Solar for beginners - Fiberglass RV


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Old 04-15-2015, 12:24 AM   #1
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Name: Aimee
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Solar for beginners

So, we really want to do mostly solar with a small 1000w gas generator as backup. What kind of system would those with more expertise recommend? I could research inverters, panels, batteries all day, but at the end of the day I want to know what works for everyone else. What's a good, reliable, simple setup? We are planning on building a fold up (cheap) wood holder for the panels so we can keep them into the back of the truck camper when traveling. Let me know what brands you recommend and what parts I will need to hook it up. I've done research...but all the options get so overwhelming. Thanks!
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Old 04-15-2015, 02:21 AM   #2
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We lived aboard a sailboat for 2 years in Mexico and relied on solar for about 90% of our electrical needs. That included refrigeration (electric compressor type), lights, computers, fans etc. To design a solar system, first you need to estimate your daily consumption, in amp hours. An appliance that draws one amp will use one amp hour for each hour of use. Then figure out what sort of battery bank you can manage. The bigger the better. If you can deal with the weight and bulk 2 6 volt golf cart batteries in series is about 230 amp hours total. Bear in mind that deep cycle batteries should not be discharged below 50% of their capacity so those 230 hour batteries really only provides 115 amp hours before they should be recharged. Finally, determine a realistic rate of recharge with the panel array you plan to use. Remember, solar panels only work in direct light; partial shade will rapidly degrade their performance. And they don't work well in the early or late parts of the day. So in a short winter day of 10 hours, you might get only 3-5 hours of peak generation. And your panels must be correctly oriented to get maximum output.

To monitor your battery bank, a battery monitor is a nice addition but you can get by with a good voltmeter and a hydrometer. And you will want a charge controller to avoid overcharging your batteries too. For recharging from the generator, get a good quality smart charger that has multiple phases of bulk, absorption and float charge.

In any solar system, it is always better to find ways to cut consumption. So replace those inefficient incandescent lights with LED. If you have a 3 way fridge, you can forget about running it on 12 volts; way too much power is used by absorption type fridges. The 12 volt compressor units are way better if you want to use electricity for refrigeration. And you can forget about air conditioning too. Small 12 volt fans will have to suffice. Whew, that was a lot to absorb in one post?
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Old 04-15-2015, 07:02 AM   #3
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Good write up from David. I'd just add that I like the permanently mounted panel or panels over a portable, no storage or setup. While I'm finding a single 160W works well under good conditions, for those rainy overcast weather or winter sun, leaving an easy upgrade path for adding a 2nd panel would be a prudent step to take during the initial install. Amounts to running heavier cables and getting a big enough controller. I'm taking it for granted that your Bigfoot has room for 2 batteries.

Having the 1000w generator along gives you the option of running it an hour or two in the am and letting the solar top off the batteries for the rest of the day. Depends on your style of camping.
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Old 04-15-2015, 07:19 AM   #4
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David, that is super amazingly helpful. Thank you so much for all the wonderful information. And Bob & Deb, I've heard running the generator a little and then letting solar do it's thing is a good way to go. Great advice. Although, I think the only way I might put solar panels on the RV is with the super thin flexible ones. I've heard of others attaching them to the truck camper shell. My husband just wants to be able to move them to get better sun if needed. He's really into building the fold-able stand for them
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Old 04-15-2015, 08:27 AM   #5
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Name: John Michael
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Aimee,

If your dh wants to hassle with set up and orientation portable panels are the way to go. The only downside is risk of theft if unattended. Being basically lazy when camping I just opted for roof mounting and choose a bigger panel (100 watt) to make up for less than optimum orientation. It provides all the power I can use on sunny sites, and does pretty good in partial shade. My battery will go for 3 or more days with no charging so full sun isn't necessary each day.

