Adding solar panel

[wademartin]

I have a 5th wheel camper with two Exide Stowaway Group 27 Marine/RV batteries wired parallel that powers my 12 volt panel and connected to a 300 watt inverter that powers my CPAP machine, my satellite receiver, flat screen TV, electric razor and cell phone charger when off shore power. To maintain my batteries I proposed to add a 100 Watt Polycrystalline Solar from Grape Solar on the camper roof with a Sunforce 10 Amp Digital Charge Controller. Any comments, suggestions or advise will be appreciated.
Thanks, Wade

[Golden_HVAC]

Hi,

I installed a solar system on a fifth wheel for a CPAP owner. He still needed to run his generator some times due to the batteries going dead. The CPAP used a lot of power.

I installed 4 each 100 watt solar panels. I think he had 4 batteries.

400 watts is a good place to start. I had a 400 watt system on my motorhome, and 4 golf cart batteries. I also installed a 'e-meter' and it accurately measure the amperage going into and out of the batteries. I could use 120 amp hours in one night, and expect the system to fully charge the batteries by 6 pm.

My RV uses 35 amp hours daily just to run the refrigerator, CO and propane detectors. Any lights, computers, and other loads will increase the amps that you need in the batteries. I used a lot of TV and ran my satellite dish a lot. Now that I have a CPAP, I will need to expand the solar system, or run the generator a lot to make the power that I will require. I figure that I will need about 600 watts and still OK with 4 batteries.

SunElec.com has solar panels close to $1 per rated watt. Look for 12 volt nominal panels, that actually are rated at 21 volts with no load. The "Short circuit" rating is often called it's output - however it will never put that out, except when there is no voltage, in a lab.

I figure that my 120 watt solar panels put out about 7 amps per hour (at noon) and will put back about 35 amp hours daily. Take the 'rated' amps X 5 hours, and you will get a average amp output per day. You will get less in the trees, in the winter, and on very hot days. You will get slightly more on a longer summer day (except that heat prevents full amperage output) and when at a higher altitude.

Good luck!

Fred.

[ewarnerusa]

Go for 200 watts and upsize the controller to 15+ A capacity. If you're mounting flat and fixed, make efforts to park on the sun. Can the CPAP be run off of 12V?

[Veebyes]

How good the solar works for you will be dependent on your style of camping. If you like camping in the trees then the solar panel won't be of much use. A small genny will be money better spent. If you like being out in the open then the solar will give quiet help to keep the batterys up depending on what you have on & amount of sun. Solar is not going to equal what you charger can do with the genny.

Also, when it is time to replace those group 27s look into getting group 31s, same or close case size, or a single 4D.