Energy monitor - odd behaviour

If your electric motor is powering the vehicle, there are two things that would activate the ICE (internal combustion engine). If you accelerate quickly the ICE may turn on to assist powering the vehicle. Another reason the ICE turns on is if the windshield defroster is activated or the climate control is set to a temp that requires cabin heating.

 

In addition to what was just mentioned the ICE will run for a multitude of other reasons including hybrid battery temperature, a slight increase in power demand (which might occur if you aren’t using cruise control and you subconsciously apply more pressure to the accelerator; or will occur if you are using cruise control and it accelerates the vehicle or compensates for wind drag that you wouldn’t necessarily be aware of). Plus many more reasons I’m sure others will mention. It’s not actually unusual behavior.

 

In all Prius ( that I'm familiar with ) there is a spot in the engines rev range (rpm) where there is neither regen or assist and the car rolls without using power from either the engine or the motor. Gen 2 owners described it as heuristic mode. With a regular Prius like yours, it's rare that the engine wouldn't be providing power to the wheels at 100 km h.
Sure if you are going down a hill or on the downside of an overpass, that's when the EV portion of the monitor can display EV being used while driving normally at 100 km h.

I may not be understanding what you're describing about the monitor, but at first read it looked to me like it was backwards when talking about the engine and electric motor displaying on the monitor.

 

I don't understand your issue as in the video the engine on the left side of the car pictogram is always on, sending power to the wheels and every now and then extra not needed power to the battery and it take energy from the battery on the right hand side of the pictogram every now and then. All normal for the speed you were travelling at.

The engine runs at set optimum revs for fuel consumption, so sometimes at a set revs it would send all the power to the wheels when needed and other times, if the wheels don't need all the power from the engine, then it would send some to the wheels and the excess power to the battery to charge it. Hope this makes sense.

 

Sorry I see now in your first message you did mention that you noticed the engine is constantly on. However your second message "appreciate both responses, but the time the ICE is being used is less than a second. " is confusing as the ICE is on the whole time.

You will notice the ICE is on the whole time with power going to the wheels. Now the hybrids run their engines at set revs where they can control the fuel consumption optimally.
So in your scenario at 101kph, the engine needs to provide a certain amount of power at a set revs to keep the car at speed with all the power the engine can provide. When you go down a little bit of a dip gravity helps the car, so the engine stays at the set rev's providing the same amount of power, but the excess power (because gravity helps) is sent to the battery. This keeps happening every now and then, so that is why you see the arrow flicking from the engine to the battery so quick. That's situations where the road helps the car. Others like little rises in the road causes the engine's power at the set rev's to not be enough to maintain the speed so the car augments the lacking engine power by drawing from the battery&electric motor.

It is not changing modes, that is how hybrids operate, Ice, ICE+electric power and sometimes only electric power, that's Hybrid mode.

 

I think you will be happy with yours, they are excellent cars, just change oil at 10 000km intervals and it will keep going. I had a 2011 model here in Christchurch for 10 years and did 120 000kms trouble free. Sold it in a weak moment.

Just bought a 2019 Prius Prime (plug in version) from Wellington in September and very happy with it. 1.9l/100kms on current tank at 950kms with only a quarter of a tank (15l) used - can't complain about that.
Anyway happy Prius motoring.

 

heretical mode is a term coined by some Gen 2 Pruis early adopters. It's not an easy concept to understand. Toyota has dialed in assist and regen so much since Gen 2 that it's almost impossible to detect in Gen 4 unless you know what to look for. You found it in your PiP and sure as "grits ain't groceries and eggs ain't poltry" Wet Willie -it was one of those gestalt moments.
And if you're into it, you might want to see if you can reproduce what you saw on your screen there, at slower speeds in both EV and HV modes. cheers