The idiot lites for battery status are worthless. For decent battery life you want to be sure the battery doesn't discharge below ~12V. It's easy to plug a "cigarette lighter" meter into the 12V auxiliary port. I did, and it works pretty well.
But when solar charging or draining the battery, it's nice to know the actual current supplied/used. I installed this gadget and am quite happy with it. Lets me monitor voltage, charge and discharge current, and Ah.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
The instructions are TERRIBLE chinese-english, and the cable supplied is only ~6 feet. But it does work. Check my Amazon 3 star review for more. This Victor unit is better, I'm sure, but $200 vs $40 was too steep for me.
https://www.amazon.com/Victron-Energ...=AERMGYAT5R869