I bought this Auto Meter 6391 Cobalt Digital Voltmeter Gauge, obviously, to monitor the charging system in my truck. My 1989 Nissan pickup only has an idiot light to indicate a problem, and I wanted a better way to ensure my alternator was actually charging my battery, and that the battery was holding a charge. After using it for a few weeks now, I can say I've not had any problems at all. The indicator is large and bright enough to see even in broad daylight. It has a lead to connect to the vehicle's lights, but I haven't hooked it up, and don't know why I would ever need to. I checked a local trucking supply house for this meter, and the best they could do was order it for me for $135. I got it from AutoPartsWAY for around $88 plus shipping. There are cheaper meters out there, but this brand seems to have a good reputation, and like I said, I've had no problems at all. I'm very happy with this meter.