My Prime is set (I think) with EV auto on (square box lit) and driving mode to normal, so IT should always run on big battery until exhausted 0%. We have had really cold zero and way below zero weather, so now I noticed that the engine now starts instead of running on traction battery only. I read on this forum that the Prime's car heater is a combo air conditioner/heat pump unit depending on what cabin temperature is required. I am guessing the ICE is running to heat radiator water that runs to the cabin heater (and big battery??) to supplement the heat pump, because the outside air is too cold to extract heat. Am I correct or have I got something mis-set in the computer(s)?
Well, first of all, you posted this in the Gen 1 Prius Plug-in forum rather than the Prime forum. They are very different cars. As to the question, it's behaving as described in the manual and in loads of posts here. The heat pump is only good down to about +14º. And, if you hit the defrost button, that starts the ICE immediately. Also, if it's too cold, the traction battery can't provide enough energy to meet your power demands.
Thank you Jerry. I thought I had this under the Prius Plug in Prime forum. My bad, but hope moderators could move this to the correct heading. So it was what I suspected that when too cold the heat pump can't function. I will grab my owners manual again to find where it states what you summarized.
Just click the "Report" button under your original post and you can have a moderator move it to the Prime Technical discussion. I'd guess that's the best spot for it. There's a ton of great stuff in the manual, but it does take a while before everything you want to know will stick in the brain. I'm always looking up stuff. I downloaded the PDF from Toyota's owner's website and have it on my computers, my iPad, and my phone. IIRC, there's a section that tells reasons why the ICE might come on when in EV mode. It doesn't claim to cover everything, but it helps.
The ICE will start below -14°C/10°F for heat. There is a noticeable difference in heat even at just below freezing between EV mode and HV mode (obviously engine heat is a lot stronger). I assume you mean EV mode? EV Auto requires manually selecting it every time you start the car. If you did mean EV Auto, it'll be interesting to note if the ICE comes in sooner (i.e. higher air temperature or if the climate control was set to a higher temperature) than in EV Mode.
Tideland quote: If you did mean EV Auto, it'll be interesting to note if the ICE comes in sooner (i.e. higher air temperature or if the climate control was set to a higher temperature) than in EV Mode. Tideland, Every time I start car the EV auto has the square lit so I assumed that meant the EV auto mode was enabled. The manual seems somewhat confusing to me as to setting it so it will always run in battery mode with noted temperature exceptions herein. Thanks
Are you sure it says EV/AUTO and not just EV? According to the manual that doesn't happen. (It doesn't say so here, but if there's no EV range available, it'll go to HV, but not EV/Auto ... since there isn't EV range available.) Page 87 from the 2017 manual. I can't imagine they changed this.
Here is detail about zero degree weather... video I captured earlier this week (here in Minnesota) and published just a few minutes ago for a discussion exactly like this.
Nice! It acted very similar to how my PiP behaved when we took it to Ohio and did some driving there with temps in the single digits. (Except, of course, the maximum EV speeds.)
I double checked that whenever I start car, the ECO MODE lights and to its right, EV MODE within lighted square. When I press button the square turns off, press again and square relights. Perhaps in really cold weather the Prime computer decides this is the mode to use? But at least I now know why car is running ICE.
