Traction Battery Heater stops after 3 days, why?

Discussion in 'Prime Main Forum (2017-Current)' started by Synergy3221, Jan 9, 2019.

  1. Synergy3221

    Synergy3221 New Member

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    Hello,

    I live in MA, so winter temps can get a bit cold. I take the train into work Monday - Friday, as such the Prime usually sits in the garage plugged in, and for any errands we usually take the Tesla. After reading through the manual it states that:

    ● When the charging cable is removed from the vehicle or remains
    connected to the vehicle for approximately 3 days, the system
    automatically stops

    Why does this system stop after the third day? The heater system is pretty low draw electricity wise from watching the WeberAuto deconstruction of the Prime's battery pack. That would mean if on Sunday night I get home, plug in the Prime, wednesday night the Battery Heater no longer operates and it's left to succumb to temps lower than 31 degrees (WeberAuto youtube channel states that this is the temperature where the system turns on)

    I can't for the life of me think why Toyota would make this decision.

    I've thought about on wednesday night unplugging it, then plugging it back in to maybe "reset" the battery heater.

    Thoughts?
     
  2. m8547

    m8547 Member

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    No idea why. Toyota's decisions are often inexplicable. In Alaska and Canada it runs for 30 days, but it can get just as cold in the lower 48 sometimes.

    How about using the charge timer to set it to finish charging just before you expect to drive it? I suspect charging will run the heater if needed, but the manual isn't clear on that. And charging will generate its own heat as well.

    It doesn't hurt the battery to be below freezing if it's just parked. It's not ideal for it to be below freezing if you are going to drive it, but the car must have a way to deal with it because it has to work as a hybrid too, and could likely be parked somewhere cold unplugged. I sometimes wonder how even HV mode can work if the battery is extremely cold, since it is a lithium battery?
     
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  3. jerrymildred

    jerrymildred Senior Member

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    @john1701a, you've done a lot of testing in the great white north. Any thoughts on this one?

    As for how HV (or even EV) can work when the battery is cold, it works fine. Cold just makes it less effective, not non-effective. My PiP had considerably less range in subfreezing Ohio last winter when we visited family up there. But I still got stellar gas mileage while I was there and could plug in. Something like 100 mpg on the little trips we were taking.
     
  4. Salamander_King

    Salamander_King Senior Member

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    I often wondered about that too. I don't have the answer, but in the manual immediately following the section on “Traction Battery Heater” there are those notes.
    traction battery warming control.png
    I understood this means, after "3 days" the PRIME goes to Hybrid battery warming control mode by automatically insulating the hybrid battery and continues in this control mode up to 31 days. Now, the problem is that it says, this function is for Alaska and Canad only. Is that mean, vehicle sold in Alaska is different from the ones from lower states? Moreover, how does this insulation work? I have no idea. It's confusing, to say the least.
     
  5. m8547

    m8547 Member

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    I thought that charging the battery when it's below freezing could cause damage. I know the car can adjust the braking to limit regenerative braking, but the way the CVT works I'm under the impression that at least one of the motors always has to be involved. That means it always has to be either using power from the battery, or charging the battery so the HV capacity is not depleted. Maybe the battery can take a little charge even if it's cold, but the charging rate just has to be limited? I think there is also a rare mode where only the engine is powering the car, but I haven't seen it.

    Is the plug-in-prius the only other Prius with a lithium battery? Or maybe some of the 4th gens have it too? It's rumored that the AWD Prius retains the NiMH battery for better performance in the cold, since it's more likely to be used in cold places.
     
  6. smyles

    smyles New Member

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    I think it's because Toyota assumes that the vast majority of owners either drive at least once on 3 days span, or don't drive for weeks, so why waste? Yeah yeah there always will be someone with a unique scenario/life style/whatevwr, but we're ralking about 95 percentile here.
     
  7. sam spade 2

    sam spade 2 Senior Member

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    One reason might be that moderate cold is NOT bad for a battery.
    It will only experience a slight TEMPORARY loss of capacity.
     
  8. jerrymildred

    jerrymildred Senior Member

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    People up north do that daily. I do it while visiting the north in the winter. No damage. I used to live in Colorado. I know it gets below freezing there. Do you not drive in the winter?

    Which demonstrates that charging in freezing weather doesn't hurt it.

    Not so much a mode as a condition where the engine load and the battery achieve just the right balance. I've seen in on my displays hundreds of times in the Gen 2 and the PiP.

