Solar Power for Your RV
Solar Charge Controller
You can ’ t just plug solar panels directly into your RV house batteries without some way of controlling the charge . That ’ s because you ’ ll likely overcharge and damage your expensive RV batteries in a few weeks of unattended sunshine . You need an MPPT ( short for Maximum Power Point Tracker ) solar charge controller that will convert the varying voltage and amperage output from the solar panels to something your batteries can use as the sun changes .
Warning : Some RVs are being sold as “ Solar Ready ” which just means the manufacturer installed a solar panel plug on the side of the RV and ran internal wiring over to the battery compartment . Don ’ t be tempted to hook up these wires directly to your RV batteries without a charge controller because of the risk of overcharging your batteries . Often “ Solar Ready ” just means the wiring and connectors were factory installed . It doesn ’ t mean you can just hook up the wires to your battery and plug in portable solar panels . You absolutely need a Solar Charge Controller .
Solar Charge Controllers not only need to match the amount of solar panels you plan to install , but also be capable of charging your battery types . While all of them can be set to charge FLA ( Flooded Lead Acid ) or AGM ( Absorbent Glass Matt ) batteries , some may not have a setting for Lithium ( Lithium Iron-Phosphate ) batteries . So make sure they have an Li setting . If not , then you won ’ t be able to charge your expensive Lithium batteries to more than 80 % SoC ( State of Charge ). But I believe that all modern solar charge controllers do have a Lithium Battery setting .
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Battery Banks – chemistry and sizes
Here are the basics for selecting batteries for camping .
First of all : If you ’ re going to add more batteries ( and you will certainly want to do that for boondocking ) all batteries have to be the same chemistry , size , voltage and ( in a perfect world ) age . Trying to add a Lithium battery to an existing FLA or AGM battery will not only compromise the performance , it could even damage the charging system . So if you ’ re going with 2 or 4 or 6 batteries , they really should all be purchased at the same time and properly connected .
While FLA ( Flooded Lead Acid ) batteries may be the cheapest to purchase , they ’ re usually not your best choice for boondocking . That ’ s because they shouldn ’ t be discharged to below 50 % SoC ( State of Charge ). So if you have a 100 amp-hr battery , you can only use 50 amp-hours of its charge without severely shortening its life to maybe one camping season from its expected four or five camping seasons . Also , FLA batteries should have their water level checked monthly and topped off with distilled water . Allowing a FLA battery to get low on water is the quickest way to kill it .
AGM Batteries are a better choice since they don ’ t require checking or adding water . Plus they don ’ t out-gas Sulfuric acid fumes like a FLA battery , and those fumes have to be vented out of the battery compartment . And unlike an FLA battery , an AGM battery won ’ t boil over and leak Sulfuric acid onto the floor of your battery compartment which will rot out any metal or wood rather quickly . Some AGM manufacturers claim that their batteries can be discharged below 50 % SoC without damage , giving you more useable energy for a given amp-hour rating . However , discharging any AGM or Flooded Cell Battery below its recommended SoC will reduce its life . But in the long run AGM batteries are probably a better choice than traditional FLA batteries if your budget will allow , just because of reduced maintenance . Continued on page 30
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