Escapees May June 2015 Demo

don’t get overcharged. Similar to turn- ing the knob on the tub’s water faucet to make the water flow either at full blast or at a slow trickle, the charge controller controls the flow of current into the batteries. Charge controllers are rated in terms of the maximum amount of current they can control and the maximum amount of watts in the solar panel array, and they must be installed as close to the batteries as possible. For small weekend/vacation RVs, a 10-amp or 20-amp charge controller will do the trick. For full-time RVs camping off the grid long term, a 60-amp or larger charge controller is needed. Buying a larger one allows for the addition of more solar panels down the road. Larger charge controllers use a multi-stage charging system for the batteries. First thing in the morning, when the batteries are most depleted (perhaps around 12.3 volts), they put the batteries in a bulk charge state, let- ting the current flow from the panels at full blast. Of course, until the sun is high in the sky around noon, full blast may not be that much.

“...hair dryers, toasters, small pancake com- pressors and power tools, vacuums and microwaves can all be powered with an appropriately sized inverter, battery bank and solar panel installation.”

or more. A good size for a full-time RV used for many continuous months of living off the grid, even in winter, is 500 watts or more. Solar panels come in many sizes, and the limiting factor on RV roofs is physical space. It is vital not to let any shade fall on the panels from rooftop appliances like the air condition- ing unit or trees or buildings. A few square inches of shade on a panel can shut the entire panel down. A typical full-time RVer choice is four 140-watt 12-volt panels. An alternative is to use fewer, but bigger, 24-volt panels, for instance, two or three 255-watt panels. Smaller 12-volt panels fit into smaller spaces on the

roof. Bigger 24-volt panels can be in- stalled using thinner gauge wire, which is cheaper and easier to cut and bend. A general rule of thumb is to “match” (roughly) the number of amp-hours in the battery bank to the number of “watts” in the solar panel array. For instance, 600 watts of solar power would be matched with 600 amp-hours of battery storage.

Charging the Batteries— Charge Controller

The solar panels will send as much current to the batteries as the sun al- lows, but sometimes this is more than the batteries need. A charge controller protects the batteries and ensures they

16 . ESCAPEES | May/June 2015 | www.escapees.com