Possible long downhill scenarios
Thanks, Robert, for your many thoughtful posts. You and Graham give such clear technical depth to the discussions for those of us with scientific or engineering bents.
After reading Graham cover to cover, it does appear that the Prius does blend in engine braking, spinning the engine with no gas consumption. At least that is better than wearing your (in the Prius case, light duty) brakepads out. A little like a Jake Brake?
Anything that uses up electricity would help slow you down, too, I assume, such as A/C, radio, whatever that would absorb regenerated energy that exceeds the battery capacity. (Unless, of course, using A/C causes the ICE to fire up, that I don't know).
My main concern is that, since the Prius has reduced the brake system weight/duty due to regenerative braking, if you happen to do a lot of long upgrade, long downgrade driving, such as on the San Francisco to Tahoe run and back, you might wind up less efficient, and more importantly, need to keep an eye on brake wear.
Graham says that the regenerative braking is low efficiency. Any approximate quantification, Robert? Like about what per cent of the energy expended in accelerating is recaptured?