 I purchased the C-Max Energi with the thought of driving the vehicle only a few miles per day, plugging it in at night, and almost never having to visit a gas station. The big problem with that is the lithium ion battery is charged, but the 12 volt battery which initially cranks the engine isn't being charged at the same time. So what happens? You go out to start the car, and the 12 volt battery is dead because the 12 volt is gradually being drained. The local dealer said that's the case because the Energi has no alternator. So if you don't drive extended miles every few days or so, the 12 volt battery will gradually be drained. This happened twice to me. 