Traction battery heater question

Discussion in 'Prime Main Forum (2017-Current)' started by MMBH, Dec 12, 2019.

  1. MMBH

    MMBH Member

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    Should I choose the option to have this turned on? Under what conditions should I be choosing to?
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    If you leave the car plugged in, the car will run the heater as necessary to keep the battery temperature above freezing (or at least close to it if it's much below freezing) for better battery performance.

    I thought it was automatic (only the traction battery cooler had the message on the screen)
     
  3. Salamander_King

    Salamander_King Senior Member

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    If you live in colder climate, you always want to keep the traction battery heater option ON to protect the Lithium ion battery. My understanding is that it warms up the battery pack to prevent detrimental effect that below freezing temperature have while the pack is being charged. Even if you don't live in cold climate region (i.e. never sees sub-freezing temperature), I see no reason or benefit to turn this option OFF, but Toyota somehow leave this option to the owner. I don't know why.

    Well, the Traction Battery Heater option is user customizable on MID. I don't know situation where you would want to turn it off. I never changed it from Traction Heater ON. I don't know what would happen if I choose NO on this option, and if I try to charge my battery plugged in when it is extremely cold. My understanding is that charging Lithium battery under freezing temp is detrimental to it's chemistry, so why would Toyota give user option to turn OFF this safety feature is totally mystery to me.

    traction battery heater.png
    traction battery heater2.png
     
    #3 Salamander_King, Dec 13, 2019
    Last edited: Dec 13, 2019
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  4. drash

    drash Senior Member

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    Maybe according to the third bullet it might trip someone’s circuit breaker if it turns on while charging.


    Unsupervised!
     
  5. Salamander_King

    Salamander_King Senior Member

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    I think the Traction Battery Heater turns on before the charging starts, but not simultaneously while charging? I would not think it would draw any more than charging it self. I have had my car charging on 15A circuit using OEM L1 EVSE for over two years with the heater option ON in sub-zero weather in winter. Never had the breaker trip. The car is parked outside but the circuit is shared with a freezer, lights, and garage doors opener on the same circuit while car is being charged. Though during charging, there probably no draw from other appliances on the circuit.
     
  6. drash

    drash Senior Member

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    Yeah true for your purposes and mine, but someone might be on a “not as robust” of a line or shared circuit breaker and they’ve actually lowered the charging speed to 8 amps.

    I’d be interested in actual time charging at that power draw just for comparison.


    Unsupervised!
     
  7. Salamander_King

    Salamander_King Senior Member

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    Agreed. But still, why would you want to turn off the battery heater option if you know it can cause devastating consequence on the battery? Under normal operation, the heater would not come on, unless it is needed (meaning it is cold enough). It is needed because the battery may get damaged unless warmed up first before charging starts. In those situation, I would rather have breaker trip and charging to not start than forcing the charging without the battery heater.

    I am not going to try this on my car, but I think if someone turns the battery heater option OFF and tries to charge during below freezing temperate, the car would not charge the battery unless the battery warms up on its own up to a safe temp.
     
    #7 Salamander_King, Dec 13, 2019
    Last edited: Dec 13, 2019
  8. Trollbait

    Trollbait It's a D&D thing

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    With the heater off, the Prime probably works like the PiP. When the pack is cold, a slow charge rate is used until the charging process heats up the pack. I would like to think that if it truly cold enough that damage would occur, the system simply wouldn't charge.

    Your attachment provides some reasons for why someone would choose no, but I don't think they are strong enough to do so. For someone more concerned with wasting electricity(heater comes on when battery fully charged), the health of the pack(full charge reached before departure), or not having full EV range when they leave(charging time takes longer and full charge reached before departure because the pack was hot), they might be.
     
  9. MMBH

    MMBH Member

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    Ok thanks. I didn’t know which option was the “right” one and this helps explain it a little bit better as to why it should be on in the winter. I have a Prime Premium not an Advanced and hence as I don’t have access to warm up the vehicle ahead of time using the app, and usually charge it on demand versus in prep to leave at a given time each day, I didn’t know what was the preferable setting. Thanks again for the explanation on why it should be set to on (which it wasn’t and I’m on year 2 now, so hopefully it is ok if it was off last winter as well...
     
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