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how much solar?


Tex Bigfoot

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Packing the roof is great but keep in mind he wants a ground mount system that he can put out and store inside. Going to need a few small panels or he'll end up with shattered glass at the first handling oopsie.

 

For a roof mount system today I'd load it up too, back when it was $5.00 plus per watt the cost was a killer but today it is the way to go.

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You cannot have too much power . . .

 

Most def, but you can certainly have too little.

 

For example, our RV is in an open-air AZ storage facility. I figured my 3, 245W panels were more than enough in the AZ sun, so I left my inverter on to supply mostly parasitic loads (microwave LEDs, etc) and I also turned my AGS (Auto Gen Start) off.

 

However, several cloudy days drained my batteries, so I leave the AGS on now.

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Jack

 

You have enough space on a 45' RV to run at least one a/c and perhaps two when the sun is out.

 

Googled the 305 W panels you have and they are the same width as our 235s, about one m. Yours are about 1.6 m long and I can see why you placed them as you did. It gives you 1.5' to walk the top of your rig.

 

As you noted, the costs of panels has dropped so much that they are the least expensive part of the equation. Our older son is a solar contractor and buys panels by the multiple pallet load. I think he has 4 or 5 pallets waiting for his projects at his place in the mountains of northern New Mexico. Was just there and it was cold. Got back to visit daughter in Las Cruces, and it should be mid-50s the rest of the week. It was 18 below at younger son's place in Colorado - where we found out that diesel can gel without additives. So much to learn and so little time

 

Do you have your panels in parallel or in series. There is a long run from the roof to controller so that higher voltage has its advantages.

 

Reed and Elaine

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Reed, my four panels are in parallel. But the voltage is high enough, and the wire large enough that it is fine. I stayed off of the series because of shading issues. But I could have done series/parallel. It is all a judgement call. As you know.

 

I chose that size panel to be sure I had walk space.....as you noted.

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Jack

 

Have seen photos of RV rooftops that are totally covered with panels. The only way to get to them to clean/scrape snow etc is by ladder. Well, maybe that is not a bad idea. Tried to get up once with wet snow and I could not even sit down without sliding and opened the telescoping ladder. Even with 6" of snow, we were still harvesting 100 W. Removed the snow and we were up to 300 W.

 

Our 235 W panels are 30 V so I would guess that 305s are about 39 V which assuredly is more effective power transmission than 12 V. Son has gone to 250 W which are made in USA.

 

Our panels our ganged in two sets of 3. Three nearest the rear are one set and those nearest the front are the other set. We have had times when only one set was in the sun and our power was down around 650 W at mid-day and that was enough since we did not have to use the air conditioning at those locations. Have camped in full tree shadow twice for a week(Cave Creek in the Chiricahuas and then near Olympic National Park). We were only getting about 300 W-hr total in 200' rain forest trees. The battery bank lasted nicely both times with no problems but we turned off inverter when not needed for m/c and TV (for our DVDs of BBC Mystery Theater)

Reed and Elaine

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  • 4 weeks later...

I've got more questions for the ones that should know.

 

The nice kit that I bought (as usual ) was not in my opinion not a complete kit. it only had about 3 feet of wire .

So tell me if I'm out in left field here with these thoughts.

The wire in the kit looks to be 8 gage aluminum ,that being known I have an old 10 gage copper extension cord that I am willing to sacrifice the copper in my mind will conduct better than the aluminum so the resistance should be about the same . IS THIS RIGHT ?

 

I don't look at running wire more than 30 -35 feet between the panel and the controller then only about 2-3 feet to the battery. DOES THIS SOUND OK?

My thoughts with the old cord is that it will make set up a lot easier by not having wires that will not tangle up so easy and can be connected with wire nuts on the panel end and still small enough that it will fit the lugs on the controller.

 

Glad that hunting season is over so I have time to get this set up.

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Without knowing what the panels are and their specs it is hard to respond.

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

PLEASE no PM's. Email me. jackdanmayer AT gmail
2016 DRV Houston 44' 5er (we still have it)
2022 New Horizons 43' 5er
2016 Itasca 27N 28' motorhome 
2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU
No truck at the moment - we use one of our demo units
2016 smart Passion, piggyback on the truck
-------------------------------------------------------------------------
See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar power
www.jackdanmayer.com
Principal in RVH Lifestyles. RVH-Lifestyles.com

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Are you just planning on topping off your single battery with very little use? Perhaps if you made note of the system you bought it would help to answer your question. Enjoy your system and the use of solar.

 

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I would not use aluminum wire... and I would choose #8 wire not #10 for a run of 35 feet. On a cold morning with full sun your 100-watt panel could easily hit 8 amps.

 

Use wire rated for outdoor (UV) use.

 

If you just do stuff like use the lights at night and listen to the radio that 100watt panel will do ok.

 

WDR

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We used two 35-watt panels leaning against the tow hitch of our 1970 21' Streamline travel trailer for a long time. As long as we had sun, we had enough power to charge one laptop and keep at least one light going. But a cloudy day will fog up your results. :D

 

In 2010, at the CA state park at Dana Point (where there are zero hookups but at least a beach) we had many people ask us "do those things work?". I resisted the urge to be sarcastic because I could hear the generators from the big rigs in the $60/day slots across from us running 24/7.

 

Luckily, the morning after a pickup truck and camper settled in beside us and started up their 2000 watt generator and ran it 'til midnight we were due to leave anyway. At 7am I had my diesel pickup warming up and took my time hooking up with no effort to keep the noise down. LOL

 

WDR

1993 Foretravel U225 with Pacbrake and 5.9 Cummins with Banks

1999 Jeep Wrangler, 4" lift and 33" tires

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Probably sound like a broken record but with the cost of panels going down by an order of magnitude in the last 10 years, there is not reason to skimp on buying panels. The cost is then controller and battery bank if using only DC, and an inverter if planning to use AC.

 

If you have system installed by an RV shop, you will pay way to much. There are a number of reputable on-line folks that will ship simple and effective systems that most folks can put together.

 

Reed and elaine

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