Has anyone used them? I think the biggest problem is that the cigarette lighter is only powered on when the key is in the ignition, however would these work if my battery died and left it in the car for a few hours to charge the battery with the key in?

Or should I just get a car battery charger?

The reason I'm asking is because I've been out of town a lot this past fall and haven't been able to drive the S regularly. I believe that I haven't driven the S in a month. This happened back in September after I had done a bunch of traveling this summer and the battery was still under warranty. Sears tested the battery and electrical system of my car and everything checked out...

 

I dont think the solar thing is gonna help unless its left plugged in the entire time your gone. Wich as you said wont work. So you might as well just get one of those battery charger things.

 

Well I do know they are really just trickle chargers at best, and I wouldn't expect to quick charge a vehicle battery once you go out and discover it's dead. If you'd like to have it plugged in while the car is sitting there without the key then you should just add an additional outlet under the dash so it's unswitched with the ignition and just leave it plugged in.