises from the heating system are loud though.
     
  7. sylvaing

    sylvaing Active Member

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    Yeah, for a silent car, the heat pump is quite noisy. Same with my Model 3. While stopped when the heat pump is working overtime, my cars make more noise than a recent ICE vehicle.
     
  8. Trollbait

    Trollbait It's a D&D thing

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    Compressors are just noisy devices, and a heat pump trying to heat near the low end of its operating parameters will be working hard.
     
  9. Hammersmith

    Hammersmith Senior Member

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    This thread is getting rid of the last bit of buyer's remorse I had on choosing the AWD HEV over the FWD PHEV. I was worried I would lose a big chunk of the PHEV benefits during the long winters here(up to 5 months of what KMO just went through), and it looks like that would've been the case. If I lived almost anywhere else in the US, the PHEV would have been the better choice, but I'm better served with the AWD and the extra $4k bucks or more in my pocket(if I could've even found a PHEV near me configured the way I wanted at anything close to MSRP).
     
  10. sylvaing

    sylvaing Active Member

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    I'm in Canada and our winter usually starts in early December and lasts until early April (those are the time the bike stays indoor). Our daily average temperature in December is -9°C to -2°C, January is -14°C to -5°C, February is -13°C to -4°C and March is -7°C to 3°C (yeah!). So, for those months, the average temperature is mostly above -10°C, so I can go without the engine. I think for me the PHEV is still a better fit than a HEV, especially since I have a BEV to compensate for when the temperature gets really cold. Keeping the vehicle heated while it's -20°C and I'm shopping is a game changer for me.
     
  11. Hammersmith

    Hammersmith Senior Member

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    On average, I'm actually a few degrees colder than you, but our winter starts at least a month earlier. My November is only a degree or two warmer than your December. And my December is within a degree of your January.

    I basically have five months where the average high temp of the day is +5C or below. Seven months where the average low temp of the day is +3C or below.

    Why the hell do I live here? lol
     
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  12. KMO

    KMO Senior Member

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    Today's observation - ambient temperature (according to car) -5°C. Coolant temperature readings -7°C or -9°C. Battery temperature around -13°C.

    Temperatures had been below -15°C for the last week, so hadn't been bothering to plug it in - it was still at about 80% charge, with the battery hardly used in the last week

    Plugging it in now, it did start the battery heater, and a slow charge (-4A battery flow indicated, so about 1.1kW). Presumably it will be capable of pure EV today, after warming.

    Edit: Going to drive later, car was fully charged, and batteries preheated to +5°C or +6°C. Quite happy to run in EV mode, and returned from 30km or so with batteries at +13°C.
     
    #32 KMO, Jan 21, 2024
    Last edited: Jan 21, 2024
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