I have been driving my 2019 Clarity for over a year now, I have been experiencing the ICE coming on after a full charge when I press the brake pedal or when I engage the brake regen, regardless of if the car was going downhill or not. I find this frustrating as I would prefer not to have the ICE comes on at all. I understand that the ICE has to come on once in a while, maybe every few days to do a routine check but to come on every time I have a full charge is very annoying and defeats the purpose of getting a PHEV. Does any know how to switch off the ICE so it won't come on or if other PHEV does the same? I took my car to the dealer and on one has a clue how this happen and how to fix it, they admit that they didn't sell a ton of these and no one bothers to send their technicians for training on this vehicle. However, I love the car, it is quiet, smooth, powerful and I only put in $14.25 worth of gas since I owned it (13 months). Thanks in advance for your comments. Cheers.
Actually system check turning on ICE normally only happens after more than a month or two of no ICE usage. Since March I have only had ICE come on twice, both cases was when I accidentally accelerated past the ICE turn on point. Some people who drive exclusive EV will purposely switch to HV briefly (or gun the accelerator) every couple of weeks to activate ICE because they think it may not be good to go more than a month without ICE running.
For most Clarity owners if ICE comes on every few days it's not maintenance mode kicking in it is the other usual suspects, like accelerating too much which is very easy to do without realizing it since the car is so smooth and quiet, and normally when you do accelerate harder than normal it's because you are in a situation that requires it, and your attention is likely on that so you won't be staring at the dash during the moments of hard acceleration. If you were staring at the dash you would likely see the power indicator go past the blue area in the gray area, maybe just a tiny bit, and maybe just for a second, but that's all it takes to activate ICE, and once it comes on it goes through full warmup which can take several minutes. And again if you weren't watching the dash at the exact moment that you blipped it into the gray, you will only sometime later notice that ICE is running and think that it came on completely randomly for maintenance. To remove some of the mystery about whether or not you momentarily accelerated enough to activate ICE you can drive in Econ mode, in that mode the point where you feel it click past the detent is the point where ICE activates, so it helps you be more aware even without looking at the dash whether you have pressed the accelerator far enough to activate ICE.
The other culprit is what you mentioned, if you have a full battery it has no place to store regen electricity, so if you press the brakes it has to get rid of that energy somehow, so it uses the generated electricity to spin the engine, and the engine then starts up, and yep it now runs several minutes of warmup before shutting off. The reason it always does full warmup is for EPA requirement to not have unburned fuel in a cold catalytic converter. However no one really knows why it has to start ICE in that situation, why not just spin the cold engine without starting it, and any additional braking needed can come from the brake rotor. No real explanation it's just what it does. And it will do it every day if you are in that situation which eliminates the idea that it is doing this for engine check reasons.
Only one car that I know of will stay in EV mode as long as you have battery power, no matter how hard you press the accelerator pedal, and that was the Chevy Volt. Prius Prime apparently is close as it is reportedly hard to get ICE to come on through hard acceleration. Hyundai Ioniq reported goes the other direction and ICE comes on easier than it does in Clarity.
I don't agree though that this defeats the purpose. The purpose of a PHEV is to greatly reduce the amount of gasoline needed and the Clarity does that, and much better than most PHEV's. Other than Volt there are almost no other PHEV's that go as many EV miles per charge as the Clarity. Prius Prime for example only goes half as far per charge. The tiny amount of gasoline used in the cases where ICE comes on briefly is trivial compared to the amount of gasoline saved. People who drive almost exclusively EV in their Clarity (like me currently) experience that even though ICE may occasionally come on for a few minutes, you can still easily go many months without the gas gauge moving even a tiny bit. Hardly defeats the purpose, in my opinion it greatly fulfills the purpose. It's only our sensibilities that get rankled because we can't completely control what the car does in terms of ICE activation.