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Old 05-22-2016, 11:15 AM   #1
evy
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Planning solar pannels

Hi everyone,

I'm working on my very first DIY camper conversion, using a 2010 extended Ford E250.

I was looking at solar panels yesterday, I was going to make the move eventually but maybe sooner than I originally thought.

I just want to plan where the panels will be mounted on my roof rack and how many I needed, this is what I came up with.

I can fit a big 285W solar panel on the side of my van, with hinges on top and some sort of an adjustable bracket (see drawing)

I can also fit two smaller panels on the top of the roof rack but only in a specific area, I need space for my canoe or kayak on the right side and I can't put them too close to the rear which is the highest point of my van, as of now I have 2-3 inches of space when I back up through my garage door...

There probably is a 100W thin model I could install, around 20"x48" ish ?

Take a look at my roof rack drawing, I added the panels (clouds)

Also Is 485W of solar energy worth it? I don't know much about solar, I'll have two 6v golf cart batteries at 225AH.
My rig is fully equipped, 3 way fridge, microwave + convection, LED lights, pump, fans, AC + DC outlets...

I red that you can get more energy out of your panels by tilting them to face the sun.
Does anything exist on the market today to manually adjust the angle of a panel, I was thinking of adding a sturdy central bracket.

Thanks for any help!


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Old 05-22-2016, 11:40 AM   #2
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If you search the forum for "solar" you will find plenty of info. As for adding a way to tilt, here is one some good info on why you want to do that.

http://www.sportsmobileforum.com/for...ers-16955.html

I'd recomend adding as many watts as you can due to your loads. The fridge will use up quite a bit of your capacity to begin with, and even 30 seconds of microwave use will probably tax your batterys beyond the desired 50% discharge point. Solar panels in general are way over rated in terms of output. My 3-100w panels put out just over 50w under ideal conditions. It seems they only make 100w's in the lab, and this is pretty universal due to the way the marketing departments rate them. So, again I'd recomend installing as many watts as possible if you want to avoid running your engine every day. If you want a better explination of why you don't get the rated output, scroll down to post 15 in the below thread.

http://www.sportsmobileforum.com/for...ket-16568.html
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Old 05-22-2016, 04:32 PM   #3
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evy - lots of factors to consider in your solar. Do research first on mixing panels of different watts and voltages, as well as series/parallel connections. If you are mounting panels here and there than multiple smaller panels of the same size are the way to go. There significant penalties for mismatching. Second re: tilting, there are some well done studies at various latitudes/ time of year about the benefits of tilting. The more southerly (in the northern hemisphere) one goes, the less beneficial. You may be far enough north that it may yield benefit. Next, your loads - do a calc of what your draws will be overnight and during the day. The size of your panel and battery bank will need to accommodate overnight drawdown so by morning there is at least 70% of your bank capacity is left. Then figure your draw during sunlight hours plus an allowance to replinish what was drawn overnight. Minimally, your battery bank should get you through 60 hours of no charge and not go below 50%, in case it is raining. Day three of rain you start the engine.
Not a fan of a side mounted solar panel on hinges idea, but probably due to esthetics and inconvenience. Windage and awning interference would be another important consideration.
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Old 05-22-2016, 04:40 PM   #4
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Quote:
Originally Posted by arctictraveller View Post
My 3-100w panels put out just over 50w under ideal conditions. It seems they only make 100w's in the lab, and this is pretty universal due to the way the marketing departments rate them.
AT - I think something is wrong in the setup of your system.

My 300 watt panel has seen 292 watt arriving at the controller on a great day. Pretty much can count on high 190 area even on overcast day. You should be seeing similar numbers if your panels are clean, not shaded. Are your panels in series of parallel? Is your Solar controller rated to receive the volts/ amps coming in from the panel? Thxs! Ray
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Old 05-22-2016, 04:52 PM   #5
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I'm running 270w worth of solar that charges two 4-D batteries which total 420AH. That works fine for my needs. On a good sunny day I might average about 12-14A worth of charging. Most of my friends are fine with a 130 panel and a single 4-D. Just depends on what you use as an average daytime load including the time required to recharge the batteries. YMMV but most of the stuff I run is either low amp (about 2-5 amps) or higher amp items like the microwave which pulls about 70 amps. There isn't enough room on the roof for the number of panels needed to directly power the microwave off solar so you need to factor in how long it takes to replenish the battery after its use. In most cases more solar means you get a better charge rate in medium overcast skies. It also means faster battery charge times. Nightly (always on) loads I use are the fridge and Espar heater or a fan in warm weather. I usually use a couple LED lights and maybe watch a DVD for a few hours. By morning I'm down about to 70% DOD unless I have ran the microwave for a couple of minutes on low after dark. My AGM batteries are usually fully charged by 11AM (if not sooner). Because solar doesn't work great in overcast you'll have to factor in how much solar you'll need to at least power the fridge on those hazy days. The problem is how much overcast affects the output. It sure isn't linear. Heavy overcast makes even the largest solar system you can get on the roof is practically useless and might require running the engine or a generator to supplement the charge. I'm not saying I wouldn't want more solar but in my case the area for a storage pod out weighs the need for what I would actually gain in performance by adding more panels. There is also a cost factor.

