I bought one of these this winter and rigged it today with my little 15 amp solar panel. Works pretty cool and relatively inexpensive. Tracks amp hours down to three decimal points. I rigged it with quick disconnect plugs between the controller and battery terminals and got a much more revealing set of data than I can with just my multi-meter, including: cumulative amp hours, amps, voltage, watt hours, etc. Its fun to adjust the panel and see exactly the change I may or may not be getting given the angle of the panel to the sun and what happens when a cloud drifts by. It also revealed how "cheap" my little controller is as it would never kick out more than 12.78 volts . I recommend it to those of you who like to mess with solar and don't already have a more sophisticated "shunt" type meter. This does not use a shunt.
Amazon.com: "Watt's Up" RC Watt Meter & Power Analyzer WU100 Version 2 --- SALE!: Toys & Games
Rick
Amazon.com: "Watt's Up" RC Watt Meter & Power Analyzer WU100 Version 2 --- SALE!: Toys & Games
Rick