I do like Roy. I picked up a DC and a AC volt meter on Ebay for about $6 each including shipping. I installed them on a counter end just inside the entry door with a on/off switch for each. The blue lit meter draws next to nothing and makes for a nice night light. I leave mine on all the time except when not camping.
I have the chart Roy shows, laminated and taped inside a cabinet door and another one near the batteries. Recharge at 12.0, my 3 stage Power Dynamics 9260 does a great job of caring for the batteries.