John
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Old 04-15-2015, 08:30 AM   #6
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I agree with your husband. When/if I get a solar panel, it would have to be movable by me independently to find a sunny spot, and ideally it would automatically track the Sun. Panels fixed to the roof of the camper only make sense in the desert southwest - few trees, few clouds.
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Old 04-15-2015, 08:39 AM   #7
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Name: Aimee
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Quote:
Originally Posted by Paul O. View Post
I agree with your husband. When/if I get a solar panel, it would have to be movable by me independently to find a sunny spot, and ideally it would automatically track the Sun. Panels fixed to the roof of the camper only make sense in the desert southwest - few trees, few clouds.
Totally Paul...same boat here. I don't want to "have" to park in direct sun. It seems the trailer would heat up a lot faster without some shade
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Old 04-15-2015, 09:58 AM   #8
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Quote:
Originally Posted by HarryHendersons View Post
David, that is super amazingly helpful. Thank you so much for all the wonderful information. And Bob & Deb, I've heard running the generator a little and then letting solar do it's thing is a good way to go. Great advice. Although, I think the only way I might put solar panels on the RV is with the super thin flexible ones. I've heard of others attaching them to the truck camper shell. My husband just wants to be able to move them to get better sun if needed. He's really into building the fold-able stand for them
Flexible panels tend to put out less amps per square foot, at least the ones I own do. And they usually cost more and are less durable. I also found out that combining flex panels and hard panels did not work very well; the flex panels had slightly lower Voc (voltage open circuit) and just did not put out the amps in a combined array. If the lighter weight and easier storage are paramount, then go ahead with the flex panels. But I would choose hard panels otherwise. I should add one caveat; most of my solar experience is based on about 8 years ago and technology has changed since. Also, if you put the panels on the RV, you will have to park in the sun. Even a bit of shade will dramatically reduce output.
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Old 04-15-2015, 10:31 AM   #9
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Note there are now "sorta" flexible panels that can be bent in an arc as they are mounted on thin flexible plastic. They cost a little more that the "regular" glass panel ones but are much lighter (IIRC, 3# vs 20# for a 100w size). They have the same kind of silicon and put out the same power as the glass ones. The real flexible kind you can roll up but they produce significantly less power per sq ft then the other kind.

We found, even in Florida, in the winter, aiming the panel at the sun gives a lot more power.

Our 100w panel, Xantrex controller system puts out a maximum of about 65watts to the battery. The controller has to throttle back the solar panel voltage to charge the battery properly. In my research I wasn't convinced a more expensive MPPT controller would have actually done any better.


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Old 04-15-2015, 11:24 AM   #10
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On my Scamp 13 I use 2 -30 watt aluminium framed monocrystalline panels bought on E-Bay and a cheap controller also bought on E-bay. I made sure the controller was rated twice what I needed. I have one group 27 battery and all my lights in the trailer have been changed to Led's I have even run my trailer heater all night which consumes the most power in the short time span. Out west here we have an abundance of sunshine. All of our campgrounds have an abundance of sunlight. Camping in an established campground with a shady spot all day only applies to the lucky few, most will have to bear a fair amount of sun.

Here my limited solar takes care of all my needs and then some. I arrive at the campsite and I put my portable panels on the roof through the emergency hatch and plug it in through a high amp trolling motor plug to the controller. The charge will usually fully recharge my battery by noon or so from a 12.4 overnight low on the battery.

It would be nice to have a small generator to provide the 110 power for limited use but so far we have gotten buy without it.

Think about where you camp and how much sunlight exposure you think you will really have and size your system accordingly.
Just make sure your controller has extra capacity so if you desire to add extra or larger panels you don't have to redo everything.
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Old 04-15-2015, 11:49 AM   #11
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Name: Diarmuid
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Thank you all for all this Solar information....especially David.....This small brain of mine is now a lot smarter than it was an hour ago.....
MrInver
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Old 04-15-2015, 12:14 PM   #12
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Another thing you'll want to add are some small inverters so can charge your laptop, run a small blender and other small appliances with out firing up the genny. A microwave is usually not a good idea; too many amps and I think they are fussy about the type of inverter. Even the cheapo inverters that put out a square wave AC (instead of the proper sine wave) will work for most of these uses. I would stick to about 300 to 500 watts max unless you have a BIG battery bank. Even a small 500 watt inverter can pull over 40 amps from your battery bank; Yikes!
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Old 04-15-2015, 12:22 PM   #13
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A general rule of thumb is you get half the daylight hours at 50% output and half the daylight hours at close to 100%. Can generally use 4 hrs. @ 50% and 4 @ 100% to calculate how many amps that panel will put back into the battery during the three seasons. You get a bit more than 8 hrs. but at low output and you generally don't hit 100% so it all works out as a guide.

