How many solar watts should I get?

Solar Blvd is selling a 75 watt panel for $93.75 plus shipping and tax (link). This panel weighs 15 lbs. which would make it easy to handle and store.

To start with, I would advise buying two 75W panels and no controller. When I helped a fellow camper hook up his panel I used a standard 3 wire 50ft. 12 gauge extension cord. I then chopped a short cord in half and wired the female end to his battery and the male end to the panel. Since only two wires are needed you can tie the green and white wires together which gives you less resistance and thus less voltage drop. Connect black to positive and green/white to negative.

If you monitor your battery condition closely you can get by without a controller. Also it would be a good idea to unplug the panels at night to prevent possible discharge through the panels. Some panels have diodes to prevent this.

If this works well you then can think about a controller. The cheapest approach is a PWM controller. The most efficient and more costly would be the MPPT controller. With two panels you could connect them in series which would give you a nominal 24 volts (closer to 40 volt actual). This gives you less voltage drop between panels and controller. The MPPT controller knocks 24 volt down to the proper charging voltage.

I have a very simple 135 watt panel with 2 12v batteries. I switched out the lights I use the most for leds. I never have to start my gen unless I want to use the microwave or the DW needs her blow dryer. Keep it simple!

Katoon;
Using the web site link, you an do the calculations as to determine, how much solar and batteries you will need. See my signature. My system cost me less then $2000 over a 2 year period. First panels were 180w @ $300. My last panel 280W cost $200.

Solar Tools

good luck

Some propane detectors are hogs and some are very thrifty. Depends on the model as far as I can tell. Mine is thrifty.

Now we're getting some good info. :B I appreciate everyone's input. You guys are great.

And Almot, thank you. I did get that spreadsheet to load up. LOTS of info too.

Golden_HVAC wrote:
Hi,

I did not read what everyone else wrote.



Fred.

Well surely you read the OP by the original poster.
So what part of "portable" didn't you understand ?

How many? Most of the posts I read say, ("I started small and added")
The same is true here. I'm using one of the $12.00 PWM
controllers from EBay that has brought my batts up to the same level as my 120v charger. Yes, it's true.


O&S
Floyd

Why would anybody use a solar - oh please, can we not go there on this forum at least :) ... I saw all kinds of campers, with varying levels of knowledge. Spending $2000 on solar doesn't mean getting it right, (not to mention MUCH higher prices few years ago), and yes, some have louder generators than others. A/C is difficult to run off the solar or off battery, there is no question about it.

Katoom, the spread sheet calculator in my link works. You need to have MS Office in your PC. Click on the first link that is not a zip. Then click "Open with" -> MS Excel default. Then fill the values in spread sheet and see the results, click on the bottom tabs "RV load calculator" or "solar array size".

Hi,

I did not read what everyone else wrote.

I have a "E-Meter" that carefully measures the amperage going in and out of my battery bank. It shows I use about 0.8 amps when the refrigerator is not calling for cooling, and 1.2 amp when it is cooling. So basically the RV will consume 35 AH dialy just to run the CO and propane detectors and refrigerator.

That is about what one 7.5 amp 120 watt solar panel will put out on a sunny day. So start with a minimum of 120 watts and go up to 300 - 350 watts if you want that much.

I would stick with smaller panels, say 100 to 185 watts, anything larger and you will find it difficult to locate them on the roof, and still be able to walk past them to do maintenance.

SunElec.com sells some panels for less than $1.50 per ratedwatt. If you see something on the web page that says $1.22 per watt - 4 panel minimum, call them and ask for the single or 2 panel price.

You would also need a controller and wiring.

I used #10 wire - UV rated direct burieal wire from Home Depot. I ran the wire down the back of the refrigerator. Then to the controller, then those wires to the battery.

Fred.

Its very simple
Buy a 100 watt panel ($140)
Buy a 20 amp controller, incase you want another panel later ($15-$20 max)
Buy the 10 ga x 25 ft cable to connect it ($20-30)

Less than $200 total.
If you find you'd like more, buy another 100 watt panel ($140)

Its what I did. And I am thrilled w/ 200 watts.

Don't buy 50 watts, unless you need a battery maintainer some where.

I just loved the post that said, "mount'm on the roof, and park in the sun"
It must be nice to have friends like that !