Does charging in extreme cold accomplish anything?

Discussion in 'Prime Plug-in Charging' started by EdPalmer42, Dec 7, 2019.

  1. EdPalmer42

    EdPalmer42 New Member

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    I've only had my Prime for a couple of months, so I'm still working out the subleties of EV vs. Hybrid vs. ICE.

    Where I live, winter temps are guaranteed to go below -30C, even in the daytime. Obviously, the ICE will start when I start my Prime. So the Prime will basically be running in hybrid mode rather than EV mode. Under those conditions, is there any reason to plug in the charging cable?

    The manual talks about the traction battery heater and implies that it operates with the charging cycle. Does that mean that once the battery is charged the heater turns off? I'd like it to operate like a 'block heater' for the traction battery to help keep it warm on those cold winter nights.

    Ed
     
  2. Marine Ray

    Marine Ray Senior Member

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    Don't know if this will answer your question but around 3minutes in this gentleman explains the traction battery heater operation. If you doesn't answer your question you could probably contact him.
     
  3. Salamander_King

    Salamander_King Senior Member

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    Our winter temp is never that cold, but I have had no problem charging my car in a few sub 0F (-18C) temp down to maybe -25C nights outside without any ill effects. But -30C daytime high is another story. There are a few warnings in the manual about operating the car under "extremely cold" (-30C and below) condition. It may not be possible to start the car under those temperatures. Do you keep your car in a garage where the temperature is higher than outside? Once you start the car, the cabin heat will bring the traction battery temperature to a safe operating range. If you have any charge in the traction battery, it should be able to run EV albeit very short.


    Screenshot 2019-12-07 at 10.00.03 PM.png
     
    #3 Salamander_King, Dec 7, 2019
    Last edited: Dec 7, 2019
  4. vvillovv

    vvillovv Active Member

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    Ed, I've read that at least one other PC member (besides myself) uses a space heater in the cabin during frigid temps to help keep the pack warm. I think he is in Alberta or Saskatchewan and also mentioned that for him locally, most if not all charge stations also provide a normal 120 volt outlet that can be used to power the space heater while charging.

    If you chose to try the space heater while charging a couple of tips are:
    find a 3 wire flat pigtail extension and cover about 2 feet of it with duct tape, than it can be safely placed under one of the back doors.
    At home don't try plugging in both the EVSE and the space heater on the same 120 volt circuit.
    Avoid plugging the space heater in while it is turned on, simply knock the space heater over so the safety switch turns it off before you plug it in or unplug it.
    Adjustable heat and fan speed knobs are nice too, but not essential.
     
  5. john1701a

    john1701a Prius Guru

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    That battery-heater alone is reason to stay plugged in during "extreme" cold. For those who experience intense winters (for me, that's Minnesota), it means theplugged-supplied electricity can be used far more than you'd expect. Notice on the following video how, despite the outside temperature of -1°F (-18°C), the battery-pack is kept at 55°F (12°C). That means it can be taken advantage of still. Watch the % for the charge-level in the detail provided by the following video:



    The coldest extended duration I have experienced without plugging in was Christmas 2017. We were out in Wyoming celebrating with family. Sitting there for over 8 hours in -9°F (-22°C) unassisted meant only minimal electricity from the battery-pack would be available. (Lithium chemistry experience a increase in resistance when its temperature drops below freezing, hence heating it for better draw & charge efficiency). The system started just fine. I obviously let it warm about for a few minutes before driving, but there was nothing else special needed... only some patience.

    For those who experience ordinary winter, the battery-heater means you'll be able to squeeze out as much electricity efficiency as possible. You still driving in full EV mode until the entire EV capacity is depleted, as this video shows in detail:

     
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  6. EdPalmer42

    EdPalmer42 New Member

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    These are all good answers, but they don't quite hit the mark. I have read the manual - all 1000 pages! I know how to charge, but I don't know why I'd want to charge. I'm looking for info that goes beyond the manual. FYI, I live in an apartment. I have an outlet to plug the car in and a switch to turn it on and off, but no garage, carport, or anything similar.

    Let me try rephrasing my question....

    In warm weather you charge the battery so you can drive around and not use gas. In cold weather, the ICE will start and use gas regardless of what you want so are there any other benefits to plugging in the charging cable? After all, it's a bit of a nuisance to deal with the EVSE. It will be cold, stiff, wet, and dirty. Normally, there would be snow around the connector, but I bought a boot to cover the port and connector.

    The manual talks about the traction battery heater, but the info is confusing and incomplete. To quote the manual:
    1. "When the outside temperature is low" -- How low?
    2. "When the charging timer is used" -- What happens if the charging timer isn't used? No heater or full time heater (i.e. battery blanket)? Does the heater turn off when charging is complete?
    3. "It automatically insulates the hybrid battery" -- sarcasm/ Oh, really? What does it do, wrap the battery in a cozy blanket? /sarcasm Seriously, what are they trying to say?

    The manual describes how the system can cool the battery under high temperature conditions. But, they don't extend that to warming the battery under extreme cold conditions. I realize that most owners won't need such tricks, but since it's a software feature the cost to provide it would be almost zero.

    vvillovv, yes, I live in Saskatchewan. Temperatures here can get stupidly cold. We had an extreme case some years ago where for almost a week, the daytime high was below -40C. Hello to Alaska and the Yukon - I know that's 'balmy' for you. We're all 'balmy' for living in this weather, but that's another topic! At the time I was driving a Honda Civic that was about 10 years old. I plugged it in for a couple of hours overnight and it had no problems dealing with the cold.

