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Traction battery heater question

Discussion in 'Prime Main Forum (2017-2022)' 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?
     
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  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!
     
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  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...
     
  10. Louis19

    Louis19 Active Member

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    question about battery heater
    I am trying to figure out what this means :When the charging cable is removed from the vehicule OR remains connected to the véhicule for approximately 3 days , the system automatically stops. (page 136 of the manual)
    Is it saying that that the the option of setting the battery heater to ON will be turned OFF after 3 days if the car is sitting the inactive for 3 days.
    Since I live in Canada it also says .....it automatically insulates the traction battery in extremely low temperatures. This control stops 31 days after the charging cable is connected.
    So if iI understand it correctely when the first control kicks out after 3 days a second control kicks in for 31 days if the car is connected
     
  11. Ovation

    Ovation Active Member

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    I have used it consistently this winter (coldest January in Quebec in nearly 20 years). I once had it plugged in for about 80 hours during a particularly cold stretch and the heater was still working when I unplugged to leave. I simply presumed my Canadian spec’d car was ready to keep doing it for 31 days.
     
  12. BlackSmith451

    BlackSmith451 New Member

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    Does it matter if the current is MAX or 8amps?
     
  13. john1701a

    john1701a Prius Guru

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    I wouldn't think so. The draw is much less than that for just maintaining an above freezing temp.
     
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  14. BiomedO1

    BiomedO1 Senior Member

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    It doesn't matter. The Prime's current draw is limited to 12A on L1 and 16A on L2. The car's internal system will simply delay/turn-off wall charging and draw off of traction battery - if it requires more amps to do something (ie. heat or cool the cabin).
    Last winter, I turned-on my bathroom heater. It's on the same 20A circuit w/GFCI as the L1 car charger. It tripped both circuit breaker and GFCI. I knew the GFCI would pop, but was surprised the 20A breaker also popped. The next weekend, I wired-up a separate 30A L2 circuit for the car.
     
  15. Louis19

    Louis19 Active Member

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    IIRC the battery heater in the Prime draws around 200Watts as explained in the Weber University video
     
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  16. 2wheeler

    2wheeler New Member

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    So is it better to have the battery plugged in every night during very cold weather even if you don't require a charge? or worded another way, which is worse for battery life, leaving it plugged in while the battery is full and leaving the battery at full charge for long periods of time, or having a cold battery for a few nights when the temperature plunges but you've still got 85% charge remaining?

    This choice happens a lot in cold weather (below -15C) because I primarily use the engine to heat the car and not EV mode.
     
  17. Tideland Prius

    Tideland Prius Moderator of the North
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    If you’re in hybrid mode, then you might as well leave the battery at 85%. Charging only helps with keeping the battery warm and ready to go and with scheduled pre-conditioning of the cabin (heating in this case).

    Also, it means the engine has battery buffer to charge while it’s idling/warming up. (If you’re at 85%).
     
  18. Louis19

    Louis19 Active Member

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    I think that your battery should be plugged in every night in polar temperature.
    Having the battery heater option ON and when plugged in..the BMS will ckeck the temp of the Traction battery and will heat it if needed.
    Keep in mind that the heating circuit is derived from the 12Volt battery system so the on board charger has a double function : It rectifies the AC from the plug supplying power AND it supplies proper level of DC voltage for the Traction Battery . It also has an additionnal DC to DC converter to power the 12 Volts system hence the battery warmer and also the 12 volt battery . Keeping the traction battery and the 12 volts battery happy is welcomed in polar temp.
     
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  19. Salamander_King

    Salamander_King Senior Member

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    My understanding is that the battery heater will only come on if the traction battery is going to be charged. If it is already fully charged as questioned by @2wheeler , I don't think the battery heater will turn on even if it continues to be plugged in. The manual indicates that the Canadian and Alaskan version of PP has different cold climate function than the lower US versions, but I am yet to find out what exactly is different. For the experiment, I kept my traction battery heater option OFF last winter. There was no observable difference in my PP's performance. I can't say for sure if it shortened the longevity of the traction battery or not, but if it did, it is still less than 5% in the first 13 months. Which was not much different from the rate of degradation for my other PP which had the traction battery heater option kept ON all its life.
     
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  20. Trollbait

    Trollbait It's a D&D thing

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    To see which treatment of the battery is better would probably take years to become notable, and then it could be because some uncounted variable.

    That said, the danger to the battery when the cells are at 0C is when it is charging. Nonreversible damage can occur with lithium metal plating of one of the electrodes. Discharging at those temperatures will be at reduced performance, but not a risk of damage. Discharging will also heat battery up. Leaving a mostly charged battery unplugged in such temperatures shouldn't be an issue.

    Also keep in mind the concept of thermal mass. While the car is in use, the battery heats up on its own. It likely reaches a temperature higher than the cabin. The cells don't rapidly lose that heat when the car powers off, and there are layers between them and the outside. The battery could still be warmer than air temperature in the morning.

    Having the battery full all the time in the cold also shouldn't be an issue. That is more of a concern in hot climates. A fully charged battery that is heated up essentially goes into an overcharged state, which is bad for its health.
    That only works while the battery is charging. Once fully charged, power from the outlet is cut off, and the 12V system is powered by the starter battery. The 12V draw is actually higher with the plug in as the system is monitoring the connection. the manual warns against leaving the car plugged in for long periods for this reason.
     
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