I have one like Brulaz's, only with 25 amp maximum. I find it works great. It is an amp, volt, and amp-hour meter. The other readings can be interesting but it is the amp-hour amount of charge or % of full charge displays that tell what I need to know.
There is a little problem with mine; it has only small screws to connect the wires carrying the main current. The maximum size wire I could connect is #14. Okay for me; it has never reached 10 amps in or out. Looks like the 100 amp version has a separate shunt that can handle heavy wires.
