Winter Charging Strategy

Discussion in 'Prime Main Forum (2017-Current)' started by m8547, Nov 7, 2018.

  1. m8547

    m8547 Active Member

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    Does anyone have a good charging strategy for cold weather? The way I see it there are two options:

    1. Charge when I get home from work, when the temperature outside is probably above freezing and the battery is probably warm from driving home.
    2. Set a timer to charge overnight, finishing when I need to leave from work. The battery might start out cold, and it might have to use the battery heater, but it will finish warmer.

    I know high temperatures in the summer can actually shorten the lifespan of the battery. Is cold weather the same way, or is it just a temporary effect where the battery can accept/supply less power, and the capacity is temporarily lower?

    Option 1 is probably better if the battery doesn't like to be charged while cold, or if the heaters waste a lot of power.

    Option 2 might be better since the battery is warmer for the drive to work in the morning, so the range is a little longer.

    Maybe it doesn't matter either way, but does anyone have a preferred strategy?
     
  2. bisco

    bisco cookie crumbler

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    doesn't prime have a conditioner before charging?
     
  3. illumiN8i

    illumiN8i Active Member

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    Option 2 is better for the long term health of the battery. Source: Page 133 of the Prime Owner's Manual.
     
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  4. m8547

    m8547 Active Member

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    I don't see anything on page 133, but I did find some information in the manual.

    "Traction Battery Heater” may operate when charging is not being performed." - This suggests it might keep the battery warm after charging is complete (for up to 3 days while it's plugged in)

    "Avoid parking the vehicle in areas with a high temperature under direct sunlight when the hybrid battery (traction battery) is fully charged."
    - It's well-known that high temperatures will damage the battery. Even after driving home in the winter, the battery won't be very warm. Certainly much colder than the same drive after the car has sat in the sun all day in the summer. Does charging in cold temperatures cause damage like high temperatures?

    "Leave a low level of charge in the hybrid battery (traction battery) when leaving the vehicle undriven for a long period of time."
    - It's not good to leave the battery full for a long time

    "In the following situations, the remaining charge of the hybrid battery (traction battery) after charging completes may be less than normal in order to protect the system (the EV driving range after the battery is fully charged may be shorter).*
    ●Charging is carried out when the outside temperature is low or high"
    - This sounds like cold temperatures could be bad for the battery

    Bisco: There is the traction battery cooler cycle that runs under certain conditions when the battery is hot. But it's better not to let the battery get that hot in the first place, if you can avoid it. Similarly, there are battery heaters, but wouldn't it be better to charge when the battery is already warm, instead of waiting for it to cool off overnight then having to heat it up? In the summer I always try to set a charge timer so it will charge overnight when the outside temperature is lower, and the battery has had time to cool off.
     
  5. illumiN8i

    illumiN8i Active Member

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    Lithium-Ion batteries can't be charged at freezing temperatures, and their energy output is reduced in cold temperatures. That's why the heater is necessary. Cold is not a battery health issue like heat is. Cold is a performance issue, Heat is a health issue.

    If you want to learn more, see battery university. It's an excellent resource: Charging Batteries at High and Low Temperatures – Battery University
     
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  6. Trollbait

    Trollbait It's a D&D thing

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    Heat is bad for the battery's life. Cold generally isn't bad for a battery's life, but reduces efficiency. However, permanent damage can occur to a Li-ion pack is charged while the electrolyte is at actual freezing temperatures. The main purpose of the traction battery heater is to get the battery pack up to a temperature that is safe to charge at.

    Now, charging generates heat in the battery. Since heat is bad for it, letting the pack cool down after driving, and it can be quite warm, before charging will be the best practice for long life. But there is more safety protocols built into the system than a charger for your AAs, so you don't need to stress too much over this.
    Define conditioner?

    The Prime has that heater to keep the pack from freezing, and it can turn on the cabin A/C if the battery is getting too hot while charging. It has the means of controlling for extreme temperatures to prevent battery damage. It does not warm or chill the pack to a temperature range that is ideal for efficient charging and extended life, like Teslas and GM plug ins do.
     
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  7. Salamander_King

    Salamander_King Senior Member

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    How does the traction battery heater in Prime work? Does it has to be plugged in? I charged my PRIME all winter long last year always below freezing temp, but did not change any setting. The heater must come on by it self.
     
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  8. bisco

    bisco cookie crumbler

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    i have charged my pip occasionally at close to zero temps over six years with no problems, i have never heard that it has a traction battery heater like the prime
     
  9. Salamander_King

    Salamander_King Senior Member

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    OK, I found in the manual p 126:

    ■ “Traction Battery Heater” When the outside temperature is low and the charging cable is connected to the vehicle, this function automatically warms the hybrid battery (traction battery) until it reaches or exceeds a certain temperature.
    ● When the charging cable is removed from the vehicle or remains connected to the vehicle for approximately 3 days, the system automatically stops.
    ● When the charging timer is used (→P. 147), this function will operate according to the timer settings.
    So, It is totally automatic. Nothing to set. But it must use electric power to preheat before charging begins. That means during winter, the charging time may increase and also uses more kWh for full charge. I don't know if I noticed this but I can't say I measured time and kWh used during full charge in winter and compared to summer time values. I am now curious, how much more kWh it uses for heating. Does anyone know?
     
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  10. illumiN8i

    illumiN8i Active Member

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    While it is automatic, it is possible to disable the "Traction Battery Heater" in the "Vehicle Settings" on the MFD as mentioned on page 127. Not sure why anyone would want to disable it though.
     
