Daily charging

Have you set the traction battery heater option to "OFF" on the vehicle setting option on MID? That is the way to turn it on or off. While I still do not understand why Toyota would give an owner an option to turn off this feature, the default setting is ON. So, if you have not changed the setting you have the battery heater option ON.

I have not tried changing this option to turn OFF the traction battery heater, but my understanding is that if it is set to OFF, then it will take much longer to finish charging because there is no active heater turned on. I have read that the Pip has no active traction battery heater and it has to wait until the battery warms up on its own to start full charging.

 

I just realized that the Owner's Manual statement I just copied had a statement negating my assumption. It says the Traction Battery Heater may operate after the charging has been completed. Hmmm,,, that means keeping the plug up to 3 days is better than removing it immediately after completing the charging when it is extremely cold? It's only up to 3 days, because according to the manual unless the car is built for Canada or Alaska, then the traction battery heater automatically turns off after 3 days. Now, that brings me another question, are the PP sold in Alaska built differently than in lower states? What if someone buys PP in lower states and move to Alaska? Can it be modified to be a Canadian version?

 

Sub-Freezing temperatures cause electrical resistance to rise significantly for lithium chemistries. Basically, you can't draw or capture as much electricity. The system knows that and protects the pack... preventing damage. You can still use the battery. In fact, I drove in temperatures well below freezing in only EV with my PHV and there was no damage. It keep chugging along for year. In fact, it still is.

I'm not sure who that is... no one I know. My recharging for the entire time I owned my PHV (from Feb. 2012 to Apr. 2017) included a recharge at work. That's twice per day 5 times a week. An extra charge sometimes took place on the weekend too. With my Prime, I did the same thing until the pandemic.

 

I have not changed the setting. I’ve only noted it is accessible.

According to the excerpt you posted, it stays active for 31 days if plugged in on a Canadian/Alaskan model. I can’t speak to your question about converting to this mode but it does raise a potential conundrum. If staying plugged in after a charge is complete poses a problem for the 12v battery, wouldn’t staying plugged in for 31 days in cold temperatures be an automatic death sentence for the 12v battery? Seems like a significant contradiction.

Also, if the default setting of the batter heater is ON then I should not be able to set a scheduled charge time (if that page is correct per the note below the 31 days function). However, I have successfully set a scheduled charge at temps below -10C on more than one occasion.

 

Thanks for the explanation. Yet, I am still puzzled as to how the Traction Battery Heater (TBH) works. As I understand, Pip does not have the TBH and PP Traction Battery Heater option can be turned OFF. In Pip and PP with Traction Battery Heater turned off, how is the traction battery protected from the damage when the charging cord is plugged in during sub-freezing temperature?

Also, I am still not clear when the TBH turns on. The manual is clear that it may turn on even after the charging has been completed. What purpose doe it serve if the charging is already completed? Finally, I am even more puzzled as to how the Traction battery warming control for Canada and Alaska models works.

WTH does it mean "It automatically insulates the hybrid battery"?

 

Yep, that's why I am even more puzzled by the Traction battery warming control for Canada and Alaska models as stated above.

The statement from the manual says "timer charging settings are ignored and charging starts". My take is that you can still schedule the charging, but the timing of charging may no longer follow the schedule.

 

Chances are, if you can plug in the traction battery charger, you can also plug in a 12V battery charger.

 

True. But nothing in the manual remotely suggests one should do so. It’s still puzzling.

 

The entire section of the manual describing the Traction Battery Heater and Traction Battery warming control (Alaska and Canada only) is a total mystery to me. It makes absolutely no sense as to how it functions and how one should use them. From the wording, it sounds like Traction Battery warming control for Alaska and Canada only is a distinct feature that takes over the Traction Battery Heater after 3 days if plugged. This makes me wonder, what happens to non-Alaska and non-Canada models, what happens after 3 days if the car is still plugged in?

 

Based on the blue highlights in the first attachment, should I plug in my Prime overnight (going down to -15C) despite it having a full charge? And if heating the battery depletes it a bit, should I schedule a charge for sometime tomorrow afternoon in order to make sure the heater works? Or should I just let it sit (was planning to go out and run some errands but there’s been a change of plans)?

