Like every good Northerner, I've had jumper cables in my car trunk for decades. I've seen ads for cables that you plug into the cigarette lighters of both the stalled car and the car providing the power. Supposedly, it takes a little while (? 5 minutes) to build up enough of a charge to start the stalled car. Note that I'm not talking about a battery-powered device; this is just a cable, and the current comes from the car that is running. QUESTIONS: Has anyone ever used these things? Do they work? How long did it take to get the stalled car to start? Are there any safety precautions to observe? Will these gizmos work by plugging cables into any power jacks in the two cars ... e.g. the jacks in the rear seat of a van where kids plug in their DVD/Bluray players? The presumed advantages of these cables are their much smaller size and the reduced likelihood of frying electrical components by making incorrect connections under the hood.