This of course results in either charging the batteries to early, too long or not enough. Not being too happy about this (past) situation, I now have had a monitor installed that acts just like a fuel gauge for my battery bank. It is quite a nifty device from Xantrex called Enerdrive eLite that not only gives me current capacity in percentage but also, just like a fuel gauge shows me with bars increasing in height how full my batteries are.
By simply pushing a button I now can scroll between displays showing volts, amps and amp hours consumed. At a glance I can simply look at the LCD bar graph to see a 'fuel gauge' reading of my current battery state.
It sure takes out the guessing game, gives me a good indication how much longer I can go on current consumption until I need to recharge. It also shows me how many Amps are going back into the batteries during charging, being it shore power, solar panels or generator. Sure makes things a lot easier.
Digital Display to show battery volts, amps, amp-hours, state of charge. Easy to read LCD bar graph, 'just like a fuel gauge'. Around 99.5% accuracy of battery status. Flush mount face place, with fixing by rear locking nut. Compatible with 12 and 24 volt DC systems. Includes 500amp / 50mv Shunt. Can be programmed to work on any battery type, with capacity up to 2000+ amp hours.