01-11-2009, 10:39 PM
Dakota wrote:
I am looking for the source of that "extra" energy. So braking is it? If you take away breaking, is it an even trade?
They also save by not idling the gas engine, it can be shut off.
Coasting and going down hill get the best mileage, the gas engine can shut off, and the battery can charge down hill even if you're not braking.
At stop lights, the engine can shut off, and the electric engine gets used when the light turns green, and the gas engine can then start up while you're already moving if needed.
I don't know if you can really measure if it's "an even trade" because the car doesn't operate that way, it will use the gas engine to directly power the wheels when that's the most efficient thing to do (it also charges the battery as it's powering the wheels). There is a lot of computer control that decides when to use the gas engine. I think about the only way to get the gas engine to come on just to charge the battery without also moving the wheels is to have the car stopped with the air conditioner (all electric) running for a very long period of time.
One limitation that I run into is the size of the battery, from my house there is a 3 mile down-hill stretch, and the regenerative braking will fully charge the battery before I reach the bottom, so that time from when the battery is full, until I get to the bottom, I'm generating energy, but there's no place to store it, so it's being wasted.
(I'm referring to the way the Prius works above, because that's what I own and understand best).