Adding solar panel

We have 2 140 watt panels and a 2800 watt inverter....with 6 golf cart batteries. We run all that you talk about on the batteries....with exception of the tv. DH does not want to trust running the tv on batteries...he's afraid he'll have to hear me snore during the night if the batteries die. As others said, camping under trees does not work for getting sun power.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet by N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

For such a tiny battery bank I'd recommend about 270 watts.

The 100watt may be a little small for your needs. I would go with a 160 or 200watt panel. You can always add panels later. Make sure you get a controller that can handle the watts you decide to buy. Also when you buy new batteries get 2 RV deep cycle batteries.
I would not want to be without my 120watt panel. I can go for days without needing to run the genny. I only run the genny when I need A/C or run the microwave.

100 watts might be a bit light depending on use. You can add more later if needed so good to go.

Is that a local panel to save shipping or do you want to compare prices?

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.

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?

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.