any meter you get needs to checked against a voltmeter... So you know where 75 and 50% discharge are. The led gauges are like gas gauges in so much as they tend to read full, full, full, then when they drop one or two leds you are empty. A voltage readout gauge is like having a voltmeter connected all the time. They do need a voltage supply to run, many of the cheap ones on ebay are 5v operating system... If you go digital get one that runs within a 6 to 12 volt range and follow the install instructions carefully. The led is simpler but needs to be calibrated to use it properly. We all know better than to trust our battery investment to an idiot light
