Comment est-ce que possible?

I recently had my jeep worked on and was borrowing a pickup truck from another missionary couple here. One morning I was driving to school and it was very dark & rainy. I had turned the headlights on, but once I arrived I forgot to turn them off. Later that afternoon, I came upon a dead pickup. I had another missionary come and jump the pickup. Well, evidently I didn't drive it long enough or far enough, because the battery was dead the next day. When my jeep was fixed the next day, a mechanic friend, brought it back to my home. He tried to jump the pickup again with my jeep, but it wasn't working. He then proceeded to tell me that he wanted to take the battery out of my jeep and put it in the pickup to start it. I asked, "How will I be able to drive my car?" He proceeded to tell me that once he got the pickup started, he would return the battery to my vehicle. I couldn't comprehend that and kept asking,"Comment est-ce que possible?" (How is that possible?) I watched him do exactly what he said. I told him, I would never have believed it, if I didn't see it for myself. Evidently, the battery is only needed to start the vehicle and then the alternator and gas take over. (Of course, none of the electrical things in the vehicle work. So it would not work if you did this in the evening, as you would have no headlights.) I found out later that this happens often. Oh the life in Africa! I am learning new things everyday.