I'd heard that the Prius will discharge excess electricity to keep from overcharging the battery, but had never experienced it. Today I was stopped at a light and the car was idling funny. It was as if someone was hand-cranking the engine without the engine firing. It did this for about a minute. At first I didn't know what was happening. Then I looked at the energy screen, and sure enough the bars were full and green. Then I realized -- the Prius is discharging the battery! It's cool how the Prius protects the battery from deep discharging and overcharging.
