Hi all, I recently changed my commute and noticed that my 2023 Prime would consistently start its gas engine for a brief period while in EV mode. This happens near the start of my commute, during a maybe half mile downhill stretch. There's a stop light about halfway down the slope - if it hits red and I stop, the car tends to stay in EV mode. However, if I hit a green and coast on through, the gas engine will almost certainly turn on by the last quarter of that stretch. During this time: I'm mostly coasting downhill between 35-40 MPH, not accelerating while lightly holding on the brakes. The energy meter is usually showing partially charging. I'm within the first 5 minutes of my commute, starting with a fully charged traction battery and having driven a few blocks on flat roads - the EV range still shows the full estimate more or less. The car has been parked covered and not in direct sunlight. When I notice the gas engine turn on, the dash indicator still shows I'm in EV mode, but the second icon showing it's using EV range disappears. After the downhill portion I merge onto a freeway, and the car turns off the gas engine and reverts back to EV mode within minutes - maybe less than a mile is driven on the gas engine. Looking at the owner's manual, section 2-1 (page 79), the only thing I'm seeing that might apply is that the gas engine might be used "When the temperature of the hybrid system is high. The vehicle has been left in the sun, driven on a hill, driven at high speeds, etc" Surely coasting downhill on regen doesn't get the hybrid system hotter than actually driving at highway speeds up and down hills - which happens in the latter part of the commute and the car stays in EV mode the whole time. The manual is frustratingly vague about how it actually decides to swap modes. Is there too much regen going on with a full battery? Does anyone have an idea if this makes sense/tracks? It's pretty annoying to have the gas engine kick in then turn itself on, inefficiently eat some gas, then turn off before it even properly warms up. Maybe someone with some technical know-how can tell me if there's a way to avoid this? Thanks for reading!
if you start with a full charge, the car has no alternative but to use engine resistance to burn off the extra regen. it spins the engine with the extra electricity, without injecting any gasoline.
I have the same issue with a long downhill run after leaving home. I believe the issue is that the battery is fully charged and can’t take any regen charge. There’s a couple of things that you can try. I have found pre-warming the car, using the phone app, helps, even when plugged in. Or you can try coasting in neutral down part of the hill. Coasting has the advantage of keeping the brakes disks free from rust.