 

It isn't necessary. Mine spent a Christmas in Wyoming without a plug, with several nights at -23°C. It was no big deal, even warm-up.

Having the plug warm the pack means more from it sooner.

 

Thanks for the info. Have to confess I’m not quite sure what you mean in your last sentence.

 

The battery will try to provide EV quickly, rather than just assist. I have seen battery temps in the low 50's even when parked outside in sub-zero F temps when plugged in.

That effectiveness of Prius Prime battery warming makes me quite curious how bZ4X will be handled. Toyota knows the LFP reputation for cold-weather was quite poor in China. Of course, with a $4,500 vehicle selling like hotcakes, you can't expect anything for thermal management. It's an interesting opportunity for an automaker to get to witness another automaker take a chance like that. From Toyota, I suspect we'll see rather aggressive from-the-plug battery warming.

 

I had the 2017 PP for 3 winters. During those three winters, I just kept my routine of plugging in after coming home and set the charging schedule for departure at 6am daily. That way during the coldest time of the day, the traction battery was being charged (thus warmed) and had minimal time with a full charge and charge cord plugged in after the completion of charging. But that was my pre-pandemic routine when I was commuting to work every day 18miles each way. During winter, I usually started the car in HV even though the battery was fully charged, and used the engine to heat the cabin for the morning commute saving the traction battery charge for my afternoon commute.

I did not drive the 2020 PP during winter due to pandemic restriction and sold the car mid-winter. For my current 2021 PP, I am not charging it every day. I charge the car as needed day or night based on my plan for the day, and I am not keeping the charging cord plugged any longer than necessary to charge the traction battery. I really don't think you need to worry too much about the timing of charging. Just follow your schedule and charge it to have a max amount of charge available for your daily trip.

As far as the evidence of the battery heater operating, I have noticed a statistically significant increase in the charging kWh drawn from the wall after it got cold enough. I have charged my PP in 14F (-10C) or below several times. Each time, the charge took more kWh. But I don't know if it took longer or not, since I am not charging the car on schedule and using "Charge Now" and never checking when the charge has been completed.

Average kWh used/full charge by Month

• Dec 7.06kWh
• Nov 6.73kWh
• Oct 6.68kWh
• Sep 6.64kWh
• Aug 6.71kWh
• Jul 6.76kWh

​

 

Thanks for all the info and follow up. As I plan to use the car tomorrow, I think I’ll leave it alone overnight. It’s not like the traction battery will be full for days on end.

 

Dec. 24 at 6:45 PM was when I last plugged in. At 7:31 PM today... 5 days later... I unplugged. It has been proper cold here in Minnesota lately, hence no desire to go anywhere. This morning when I got up, it was -8°F. That meant the garage kept beverages so cold, there was a good chance of them freezing. Anywho, the graph for my JuiceBox clearly showed activity from time to time. When I checked this morning, the session had drawn 6.74 kWh. Just prior to unplugging, the total had climbed to 7.26 kWh. The heater for the battery-pack was still active despite being well past the supposed 3-day limit.

 

Does your JuiceBox graph show when the battery heater operated last? Was it past 3 days after the charge was initially completed?

I have been noticing a clear increase in the kWh used to fully charge the traction battery after it got cold. This is without keeping the charge cord connected long after a charge is completed, certainly never longer than 3 days after charging. see my comment #35. So, it is clear that that battery heater operates before and during the charging session. The question is after the charge is completed, how frequently and how long does the battery heater operate? And for what purpose does it serve? If the charging cord is unplugged immediately after the charge is completed and left cold-soaked for longer than 3 days at -8F, would the car not have started without having the traction battery heater? I think it would have started with no problem. So, why waste kWh on the traction heater if it is not necessary?

 

Here's the data from last night (just after I noticed the charging light was on) and this evening.

 

So, from the data, you can't tell when 0.52kWh (7.26-6.74) of electricity was used after the initial completion of the charging on 12/24 at 3:34pm. The draw could have happened a day after or every day or 3 days after? Meaning my initial question has not been answered.

To non-Alaska and non-Canada models, what happens after 3 days if the car is still plugged in?