Playing with Solar - Fiberglass RV


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Old 10-05-2014, 08:22 AM   #1
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Playing with Solar

It was an insanely beautiful day here yesterday so I decided it was time to get my solar toys from Renogy out and see what they would do. I do not have my new dual 6V batteries yet, they are next months purchase, so I just used my knock around tractor battery for the experiment. I hooked up one (100W) panel at a time to the charge controller and remote meter. It was fun watching the MPPT controller doing its thing charging the battery with a range of 16.something volts to low 17.something volts. I had the three panels lined up on the back wall of the porch pretty vertical but facing South at around 1PM in the afternoon. It was ideal conditions for solar charging, cool and sunny. Interestingly, the voltage jumped 1 volt just by laying one down at a more correct angle. Imagine that, angle does matter.

So far this is what I have spent (going from memory):
$270, "Kit" with 20A MPPT Controller, 100W panel, mounting clips (that I probably will not use) and 20 feet of (too small) 12 Gauge wire with MC4 connectors.

$129 each ($258) for two additional 100W panels.

$35 Remote Meter

$13 MC4 "Y" connector

$7 MC4 connector tool (not required but well worth it IMHO)

$15 (I think) for 10 MC4 connectors

$20 Misc. fuses and fuse holders

I still need some aluminum angle and stainless hardware to make my roof mounts and a weatherproof cable entry port for the roof, along with various wire bits (some of which I may already have). I don't know what all that adds up to, and don't want to know right now.
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Old 10-07-2014, 06:22 PM   #2
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So how has it gone? Could you post pictures of your solar set-up? Did you buy all the components from the same source? I am solar ignorant but willing to learn.
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Old 10-08-2014, 05:52 AM   #3
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No pics yet, I am a little challenged in that department but working on it. I will try and photo document my installation in the coming weeks/months as it unfolds. I bought everything from Renogy Solar, but off their ebay store. They sell through many channels, ebay, Amazon, direct, maybe others but ebay turned out to be the cheapest. I don't know anything about the company but don't think they make anything, they are just packagers and marketers.

I was impressed that I could get on their site and get pretty quick answers to my questions via their "chat" function. I will highlight one thing though. They sell "kits" and nearly all of the assorted giblets to install a system, panels, wire, connectors, controllers, etc., but do not offer any fusing. Even though their own diagrams that come with the equipment shows fuses. When I asked about this they said go get some on Amazon. I thought that was lame and they could provide the correct bits.

This led me a conclusion that there are probably a lot on solar installations out there either fused improperly or not fused at all. Not in my egg I tell you. I have spent a ton of time researching solar on the internet and there is a great deal to be learned from the installations on here from fellow FGRVers. This is a very handy and helpful bunch.
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Old 10-08-2014, 06:14 AM   #4
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Is the 20 amp charge controller going to be enough?
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Old 10-08-2014, 08:25 AM   #5
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Is the 20 amp charge controller going to be enough?
I hope so, but if I had to do it over I may have gone with a 30. Although my rationalization at the time of purchase was the MPPT controller can handle 24V input, effectively doubling the panels it can serve and probably increasing efficiency in the bargain. The controller actually says 260W max panels at 12V (520W @ 24V). I think this has a pretty big margin (reduction) calculated in and if I am deploying the (third) 100W portable panel it is because the other two are in the shade and not producing. I may end up buying a 60W panel for portable use just to be safe and more convenient.

I realized I did not describe my solar plan. I intend to mount two 100W panels flat, permanently on the roof of my Scamp. I will route the wires down through the roof in one corner of the shower (got the idea from another FGRV member) and then into the front street side storage compartment under the front bunks where the controller (and maybe an inverter) will be mounted. Two new 6V “golf cart” batteries will be mounted on the tongue in a new rack I am fabricating. I will also have a 100W (or 60W) panel loose for portable use in case I am parked in the shade or it is really cloudy for several days or such.

I fully expect this system to work and to fulfill all my needs, if it is not over kill most of the time (over kill is OK). In my research I learned that solar is as much an art as it is science, and designing a system requires a lot of assumptions. First is of course your needs/usage. This alone can be harder to figure than it would initially seem. For instance, what got me started on this was me wanting to run my CPAP from a battery for camping and power outages. The raw data on amps from the back of the CPAP multiplied by volts would indicate an inverter over TWICE as big as the CPAP manufacturer recommended to me and I eventually bought. I have subsequently ran my CPAP off a battery through this “half-sized” inverter and found it entirely satisfactory. This is the dilemma faced by the solar newb, what is your actual demand? And what do you need to satisfy it?

