Power Management

Thought I'd drop a note about something that many of you may already know but my enthusiasm and impression of my Prius' downhill performance is what I think, noteworthy.

The wife and I were on northbound I5 in California yesterday. We were leaving Los Angeles and headed up to San Francisco. Right as I5 leaves the LA basin, you cross through some 4000+ foot high mountains that are the result of tens of thousands of years of activity on the San Andreas fault. Well, the run was 57 miles across and at the north end as you come down the mountains you run into a 6% downgrad that runs 5 miles.

Okay, so as I started the run I had the foot completely off the accelerator and was letting the traction braking/charge the HV battery scheme do its thing. That didn't last too long as the car kept accelerating so I engaged 'B' or the engine braking mode. That worked quite well at keeping the downhill speed nicely at 70mph.

As I coasted in 'B' mode for a few minutes all was as I should expect - quiet, consistant coast downhill. Then about 2-minutes into this I could hear the enginge revving up quite high in speed. I hit the mode button and noticed the HV battery at at full charge and realized what the electronics was doing was to rev the engine speed up to increase compression forces and use the engine to brake the car in lieu of the tractions braking/charge mode because the battery was fully charged and overcharging the battery was not a good thing.

As I continued downhill with the engine revving quite high and in 'B' mode, I gently pushed on the accelerator pedal a fracton of an inch - just enough that the car in normal traction braking mode would drop of out that mode and go into a coasting mode - the engine would rev back down to idle and the car would begin to start pick up speed. I would take my foot off the pedal and the engine would rev back up again.

To summarize, I thought this behavior was quite impressive and I came to the realization that the Prius engineers really did do their homework and engineered features into the electronics that makes this car what I consider one of the most technically advanced vehicles of the time.

Okay, back down from the podium and I say thanks for reading this.

Don