Prime may start ICE in EV mode if Windshield Defogger switched on

GT4Prius - I read the same thing and was also concerned because I plan to purchase a Prime.

I reread Danny's report from Japan and then I noticed that the Owner's Manual is written as a warning of what might happen not a guide to what WILL happen. Note the * at the end of the line after the word "suddenly". That connects to the phrase "When traveling in EV auto only". If you read carefully, the warning is not so bad.

As for the last paragraph regarding the window defrosting using the Remote Air Conditioning System, that seems to be referring to using the new heat pump not the window defroster which WILL turn on the ICE. It is saying that in some situations the heat pump might not work as well as we would like. I will be using the heat pump as much as possible and hopefully that will be often.

Calling the heat pump a "Remote Air Conditioning System" seems strangely accurate and a bit odd. It is basically running the air conditioning system backwards. When the heat pump is delivering warm air, the heat exchanger by the radiator gets cold (and can freeze) instead of getting hot as it would with cooling the car. What is accurate about both operating modes is that they are conditioning the air.

 

It's referring to remote control of the AC system through Safety Connect.

And, power may well be limited due to the charger not having enough power to run the heating system.

 

Think about how a window defroster works in a conventional car or in a regular Prius.

It pumps heat from the ICE coolant through the air conditioner evaporator coil with the AC running to dehumidify that air. That means the heat and the air conditioning are on at the same time.

If the heat comes from a heat pump instead of the ICE, and the AC comes from that same heat pump running the other way, how are you going to do both functions at the same time?

I can see two options - use resistive heat and run the heat pump for AC. I don't see any indication the Prime has a resistive heater.

Or you can cycle between the two - a little bit of time on heat, a little bit of time on AC. That would have reduced effectiveness (reduced "power").

When driving, it starts the ICE so it can get heat from that source while running the heat pump as AC. But they don't do that when plugged in.

 

not if it's only remote a/c as bhtooefr suggested.

 

why would you want heat and a/c at the same time?

 

More dehumidification capability. Use AC to remove water from the air, then heat the air back up to reduce humidity further.

 

Because dry air (AC removes moisture) will defrost way faster than wet air. So, you want dry, hot air for defrost purposes when there's fog on the inside of the windshield.

 

doesn't sound like a big deal to me. just hit floor/defrost on the vent direction button. you'll have heat, defrosting, and stay in ev. i do that know, but there's no heat. and leave the derost switch off whether driving or preconditioning.

 

That will work as long as the air in the car isn't full of moisture. Since exhaling pumps moisture into the air, just having people in the car will result in a very high moisture content of the air in the car.

 

Oh, boy, is that not true.

I keep my car in an insulated garage. I never need it at the beginning, and I always have it on auto. Yet, it's incredibly common for me to turn on the window defoggers during my trip to work. Dozens of times a year, I'd say.

 

It happens whenever it's cold. The windows cool down while driving until the moisture in the air inside the car starts to condense on the inside of the windows. Only if it's both cold and very, very dry does it NOT happen. And live in one of the driest climates around (Colorado) and it happens here frequently.

 

Better compromising EV than compromising safety.
When switching front window defogger I want defogging and quick which means, as others pointed out, cooling and heating the incoming air. This is the best way to defog quickly.

 

Or if there is still snow on your shoes.

These are the hybrids without plug. All the heat from the cabin comes from the engine, which leaves the A/C compressor available for drying the air, and the system likely did so to prevent fogging of the windows. To put another way, you had the system blowing warm, dry air, just not on the windshield.

You also may have been able to get better fuel economy with the A/C light off.

 

The A/C compressor is powered by the HV battery in earlier Prius.

(this is the Gen2, the A/C inverter is discussed at 14:10)

My guess is that Toyota sized the charger to be near the limit of battery charging. With no other loads it would work with no slow down. If you add other loads, (and A/C is a large load on it's own) either the battery charging will slow, the loads will have reduced power, or both. Toyota is promising a charge time, so I bet they resist over promising and instead limit power to other loads. Just a guess. (Then 'May' would mean that defogging is fine after the battery is fully charged but impaired if the battery is still using power from the charger)