A lot of information can be found on the web, including very helpful sites like the “12 volt side of life” and others. You can get close, or at least pointed in the right direction with the math demonstrated on these sites. The arithmetic itself is not that hard but as I say some assumptions have to be made along the way. One little complete WAG (wild a**ed guess) rule of thumb I picked up in my reading was double (almost) everything. Like battery AH (amp hours). Right off they say for maximum life you never want to discharge your batteries below 50%, and even less regular discharge is better. So right there you need a battery bank twice as large as calculated, and more gives you more life and more cushion in case of issues recharging or increased loads. The same applies to panels. Panel output is given under ideal conditions, which you may rarely get, or get for long enough to fully do the job of completely recharging the batteries.

Most of us will mount our permanent panels flat on the roof, which is not the “optimum” angle most of the time reducing output. We may park in the shade some, or our panels may be dirty or really hot with reduced cooling airflow underneath and around, all of these reduce output. So, more “array” (panels) than the pure math indicates will probably be required. Wire size is another, bigger is better to reduce voltage drop and resistance. This may sound insurmountable, and a fellow may be tempted to chuck it all in favor of shore power sites or a generator (gasp!) but it is very doable, and many here and elsewhere are doing it very successfully. I intend to get my system in and test it in the backyard, nothing says I can’t camp right here!
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Old 10-08-2014, 08:42 AM   #6
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With 300 watts of solar panels , how many , what type, and size batteries will you be using ? My 99 Scamp only had a single 27F battery and I was told that one 100 watt solar panel was sufficient under normal usage . A friend of ours retrofitted his electric golf cart to charge with solar ( 6-6 volt batteries == 36 volts total) . He uses 3-100 watt panels mounted on the roof of the cart and has no problem keeping the batteries charged. Disclaimer "I am not questioning your judgement or your design nor do I hate solar " I am just curious how the total system is integrated
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Old 10-08-2014, 09:02 AM   #7
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[OMG--you said the "G" word.] .....All I want is to be able to keep my twin 6's fully charged so I can dry camp to my heart's content, without worry. Got all LED lights, so prime power drain is the furnace, the water pump, the Xantrex inverter, the porch light-- etc. Fortunately do not have the more serious power needs. Will follow your progress with great interest. I admit a lot of tech detail flies right over my head. One thing I would not do is install panels on my roof.
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Old 10-08-2014, 10:23 AM   #8
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Originally Posted by steve dunham View Post
With 300 watts of solar panels , how many , what type, and size batteries will you be using ? My 99 Scamp only had a single 27F battery and I was told that one 100 watt solar panel was sufficient under normal usage . A friend of ours retrofitted his electric golf cart to charge with solar ( 6-6 volt batteries == 36 volts total) . He uses 3-100 watt panels mounted on the roof of the cart and has no problem keeping the batteries charged. Disclaimer "I am not questioning your judgement or your design nor do I hate solar " I am just curious how the total system is integrated
I plan on two 220 AH 6V conventional flooded cell batteries. Hooked up for 12V the AH is not accumulative so 220 AH total. My research on conventional wisdom (see WAG in post above) seems to indicate 1 watt of panel per AH capacity in an average system. So, two 100W (200W total) permanent panels should get me close with the portable to pick up slack if required. Hence the remote meter install so I can keep an eye on things and only deploy the portable panel if necessary or desired. I donít mind at all being questioned, I am not flying completely blind but have not performed or observed any real world experiments on what I am trying to do so it is all supposition for me at this point. But I am putting my hard-earned on the table and doing it. Best case scenario I find that my system works much better than expected and the Sun always shines on my camping trips and I never pull the portable panel out. My batteries will not discharge much and last virtually forever. Yea!

