Just so I understand 12v charging

i think he's right

 

Yes, he is right. But it really charges the 12v battery at 13.6v very rarely in my experience. I will make a count see what is the frequency, but I suspect it is less than 5% (1 in 20) of the times. The rest of times, it only maintains the 12v battery at 12.7v. Never really top it off.

 

I am a recent Prius prime owner , got my 2022 on the 31 of January , living in Québec Canada . This winter was very cold , so I activated the battery heater device . and kept my car plugged on the EVSE since the battery heater operates on 12VDC when needed if the car is plugged in the EVSE.. My charging current is set at 12 amps at 120vac . I observed an interresting event one morning , the temperature was around -20C , the traction battery was fully charged from the night before but the EVSE charge light was ON ....battery heater was operating..I could hear a buzzing sound coming from the front of the car . It was not the heatpump because i did not use the clim prep.
I presume it was the inverter charging the 12vDC battery and also powering the battery heater.
any comments ?

 

Yep, your observation is correct. Although I don't know exactly how the traction battery heater works, it does turn on as needed even after the traction battery is fully charged, as long as the charging cable is still plugged in. When the battery heater is working the charging indicator at the charging port and EVSE "brick" will illuminate green. This function will use some electricity and may cause a delay in fully charging the traction battery. If it was already fully charged as in your case, then the traction battery heater function will sporadically turn on as long as you keep the charging cable attached, and provide power from the wall as needed. The manual says it only does it up to 3 days but we have a report that it was still operating after 5 days.



According to the manual, the Canadian and Alaskan models of PP have another feature called Hybrid battery warming control. I have not actually read anyone reporting on this functionality and explaining how it works. The wording of the manual is very vague and lacks a precise mechanism involved in this feature.



As an experiment, I have turned off the battery heater function on my PP parked outside since Jan. From this experiment, It is now clear that the traction battery heater uses the wall electricity to operate. Below is the record of the average "full-charge" kWh used. As you can see Nov and Dec average is much higher than Jan and Feb average because of the traction battery heater operating. BTW, without the battery heater, the cold-soaked battery takes much longer to warm up when the car is driven. Thus this causes a longer period of the engine-only operation even when the traction battery is fully charged. Other than that, I did not see much difference with or without the battery heater.

 

Thanks for your insight much appreciated
AFAIK for the Alaskan and Canadian model , it seems to me that when the 3 days delay is expired it kiks in an additionnal 31 days of the same function of the battery heater.
I cannot leave my car 31 days in my driveway i am addicted to drive it at least every 2 days

 

That would be a reasonable explanation. I and most others on this forum have been baffled by the language, "It automatically insulates the hybrid battery (traction battery) in extremely low temperatures." Also, the manual clearly states that "This control operates after the charging cable remains connected to the vehicle for 3 days and “Traction Battery Heater” automatically stops." It sounds like the Traction Battery Heater stops after 3 days just like any US model, but a different function "Hybrid battery (traction battery) warming control" operates in Canadian and Alaskan models. No one has documented or observed such a function so far. So, this Hybrid battery (traction battery) warming control function remains to be a mystery to us all.

 

Being a retired electronic maintenance engineer and dealing with Japaneese technology, I had to decipher Jenglish ( Japaneese -english) technical papers and in my humble opinion , just adding a few lines of code for the Canadian an Alaskan market is quite easy and it uses the original code for all production worlwide as for battery heater function

 

Yeah, we need someone in Canada (or Alaska) with PP and someone in the US with PP in a very cold climate like mine, to experiment by keeping the car parked in cold temp and connected to a charging cable for longer than 31 days and monitor the wall charger activity, electric draw, and battery temperature changes (and maybe the 12v battery health). Ideally, it should be done at the same location side-by-side with Canadian and US model PP, but that would be difficult.

We already know that the US model connected to a charging cable for 5 days kept the battery heater functioning beyond 3 days. So, I am not sure if there is really a difference in code between US PPs and Canadian PP. Besides, the side effect of keeping the charging cable connected for longer than a few days is that it will drain the 12v battery quicker. So, I really don't see the benefit of having this battery heater functioning beyond 3 days up to 31 days if that is going to cause the 12v battery to die.

 

Hummmm, I understand your concern , but this time , for now , I do not know all the implications of keeping the car connected and the incidence of discharging the 12 volts quicker..
Dealing and communicating with Japaneese enginnering is a humongus task . Corresponding with the Japaneese culture is delicate.even in an enginering world.
Toyota Us, or Toyota Canada could pitch in.

 

Yeah, I have never kept my PP plugged and parked for longer than a few days max. But as you can read on the thread linked below, the 12v battery in the PP and in Gen4 Prius suffers from chronic "parasitic draw" of about 85mA. Even under the best condition, at ambient temp in subfreezing, the 12v battery is not likely to last longer than a few weeks when undriven. I have been monitoring the 12v battery in my PP over the winter on daily bases, and making sure it does not go below 12.2v. With warmer weather upon us, the most of worry is over for now. But I may experiment again next winter for a prolonged period of plugged charging cable and its effects on the 12v battery. That's if I still have my PP next winter. I can even get the baseline read during the warmer period if I anticipate not driving for longer than a week. The only thing is that with the gas price still being in the record-high territory, we are driving our PP exclusively over our SUV. I don't think I will have a long enough period to test the effect of the plugged charging cable on the 12v battery any time soon.


See this thread for more information:
Hopefully, ultimate 12v battery charging system discussion on PP | PriusChat

 

Thanks for the link ,this has been very informative discussion and also very pleasant
Have a good day

 

Hi again
After reading the thread provided by Salamander King and thinking about the parasitic draw measured , leaving the car connected after being fully charged , the manual invites you to disconnect the plug from the vehicule.
I think that when you have the car plugged in , the Proximity Pilot signal communicates with car the preventing it to move and permitting it to latch the plug by energizing the solenoid to lock the gun in the socket . So this could increase the parasitic draw . So in clement weather where there is no use for activation of the battery heater menu I would disconnect to minimize the drain from the BMS .
In my 1974 Camaro parasitic draw was minuscule , only the car clock was sucking energy from the huge 12V battery

 

That is at least one of the functions that drain the 12v battery while the charging cable is plugged. But there are other computer-related monitoring that happens when the charging cable is connected and uses the 12v battery. The smart lid and connector locking system for the charge port door and charging cable is present in the higher trims not in the LE model in the US. You can disable the smart key using Carista. I have tried it. But the result was that it did not slow the 12v draining that much.

Yeah, all modern cars have tons of electronics that did not exist in 1974. According to this blog by Noco, what used to be considered a normal draw is no longer valid for today's car. Less than 50mA draw when parked no longer applies.
Blog - Parasitic Battery Drain