Hello. New to the Forum. I live in Vancouver Canada, in an area which is quite hilly. I drive a 2021 Prius Prime Upgrade, usually in EV mode and ECO mode. Often when I go down steep hills with a full battery, the gas engine kicks in. With regen braking and without. My only work around is to turn off the car at the bottom of the hill and restart the car. It goes back to EV mode immediately. Any thoughts? Thanks in advance.
Welcome to PriusChat! Yes that’s normal operation as with a full battery, there is no longer any reserve for regen so the car will kick on the engine to bleed off excess charge. (Similar operation for a Prius since inception). It’s usually not using any fuel (just pumping the cylinders similar to engine braking) but it may use a slight bit if it’s the first run since the engine e will continue to run to complete its warm up cycle after you reach the bottom of the hill. It’s preferable to let the engine complete its warm up cycle for the longevity of the engine (esp if you haven’t been running it for a while).
Thanks Tideland. Appreciate the insight. I did notice that in my previous Prius (08) when going down these same hills. It sounded like something was spinning at a very high RPM when I had regen braking on. I guess it was the bleeding of energy. sounds like I should stop turning off the car and let the engine do it’s thing. I just hate burning fuel on these short trips.
Yeah I get it but the tank lasts so long. Mine lasted a year (once it was a full tank, and during covid, it was only half a tank by the 12-month mark) so if I had a longer trip, I wouldn't hesitate running that in HV mode and then using EV to do the short trips back home (or some combination of that).
Or, stop charging the battery all the way to full before heading downhill. Other Prime owners who live and charge at the top of hills have run into this problem too. People who live and charge at the bottom, don't have this issue. Leave a small portion of the battery uncharged, so that regeneration can go into the battery instead of spinning up the engine as a brake.
