No, the 9w panel will do next to nothing. Best case is you'll squeeze out 40w/h of energy from that panel (9w * 75% efficiency * 6 hours useful sunlight)

it all adds up, I encourage you to sit down and do the math. Better still, mock the system up in the back yard, and grab a multi-meter and check for yourself.

FYI, and inverter is typically only 75-85% efficient, which means if you have a 50w load, to the battery it appears to be a 75W load. Incandescent rope lights are horrible at 900w per 150ft, LED rope lights are awesome, only 120w per 150ft. But run that LED rope through an inverter and it suddenly is using 150w. If you're running them for 10hrs, that's 1500w/h just for the rope.

Detailed calculations are provided in another thread.

> EESH!! I need 200 watts of solar?! That seems excessive to me. You guys aren't messin with me are you?

You may need more. In my experience, I think they are being optimistic about the 75% efficiency. You *might* get that if you kept you panel facing directly toward the sun all day, and kept the dust off the surface. Solar can be difficult, especially in BRC, as the panels are very valuable and usually must be hidden to avoid thieves. That makes them hard to keep focused and clean when they're laying flat on the top of your RV/trailer.

One thing I've done is have two pumps in my RV. One is a 30 PSI and the other a 45 PSI. When I'm trying to conserve battery power (or water/waste tank), I switch on the lower pressure pump.

Also, if you have a propane fridge, it will require some amount of power to monitor the temperature and operate the gas valve. Running out of 12V would be a problem.

The math is pretty straight forward, calculate watts times hours for demand. Then calculate the panel and charging in watts * hours times 50% efficiency (usually best case, often worse). You need more charging than demand or it won't work well. If you buy an inexpensive watt miser, they can tell you exactly how much each of your appliances is using. Also, a good charger will tell how much current is going into charging. With those numbers, you can calculate fairly closely. Otherwise, we're talking in broad numbers like you see here.

Watts is Voltage x Amperes. Watt Hours is Watts x Hours.

So, a 12V appliance that needs 3 amps and runs 10 hours a day will require 12x3x10=360 Watt Hours (WH), or in terms of battery consumption it requires 3x10 Amp Hours, or 30 AH. You can see how a small load can easily consume almost half your battery's capacity in a short amount of time.

To convert Watts into Amps, divide the watts by the voltage. So a 50W load will require 50W/12V=4.17 Amps. You can then multiply that by the number of hours to get Amp Hours.

You can efficiently use about 1/2 of your battery's rated 115 Amp Hours, or about 60 Amp Hours before you must recharge.