ICE runs in EV Mode only in cold weather

It’s 0F in Palo Alto, California? That’s part of greater San Fran, right? Or you’re currently elsewhere?

 

Quarantine school must also start early.

I'm sure we'll get more details soon.

 

Ah, that’s true. 6 am’ish.

 

At temp below 14F, the heat pump will not work to heat the cabin, so if you had HVAC set to heat the cabin the engine will come on even in EV mode. Yeah, at 0F you need all the heat the engine is producing and otherwise wasting. At that low temp, I usually switch to HV manually to save the EV range for later use. Even at that temp, the car will go into EV drive but the engine will come on frequently.

 

On my 2020 Prime, I've found that if the battery temperature is even a few degrees below freezing the computer limits the amount of power you can draw out of it. One good stomp on the accelerator and the ICE starts up.

 

It must be quite a shock going from the Bay Area to Minneapolis in a Prime. It'll really act differently.

Don't hate me, but as for us, we ate lunch outside today at a place about eight miles from home. Had to run the A/C while driving. Still got 5.2 miles/kWh since it was all 35-40 mph.

 

-17c, that's the problem. seat heaters

 

I read somewhere that at -14C or 7F the ICE automatically comes on to protect the battery. That's what our 2018 does. Thankfully we've only had very few of those days this winter (Alberta). Although we're gearing up for a 5 day stretch of -25C shortly!

 

That and there isn't enough heat outside for the heat pump to gather for the cabin.

 

I’ve been able to drive in EV mode in -20C, but if you want heat the ICE will take a loooong time to reach operating temperature. Eventually there are bursts of battery usage though.

 

I "accidentally" started a thread on exactly this problem under another forum, as being a relatively (and I hate my relatives!) new prime owner, was surprised when the engine would start. I reread the owners manual thinking I had accidentally pushed a button that took car out of exclusive EV mode. But now I know why this is happening. All my pre-Prime experience was with regular priuses with engine staring stopping as needed.
This ole dog learned something new!!

 

Since the past weeks have been extraordinarily cold, I have gotten some more practice. Here is what I've learned so far:

• I park in an unheated attached garage, where it never gets colder than -8°C. This is enough to pre-heat the Prius plug-in. So I pre-heat in two rounds.
• The "engine start" temperature seems to be what is shown on the dashboard. This adjusts slowly. Meaning that I can usually start in EV mode, and keep the heat on for a couple of minutes until the vehicle realizes how cold it is. I stop when the meter falls below -10°C.
• If you go long enough without the climate controls on, vater vapor will fog up your window; forcing an engine start for safety. The colder it is, the slower the buildup. Brrr!
• The ICE firing up doesn't seem related to having the climate controls set to ECO or FAST.

 

February is nearing its end, and temperatures have been above freezing for about a week. What a difference that makes when driving the plug-in!

Today I successfully completed a fairly long trip on electricity only. I expect this to be the norm for the next ten months.