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  11. Trollbait

    Trollbait It's a D&D thing

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    It doesn't. Data gathered by those that track charge rates shows that the PiP uses a very slow rate at the start in freezing temperatures. Once the heat by product from charging gets the battery warmed up some, charging gets faster.

    While it likely means more electricity used, charging would take much longer if the Prime used the PiP's strategy for freezing temps.

    Fringe cases like the charge mode. In Alaska and Canada, the heater will keep the working periods than the 3 days mentioned here. If the person isn't going to need the car for some time, why waste electric keeping the battery ready to go?
     
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  12. m8547

    m8547 Active Member

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    So it sounds like it's best to use the charge timer in the winter.

    With the timer it sounds like the heater won't come on until it starts charging, versus if I let it charge immediately it will stay warm all night after it's done charging. It's not clear if the heater will stay on after the set departure time? But the battery will be nice and toasty after it finishes charging, so my range should be a little better in the morning. Plus I can set pre-conditioning so the windshield is automatically defrosted by the time I need to leave.
     
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  13. ed4271

    ed4271 Member

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    This is what I do. I live in Upstate New York where we get a lot of snow in the weather can you drop down below zero. When I return home, when it temperature is in the teens, I may be placed my vehicle on charge. The vehicle tells me that it can it use the traction battery heater. I select the input that says it can use the traction battery heater. The car won't charge until the battery is warm enough to accept the charge. And it's summer time when it's very hot and I've driven on all EV miles the car ask if they can use the air conditioner to cool down the battery. I've had the car since February 2017 and I've been doing this every winter and summer. I haven't lost any degradation in the output of the battery. It's only been 2 years so time will tell. I drive mostly on EV miles except for in the winter time where the mileage goes down to 25 EV miles. Unlike all electric vehicle the Prius Prime does not have a cooling or heating system for the traction battery. It uses a fan to suck in the cabin air to cool and uses the traction battery heater to heat the battery. So I should just just do what you normally would do is plug in when you need the car to be charged to drive on the EV mode. Remember when you're driving in hybrid mode is always charging the battery. Hope that helps

    Posted via the PriusChat mobile app.
     
  14. Salamander_King

    Salamander_King Senior Member

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    While it is always better to use timer to charge, winter or not, I am not sure if traction battery heater keeps the battery warm after the charge is completed. My understanding is that it only works at the beginning of the charging. That said, problem with using timer with L1 charger when you use preconditioning is that preconditioning use traction battery charge and L1 will not have enough power to replenish before you leave. Also, with my experience, AC preconditioning is useless in our winter temperature which is usually below 14F.

    Do you see warning for use of traction battery heater? I have not see that. Also, although I have read in the thread and know there is a popup warning to use traction battery for cooling, I have not yet seen this warning on my car. Our summer temp usually do not get above 85 and I don't think my car has experienced extreme heat that would requires AC to cool the traction battery.
     
    #14 Salamander_King, Nov 8, 2018
    Last edited: Nov 8, 2018
  15. Chazz8

    Chazz8 Gadget Lover

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    I remember reading about the traction battery heater here on PriusChat and here it is; HV Battery temperature control | PriusChat
    Interesting quote; Below each of 5 banks of cells there are two resistive strip heaters, one of which Toyota has labelled "battery heater" and the other "battery warming system".

    Just another improvement for the Prius line that started on the Prime. Can anybody verify that the resistive heating strips were not on the PiP.
     
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  16. Old Bear

    Old Bear Senior Member

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    You may want to settle in and watch this hour-long video about how the Prius Prime battery is constructed. It does a good job of showing the cooling and heating components.

     
  17. m8547

    m8547 Active Member

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    What does it do if you set pre-conditioning and the temperature is too cold (below 14F) for the heat to run in the morning? Does it just not run?
     
  18. bisco

    bisco cookie crumbler

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    can't prove it, but it hasn't ever come up in 6 years, and there's nothing in the manual
     
  19. Salamander_King

    Salamander_King Senior Member

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    I think car still run the heat pump, but have almost no effect on the cabin temperature. I tried preconditioning when ambient temp was ~6F. I had a remote thermometer set at front console to monitor the change in the cabin temperature inside of the car without opening door. The AC was set to 70F AUTO. With this setting, after the overnight charge has completed, I hit the remote AC button while the car is still plugged. The car started drawing current, and the dash light started to blink indicating that traction battery was used and L1 charger is now trying to replenish it. After 10 min of preconditioning, no change in cabin temp. I tried repeatedly hitting remote AC every 10 min, but no change in cabin temp up to 4 times (~40 min). However, after 5th time, I did see a slight rise of a few degree in cabin. For all practical use, preconditioning at this low temp is useless for I would not want to keep pushing the remote AC button every 10 min for 5 times before leaving in a morning.
     
  20. Old Bear

    Old Bear Senior Member

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    With an ambient temperature of ~ 6F, the heat pump is not going to help. I believe that it is only effective down to 14F (-10 C) and that it is necessary to run the internal combustion engine for heat below that temperature.

    heat-pump.jpg

    Cabin temperature pre-conditioning uses the heat pump only -- as it should, because there is no way for the car to know if the car is inside a garage or other enclosed space where running the ICE would be dangerous.

    I hope that your ~6F experiment was conducted last winter. Otherwise, being only early November, I hate to think what the rest of your winter is going to be like.
     
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