    The problem with the 'space heater' idea, as you said, is that you can't plug in the EVSE at the same time. Also, AFAIK, there's no way to get the battery fans to turn on and pull warm cabin air through the battery. They're only used for cooling the battery.

    john1701a, the quote above says that the Traction Battery Heater only works when the EVSE is plugged in. Are you saying that's not the case? It wouldn't surprise me that they made a change to the firmware and it didn't make it to the manual.

    Ed
     
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    I don't have experience with the cold weather with my Prime (only my 2010 Prius and it worked fine but of course it's a different battery chemistry).

    I would suggest that if the engine comes on, leave the battery in the HV state but use an engine block heater instead to reduce wear on the engine and of course help the engine warm up faster (I understand it won't reach operating temperature unless you go for a long drive that isn't on the highway... but note there is an active grille shutter that can help reduce heat loss from the engine).

    However, if it will dip below -30°C overnight, I would suggest leaving the car plugged in. Li-Ion chemistries don't typically like cold weather below -30°C and a cold soak at -32 or -34 for 8-10 hours might be long enough to bring the battery temperature below -30°C and you may have to wait for the battery to warm up before starting off. In that case, leaving it plugged in can help warm the battery up prior to departure (you can still use the same Departure setting in your Charge Schedule so that the battery doesn't stay full).
     
  8. Elektroingenieur

    Elektroingenieur Senior Member

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  9. Salamander_King

    Salamander_King Senior Member

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    For temperature below -30C, as discussed above, it may be beneficial to keep the car plugged in to keep the battery heater function. As for the usefulness of the battery charge is that if your price of electricity is not high, no matter how short the EV range is, you can get more miles on pure EV. In my case, our electricity rate is very high. Currently, EV drive on wall charge costs just about the same or little bit more than running my car on HV using gas. For this reason, I did not charge my car for the entire month of Feb last winter. But after that month, I started again charging my car, just so that I can reduce the use of gas for my commuting even though I know it was costing me more to charge and run the car on EV. So, it is up to you, if the battery heater function is not needed, you can leave the car uncharged and keep driving HV. But if you have any chance to charge your car cheap, there is nothing to lose, except a bit of inconvenience as you have described.
     
  10. m8547

    m8547 Active Member

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    1. It automatically turns on when the battery temperature drops to around freezing and turns off when the battery reaches a few degrees above freezing, as long as it's plugged in. Apparently that continues for 3 days, but it's not clear what happens between days 3-31 if you have a Canadian model.
    2. I have no idea how the charge timer affects the traction battery heater, but maybe they mean that it pre-warms the battery before it charges?
    3. I have no idea what this means.

    I've seen the traction battery heater run when it's only moderately cold. Sometimes when I unplug my car in the morning the green charging light is on, even though it's fully charged, which means the traction battery heater is running. I would definitely suggest plugging it in whenever possible, since the hybrid system can work most efficiently when the battery is above freezing. For example if the battery is too cold, regenerative braking will be severely limited, so you'll lose efficiency from that.

    I've noticed that the battery retains heat fairly well. It is often still 10 degrees F above the overnight low temperature if I park it without plugging in overnight, if I drove it the day before. If you drive everyday and plug in every night, I don't think the battery will get too cold. Also note that inanimate objects don't care about wind chill. The battery won't get colder than the actual air temperature.

    If you want to do a block heater and plug in, you could set the car to limit charging to 8A. That plus a 400W block heater is under 12A, so OK for one 15A circuit.
     
  11. EdPalmer42

    EdPalmer42 New Member

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    Thanks Elektroingenieur, that's helpful.

    So instead of 'insulates' or even 'isolates', a better choice of words would be 'disconnects'. Now that suggests that if you leave the car charging for 3 days in extreme cold, Toyota will actively disconnect the hybrid system at some unspecified temperature. I won't likely run into this situation, but I might try to keep it in the back of my mind.

    Well, since there have been message threads of Primes running at -40C, hopefully mine will be able to as well. :)

    Ed
     
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  12. EdPalmer42

    EdPalmer42 New Member

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    Unfortunately, it's tricky to determine exactly what that charging light is telling you. One of its meanings is that 'Charging is possible'. That would make sense if you had a charge schedule set. After charging is complete would the car still say that charging is possible? :unsure:

    I'm retired so I will rarely use a scheduled charge and I probably won't be going out every day. That's why I'm trying to figure out exactly how this beast reacts to the cold. I need to know precisely how the charging works so I know what to do and when.

    I agree competely with your comment on wind chill and inanimate objects. Unfortunately, when I'm talking about temperatures of -30C, that's air temperature - wind chill goes down from there! :(

    The block heater could be the reason that the 8A option was added. Unfortunately, I suspect that many owners don't know or care about it, plug in both the EVSE and the block heater, and then complain to Toyota when the breaker blows. I saw at least one message thread that said that there was a block heater recall a while ago that reduced the power from 400W to 200W. I checked mine and found that it's only 165W! More like a hand warmer than a block heater. :mad:

    Ed
     
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