Escapees May June 2015 Demo

13.4 Charge Controller

Shore Power

dc/ac inverter

Generator ac

Charger/ Converter

“Solar panels make it possible to charge the batteries without shore-power electrical hookups.”

for extended periods of time, the bigger the battery bank, the better. The limit- ing factor is the weight of the batteries and the space they require, so you don’t want too big a battery bank. On the other hand, almost all RVs are shipped with house batteries that are too small for extended living off the grid. The flow of electricity, or current, is measured in amps, and an amp-hour is one amp of current flowing for one hour. Battery ratings are given in amp- hours, and more amp-hours means the battery can store more electricity. A good size for a battery bank on an RV used for weekends and vaca- tions is 220 amp-hours or more. A good size for a full-time RV home off the grid is 440 amp-hours or more. A general rule of thumb is for the battery bank to store three to four times your maximum daily requirement. So, if you will generally be using 100 to 150 amp-hours of stored power every 24 hours (fairly typical for full-time RVers), the house battery bank should be roughly 450 amp-hours or more. Batteries are designed either to give a big punch of power to start an en-

the tub that is using up the electricity that the batteries have stored in them. That is only one-half of the “solar” equation, even though there is nothing solar about it. Now let’s look at how to replenish the electricity stored in the batteries. RVs are built to charge the batter- ies whenever they are plugged into shore power. Most trailers have an inexpensive converter to do this job. Higher-end motorhomes have a more complex inverter/charger that acts as both an inverter when the RV is not plugged into hookups and as a charging system for the batteries when the RV is plugged in. Solar panels make it possible to charge the batteries without shore-power electrical hookups. Solar panels are rated in terms of “watts.” More total watts from all the panels equates to faster battery charging (filling the tub more quickly). A good size for a weekend/vacation RV used mostly in the non-winter months, when the sun is high in the sky and the days are long, is 100 watts Continued ›››

gine or to provide a long, steady flow of power to keep systems running. RV manufacturers often use Group 24 12-volt start batteries as house batteries, so it is common for RVers to upgrade to at least two six-volt golf cart deep-cycle batteries. Golf cart batteries have the same footprint as Group 24 batteries but are one to two inches taller. There are many other sizes and types of batteries. Wet cell batteries contain liquid that must be topped off periodically with distilled water and metal plates that must be cleaned periodically through a process called equalizing. More expensive AGM, gel, and lithium ion batteries don’t have those requirements, and they don’t have to be installed upright ei- ther since there is no liquid that might spill out. Charging the Batteries— Solar Panels So far, we have discussed making your RV’s batteries capable of running your AC and DC household applianc- es. This is all on the “drain” side of

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