Ed wants to buy a solar panel to keep the battery charged. Does anyone know the ins and outs of this theory?

Tags: Faulty RV Batteires, RV Solar Panels

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Hi Maryann,


Are you wanting to install a solar panel to keep the battery maintained during the times your not using the camper, or do you want to install them so you can boon dock?




Ed says boondock (new word for us) and anytime.

Seems to be the least of our worries right now. His batteries keep going dead. -M

   OKAY, Solar panels in general can indeed provide a low rate of charge (a few amps) to help maintain the house batteries, subject to sunlight, their output wattage and how many you have, and their relative angle with respect to the sun. They can greatly extend house battery life for extended dry camping periods.

  HOWEVER they are not a cure all if your house batteries are faulty (have a shop load test them and check specific gravity and electrolyte levels) or theres some sort of trickle discharge (bleed off) causing them to constantly become discharged. If they are running down even with no loads (lights etc) then you need to find the cause and fix that FIRST and Solar Panels are NOT the cure for that (although if youre in the sun it may take longer before the batteries discharge).

  Troubleshooting the cause of a slow trickle discharge involves systematically removing and testing all the 12 VDC circuits one at a time until you isolate which is at fault.

  My experience has lead to some appliances/systems that might cause a slow discharge:

   LP Gas detectors that close a gas solenoid valve in case of gas can constantly draw current

   Some refrigerators can draw current even if off

   Some 12 VDC Smoke or LP gas or Carbon Monoxide detectors constantly draw current

   12 VDC to 120 VAC Inverters sittin running 


  This isnt rocket science but figuring out just which circuit and/or which appliance or system is draining the batteries can be a pain. An ammeter and a voltmeter (VOM) is about the only tool you need. HOWEVER first make sure the batteries themselves arent auto discharging because thay are bad. The new Generation of SMART CHARGERS can greatly extend the life of your house batteries versus the cheap run of the mill OEM Converter Chargers installed in many RV's. If the RV is stored for long periods keep the batteries charged now n then by plugging her in to shore power so the Converter/Charger can work or use one of those slow trickle charge battery maintainers or fire her up now n then so the engines Alternator can charge them. 


  I have a rooftop solar panel and run three paralell 125 AmpHr deep cycle Marine/RV batteries for extended dry camping and I just start the RV every few days if needed so the engines 80 amp alternator can top them off (much quicker then the low amperage from Converter/Charger while running the Genset)


  Hope this helps, Solar Panels are fine and provide some small charge BUT IF YOU HAVE A BATTERY OR TRICKLE BLEED OFF DISCHARGE PROBLEM YOU GOTTA FIX THAT FIRST. 


  Ol John T and all in Indiana

As John said, you'll want to find out if your batteries are faulty.  If you find out they are good, you'll have to find out whats causing them to discharge prematurely.  


A few years ago I purchased two 64 Watt Unisolar Solar panels for my RV.  Those two panels combined with a good MPPT Charge controller would deliver 5+ amps of charge in Ohio's sunny weather.  On cloudy days I could get  2+ amps.    Albeit that might seem small, I never plugged the rig in unless I was using the overhead air conditioner.   


When shopping for solar panels, your going to find there are basically three types on the market.  The three types are multicrystalline (Sometimes called polycrystalline), monocrystalline and amorphous.   


Amorphous panels, sometimes called "Thin Film" technology can be found pretty cheap. Usually these panels are imported from China and can be found at discount stores such as Harbor Freight.   To be frank, these panels give the solar industry a bad name.   Most of these China panels are made of thin glass, weak framing and have a short life. The biggest disadvantage of amorphous panels is the real estate it takes to generate usable energy.   Because of this, you'll find a 45 watt monocrystalline panel is much smaller than a 45 watt amorphous panel.  A typical amorphous panel looks like this:


Monocrystalline panels are made from very thin slices of a very pure silicon nugget.   They are the most efficient solar panels currently on the market.   Multicrystalline panels are also made of very pure silicon, but use peices of the silicon nugget instead of a thin slice. The cells of a multicrystalline panel have a shiny blue foil look whereas monocrystalline cells are usually a solid dark blue.  Both panels usually consist of 36 individual cells.   Both have a very long life expectancy, 30 years and more.   Monocrystalline panels are usually a little bit more efficient and because of this normally cost more than multicrystalline panels.  Typical Multi/Mono crystalline panels look like these:


Usually polycrystalline and monocrystalline panels are made from tempered glass and can handle the rough abuse they'll see on our RVs/Campers.  Because the technology over the last few years has changed, the angle of the panels isn't as critical as it use to be, so you can get by with mounting them flat on the roof.   Also over time they are becoming much more shade tolerant.  


After deciding what kind of panel you want to buy, you'll need a charge controller.   A charge controller prevents overcharging your batteries.   A typically 36 cell solar panel will deliver 22 volts or more.  The charge controller will reduce this voltage to safely charge your batteries.  One type of controller is a PWM (Pulse-width modulation) controller.  These controllers can be found rather cheap and work reasonably well.   There is a fairly new guy on the block called a MPPT controller.   At this point they are very pricey, but they are a better controller and will deliver almost the full potential of your solar panels.    


More information about MPPT controllers can be found HERE.


Also deep cycle batteries do not like to be stored in an uncharged state and over time it will ruin the batteries.    Deep cycle batteries also will bleed off their charge over time even when not being used.    A solar panel will prevent this from happening and will extend the life of your batteries.  


Hopefully some of that information will be of some help.


Thank you all for helping us with the solar and battery situation. Ed is out tracing fuses and power as we speak. You guys are great and Than You again. -M

Hi Maryann,

    Tony and Joy here, we have lived mostly off grid for a few years now...not saying how many..lol  If you want to play detective you can check everything in you unit for power usage.  ie. the water pump draws 6 amps I run it 2 hours a day so there's 12 amps.  The lights I use draw x number ect. ect.  Most all eclectric devises have a tag that states usage.  Sometimes it is stated in "watts". ie. light bulbs.  In order to convert the number of watts from amps you also need to know the voltage. Divide the watts by the voltage to come up with the number of amps.  Once you have a total number of amps per hour used by everything you can see how many "amp hours" your batterys have and know how long you can boondock and not recharge.  Keep in mind batteries suffer greatly if discharged more then 50%.


  John and Tim are right on the ball here also. 


   We live on a sailboat and travel/boondock a bit in our old Cabana.  We have a wind generator and a 120 watt  solar panel.  Most lights are "LED" huge power savings!  Spendy to buy but worth every penny.  In the marina where we live if you do not use 20 dollars worth of power each month you get no bill.  In two and a half years now we have not had a power bill.


   Hope this helps, Tony, Joy and Cool Paw Luke

Whew, you guys are great! Thank you so much for your input. We are starting our adventure fairly late in life, 65 and 70, and we very much appreciate all the help we have gotten from old RVers.

Many Blessings, Maryann and Edward.





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