Here is a good article about RV load.
RV Electrical Power for Dry Camping
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Old 05-22-2016, 05:19 PM   #6
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A very easy way to run your microwave without killing your batteries is to just crank the van. I do this every time. Your alternator will juice the inverter enough to where your bank only drops a half volt or and it's quickly recovered if you let the van run about 30 seconds after you're through using it. This may be a little bit of a noise nuisance depending on your campsite or how loud your (diesel) van is but much quieter than running a generator.

Also, AT, I agree that something isn't right with your setup. I added a 2nd 100 watt panel or Slacker, who just bought my van, and I was seeing 10-15 amps coming in during the sunny part of the day.

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Old 05-22-2016, 05:34 PM   #7
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Evy, welcome to the fun world of solar. I realize you may be feeling overwhelmed with all the info your getting but I'm going to add one more thing to consider. Voltage Loss is one of the biggest issues with poor performing solar systems. (AT I also agree something might be under performing in your setup). Limit voltage loss where ever you can. Use large wire, place your charge controller close to your batteries, buy a controller that has sense leads to the battery and temperature compensation. I would recommend going one wire size larger than whatever voltage loss calculator your using for the design. You get the idea that I'm kind of big on voltage loss but a solar system is expensive and skimping on wire producing a poor performing system is even more expensive. I have seen very well designed small systems out perform (i.e. produce more usable energy) than larger systems. Adding solar to my van is maybe the best addition I've done.

If I can be of assistance please ask.
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Old 05-25-2016, 10:53 AM   #8
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Originally Posted by 1der View Post
AT - I think something is wrong in the setup of your system.
I agree. My current setup uses the supplied connectors, and wire (8ga as best I can remember) an MPPT controller and remote monitor all from Renogy with the panels connected in series for less loss. From the panels to the batterys is about 8 feet (16ft round trip) so there is not a lot of loss due to voltage drop in the wire, although bigger wire is always better (to a point). It's possible I'm getting inaccurate info from the remote display though, and plan to upgrade to a quality one like the Link 10 pro. Meanwhile, I can only look at the panel output on the remote display and as I said, I've never seen anything close to 300W. In the link I posted in my original reply, Scalf77 posted a very complete explination of why panels rarely make the rated wattage here http://www.sportsmobileforum.com/for...ket-16568.html.

He sum's it up with this paragraph:

"Looking at the 140 Watt panel under NOCT we are getting out about 101 Watts or Vmp of 16.00 Volts and an Imp of 6.33 amps, the best that we can do with a PWM controller 6.33 amps X Battery set point voltage 13.5 Volts. Disregarding any loss for conversion this would yield us about 85 watts (6.33 X 13.5). So now in reality your 140 Watt Panel is really yielding you 85 Watts."

This is a very close percentage loss to what I'm seeing from mine. Still, if folks are reporting much better results, hopefully there is room for improvement, but I do wonder how they are measuring panel output. I imagine there could be a difference between different manufacturers too. This fall I will double check my wire sizes and connections, and install a proper amp monitor. Hopefully I'll record some better results more in line with what other people are reporting.

EDIT: I just noticed Ray reported measuring his panel output at the input side of his controller, where as I'm reading the amps output from the MPPT controller which includes the losses from the controller, which is inline with the calculations above.
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Old 05-25-2016, 02:00 PM   #9
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My typical output readings are about 12-14 Amps if the batteries are low and the panels are in a good position. On the best days I've seen +/- 15 on a 270 watt system but that doesn't happen much. Seems to be close to Greg's calculations.
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Old 05-25-2016, 03:12 PM   #10
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I hope I'm staying near evy's original topic of what can be expected from a solar system, wattage, tilting, ect. Just wanted to share what performance I've been seeing with my configuration which is fairly small.

Panels are 2 140w - Kyocera KD140SX-UFBS which I think are kinda traditional and not revolutionary technology. They are wired in parallel and do not tilt, tilting is good I just chose not to.

Controller is a Morningstar Tristar 30amp MPPT - is kind of a beast for this small of a system but the Tristars are, well, bomb proof. And I can program/modify the charge algorithm. I am using the voltage sense leads to the battery and temperature compensation.

Battery monitor is Bogart Engineering TM-2030 - simple and reliable.
monitor shunt is located 12" away from battery on neg 2/0 ground cable.

Wire is 12awg panel to Jbox on roof, 8awg Jbox to controller 10' one way run, 6awg contoller to main buss 6' one way run. 30amp fuse pre-controller, 40 amp fuse at main buss.

So here is the performance as of 11:00 am this morning in my driveway.


Some of the factors to think about. It is May 25 and 11am so the sun is pretty vertical. It was clear sky with a hint of high cloud. Air temp 70*.
I ran the electric water heater prior the photos to drop the capacity of the battery enough so it would accept the full wattage from the cells AKA constant current mode or MPPT mode, etc). I had everything off in the van however there is always a .3amp draw at all times on the house system, clocks, sensors.

As far as minimum and maximum days when its raining I'll only make 30 watts, overcast 70 ish, but if its cold 45* panel cold I've seen 310 watts for a few minutes until the panels warmed up and then they might settle to 280 watts. However 220 to 260 is the normal unless it's 95* air temp and panels are, I don't even know how hot, lava hot, then maybe down to 190 watts. It's very temperature dependent.

So I hope this helps folks in some way with solar projects as to what one system produces. If I can be of assistance please ask.
-Eric
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