Small solar charger system...

Wow you mean somebody did a study on this? Sorry just funning ya. Not looking to have a argument here only trying to help the ones who are unsure about a DC system. Put a Trimetric 2025 or 2025 RV on your system it will tell you if the batteries are in shape or just surviving. Just look at the average system a lot of people don't know and just install from the instructions. From what I have observed very few systems are using large enough wire for getting the volts that are available from the panels to the charge controller and then to the batteries. The equipment is installed to far apart and the wires to light to get the batteries full. Figure your wire losses and voltage drop Bigger is better when choosing wires. It will be a real eye opener. Keep it short and as close to the batteries as possible. Really the only monitor you need to install in the coach area is the Trimetic meter and keep that away from a heated area (Fridge)if you can. Put everything else as close to the batteries as possible but out of the gasses from the batteries, don't want that corrosive stuff on the electronics. One more thing cheaper charge controllers are not getting high enough voltage to the batteries to TOP them off, that means you will replace your batteries more often and get less out of your system. Keeping everything as close as possible will help with that. 400 watts of panels and 4 Six volt batteries are plenty for the average boondocker some want more some less. Always fuse protect your systems. My money comes the hard way and I want the most bang for my buck. Just trying to help here. Don't kill the messenger. Have a great Day! One more thing use a Hydrometer for checking the specific gravity of the cells and a chart will tell you the health of your batteries.