Is there a legitimate use for charge mode in the Prime?

I'll ask again... What are the GPS co-ordinates of that stretch of hill where the car continues to pick up speed forever without any braking" ? Again, I remind Paul G that the car in question is a 2024 Prius Prime, not some other car. It's being driven in the normal D mode. And the phrase used by Paul G was "pick up speed" forever.

 

There are grades where you will pick up speed forever, even with all the engine braking the car can do—depending on your speed at the start.

For any downgrade, there will be a speed where your energy gain from gravity just equals what the engine can twirl off (somewhere around 13 kW in a gen 3, anyway), and engine braking can just manage to hold that speed steady. Start off below that speed, and there's plenty of engine braking to hold it or slow you. Right at that speed, holding steady is possible, and above it, you'll be picking up speed.

On a tame grade, not much to think about because whatever speed you're likely to drive will be below that critical speed.

On a very steep grade, you may have to choose a speed a lot slower than you'd like to drive, if you want the engine braking to be able to maintain it.

 

Maybe it never happened because someone was actually paying attention while driving. It happens. They likely applied the friction brakes, or is they were smarter, they engaged the engine brake. No one wants to overspeed down a hill.
It is there for a reason.

 

The first time I saw the Energy Monitor graph after going down a steep drop starting at different speeds I called it dynamic regen. That was a long time before I understood anything about how Prius decides which way and how much to use its breaking and / or regen. A lot of owners most likely ever notice those differences.

One difference I think most all of us could agree on regarding B mode is that it doesn't ever use friction brakes. At least not that I've ever noticed B using friction brakes.