You have to balance usage against panel amps provided to determine if you can replace all your usage in the battery, and if not how many days you can tolerate a deficit in panel production from rain or clouds and still stay at 50% of charge on battery. Batteries deteriorate if discharged below 50% charge.

Make a list of items that draw power.
  • Lights
  • Water Pump
  • Fans
  • Furnace blower (if cold enough weather)
  • Charging/running technology gizmos (camera, laptop etc.)
  • TV
  • Satellite dish
  • Stereo
  • Refrigeration (if applicable, as noted before not for 3 way)
  • Any appliances such as coffee pot, blow dryer etc.
  • Health equipment such as CPAP or Oxygen generators.
Second step figure out how many hours you use said devices per day.
  • Lights x hrs.
  • Water pump x hrs.
  • Fans x hrs.
  • etc.
This stuff is very individual take lights how much you use lights depends on if you stay up late reading or playing cards or hit the sack shortly after you come in. Or get up before full daylight.

Have a shower? Shower every other day or shower daily while camping? Then you will run the water pump more or less than someone else.

We don't even take a TV or have a stereo, many do. We might use the laptop more than most for photo editing, video or music.

At the end of this step you will have a list of how many hours YOU use what devices.

Then look at the device and find its amp usage to add to your list.
  • Lights x hrs. times my bulb amps = ?
  • Water pump x hrs. times my pump amps = ?
  • Fans x hrs. times my fan amps = ?
  • etc.
At the end of all this you can add up exactly how many amps you personally expect to use in a day. Every appliance will have it's power draw listed on it someplace. That is how you know how many amps it draws. You already figured out how many hours it will be running.

Incandescent light bulbs might use 1.9 amps while LED bulb might draw less than a hundred milli amps. You might have an energy efficient fan in the vent or be running a higher draw fan on the counter for a breeze.

The panels are generally listed as being so many "watts" but what you want to know is how many AMPS does it produce. The panel in its description should state how many amps it produces. A 100 watt panel might say it produces 5.2 Amps.

That you can plug into the rule of thumb to be:
4 hrs. producing 1/2 output. 4 @ 2.6 (.5 x 5.2 amps) = 10.4 amp hours
4 hrs. producing full output 4 @ 5.2 amps = 20.8 amp hours

So you can replace a total of 31.2 amps of use from your personal list of power usage per day. If your battery is a 100 amp hr. battery then you can use 50 amp hrs. without charging or draining the battery too low.

I would use very little with 2 LED lights, no water pump, might run a fan. laptop plus some phone & camera charging so might only use 10 amp hours a day. I could go 5 days just on battery and if I got even one sunny day that put 31.2 amp hours back in that would add 3 more days I could run.

Folks with a shower, furnace and who watch TV for a few hours each night would find my "perfect" solar panel and battery left them with a dead battery after one day of rain.

I think a lot of people may be over powered. Better safe than sorry I guess but it is only by calculations based on your power use that you can figure out what you need the solar panel to replace, and how much battery storage you require to allow for some rainy days.
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Old 04-22-2015, 10:57 PM   #14
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We just bought a Bigfoot camper and want to install a solar panel on the roof. I have heard that 3M VHB tape can be used to hold the panel to the roof, but I think I would like something that screws the panel to the roof. What do you folks use to secure the panel to the roof?

Thanks
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