    All Gen 4 Prii have Li-ion batteries except trim 1 and 2.

    Not a rumor. It's mentioned in the test drives and reviews that have been shared here on PC.
     
  9. Trollbait

    Trollbait It's a D&D thing

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    I think insulate is being used here to mean protect from, not as providing a physical insulation.

    Speciality chemistries aside, charging Li-ion when the electrolyte is below freezing, the battery will be damaged.

    Now, just because it is freezing out, that does not mean the battery is actually that cold. Then charging at a very slow rate until the process heats up the electrolyte prevent damage. It appears this is what the PiP does. On top of that, there is the unused buffer in the battery. A tiny level of damage from freezing charging may not be noticable to the operator.

    Is the specifics of the different warming modes known? The 3 day one keeps the battery above freezing temps, but the month long one could allow it to get colder. It could just keep the electrolyte from physically freezing, for example. The manual does warn against operating the car when the temperature is -40.

    I've also seen power flows with nothing going to or from the battery in the gen2. Likely not ideal to do all the time for efficiency, but available to avoid battery damage. You also don't want to charge or discharge if the pack is too hot.
     
  10. Salamander_King

    Salamander_King Senior Member

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    Maybe... but still does not explain why this function is any special. It sounds like very passive like doing nothing to warm-up the battery, and why it is for Alaska and Canada only. The manual states that the control stops 31 days after the charging cable is connected, so what happens then?

    Here is the text from the Manual again.

    Hybrid battery (traction battery) warming control (Alaska and Canada only)
    This control operates after the charging cable remains connected to the vehicle for 3 days and “Traction Battery Heater” automatically stops. It automatically insulates the hybrid battery (traction battery) in extremely low temperatures.
    ● This control stops 31 days after the charging cable is connected, even if it is still connected to the vehicle.
    ● When this control operates, timer charging settings are ignored and charging starts immediately.​
     
    #10 Salamander_King, Jan 11, 2019 at 3:05 PM
    Last edited: Jan 11, 2019 at 3:21 PM
  11. Trollbait

    Trollbait It's a D&D thing

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    I pointed out the manual saying operation at -40 or lower is bad for the car, and after rechecking it, it says not to leave the car out at that temperature. It also says not charge when the temperature is -22f/-30c, or damage will occur to the charging system.

    There may be a temp at which the battery is damaged regardless of use or not. That could be the purpose of this extra heater, or to allow use of the car in hybrid mode from a start without damage to the battery.

    For the 31 day limit. Not plugged in, likely to keep the battery from discharging to low. Keep in mind there are over systems drawing on the battery, like the protection circuit, and self-discharge going on. For plugged in, I can only think of as a failsafe to keep the heater from cooking the pack. Then it could be designed with power outages in mind.

    As for why Alaska and Canada only, I can only think of regulations for those markets if the system is just a difference in software. Yes, parts of the lower 48 can get as cold, but parts North can get colder still. Cold that make engine, battery, and fuel heaters are a need, not a convenience.
     
  12. sam spade 2

    sam spade 2 Senior Member

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    But.....the freezing point for a battery likely is WAY lower than for water.
    For a fully charged lead acid battery, that is something below -40F.
     
  13. Trollbait

    Trollbait It's a D&D thing

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    Freezing used in this discussion refers to the freezing point of water, which in the point at which charging a Li-ion can cause damage.
     
  14. john1701a

    john1701a Prius Guru

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    Nope. The only issue with below freezing is it reduces efficiency. The losses are rather substantial then, which is why the charging ramps up slowly if you start with an extremely cold battery. This is also why the pack has a warming feature, for gen-2. The previous generation didn't have that, but no big deal. It resulted in less efficient use of the electricity, but no harm. Mine worked fine in Minnesota for 5 winters before I sold it to a friend who is still using it 2 years later, no big deal.
     
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  15. bisco

    bisco cookie crumbler

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    which explains why the heater shuts off after 3 days :unsure:
     
  16. Trollbait

    Trollbait It's a D&D thing

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    "Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a sub-freezing charge. This is permanent and cannot be removed with cycling. Batteries with lithium plating are more vulnerable to failure if exposed to vibration or other stressful conditions. "
    Charging Batteries at High and Low Temperatures – Battery University
     
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  17. sam spade 2

    sam spade 2 Senior Member

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