For Christmas I received a NPower 2.5 watt Amorphous Solar Panel Battery Maintainer. Some times I don't drive my truck for a week or two, so I thought this might help maintain the battery during the cold weather. You set it onto the dashboard and plug it into the cigarette lighter. It comes with 2 connectors. One for the cigarette lighter, and one with battery clamps. The problem is, when you plug it into the cigarette lighter, there is no way to know if it made a proper connection in the lighter socket. So I went to Harbor Freight and bought a cheep $6 multi-meter. Now I can disconnect the lighter end from the solar panel, plug it into the cigarette lighter, and use the multi-meter to make sure it's getting a connection. Then plug it together and sit it onto the dashboard. When I first tested it, the meter read 12.3 v. After a couple of days it read 12.7 v. Now to see how it does..