I forgot to mention that next year's major purchase is a new 12V compressor refrigerator and I want to be sure I have the capacity to power it (indefinitely). I don't want to get into a discussion (but will if you insist) of the pros/cons of a 3-Way vs. a 12V compressor refrigerator, it is just the best choice for me and dang it, I will have one!
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Old 10-08-2014, 10:39 AM   #9
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I plan on two 220 AH 6V conventional flooded cell batteries. Hooked up for 12V the AH is not accumulative so 220 AH total. My research on conventional wisdom (see WAG in post above) seems to indicate 1 watt of panel per AH capacity in an average system. So, two 100W (200W total) permanent panels should get me close with the portable to pick up slack if required. Hence the remote meter install so I can keep an eye on things and only deploy the portable panel if necessary or desired. I donít mind at all being questioned, I am not flying completely blind but have not performed or observed any real world experiments on what I am trying to do so it is all supposition for me at this point. But I am putting my hard-earned on the table and doing it. Best case scenario I find that my system works much better than expected and the Sun always shines on my camping trips and I never pull the portable panel out. My batteries will not discharge much and last virtually forever. Yea!
Thank you!! I talked to our local solar contractor and took a short course in solar at our union's school (IBEW) . They talked about matching your solar system to your load and battery capacity . They indicated that installing a large solar system without regards to proper battery / storage capacity could be counter productive and that different types /sizes of batteries have different charge rates. I am learning just as you are so my questions are only an attempt to educate myself
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Old 10-08-2014, 12:23 PM   #10
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If the panels are connected in parallel, the voltage stays the same but the amps are added.

For example:

(2) 100 watt panels

Each panel is 12 v
Each panel puts out 100w/12v = 8 amps

So the 2 panels connected in parallel would result in 12 v and about 16 amps. In real life, I think the amps are between 6 and 7, not 8. Three 100 watt panels connected in parallel would still be 12v and a total of about 20+ amps.

I'm relatively new at this too, so if this is incorrect, someone please correct me.
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Old 10-08-2014, 12:45 PM   #11
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I'm relatively new at this too, so if this is incorrect, someone please correct me.
I think youíve got it. I confuse which is which, series or parallel. I understand the wiring to achieve each one just get the names confused and have to refer to a chart I did up. I wrote on it: "Parallel, same voltage. Series, same current (amps)". And then you can get into series-parallel wiring.
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Old 11-02-2014, 08:52 PM   #12
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My cobbed together kit, (cost me $431.00 not including the stuff I bought and did not use) ... now up and running just fine.
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Old 11-03-2014, 12:19 AM   #13
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Too much.....

I must admit all this solar stuff gets a little too complicated for me to grasp/understand most of the time...you guys are sounding like rocket scientists compared to me....

last fall I bought a 40W solar panel "kit". (It's a Coleman....and no you can't boil water on it) this thing came with a simple charge controller that has 3 lights (red, yellow, green for no output, charging and charged)....and all the cables, plugs and extension wire included so no real wiring was required except for the battery connection.

the panel has a "brochure" output of 3 amps....2.3 is actual in the real world (I am told that all panels are rated/behave like this)....the controller is rated at 7 amps (so, supposedly, one could run two panels off one controller and still have a safety margin left over)

I did not hard mount the panel...besides being nervous about drilling holes in this "new to me" trailer I wanted to be able to deploy it away from the trailer (the shade and perfect angle thing)

I mounted the controller and extension wire in the tounge storage locker and the panel lives inside the trailer.

All I have to monitor performance/usage is a panel meter inside the trailer. I used it this summer and have been really pleased with it.

Last week I bought another one (same item, same "kit")....I bolted two heavy duty suction cup tools to it and that one is now "semi-permanently" mounted on the roof of the trailer, beside the fridge vent. The wire runs down the vent to the contoller I have mounted inside the fridges "workings" compartment....and connected the controller output wires to the block (+/-) that feeds the fridge (using the fridges 12 volt supply wires in reverse kinda to reach the batteries)...the panel itself sits about half an inch above the FG (ventilation) and is in the lee of one of the max air covers up there when driving down the road (wind)

So I guess I'm running TWO solar systems...one is on "all the time" on the roof (at least when the sun is out) and the other one is as before... deployable when and if....

I suppose if I stayed in one place long enough I could get up on the roof and take the "semi-permanent" one down to set it up at a perfect sun angle too....but that sounds like work and probably won't happen very often if at all

I have no idea how this is going to work as far as amps/watts yada yada compared to a more sophisticated set up....and with only a panel meter my findings will just be anecdotal at best....but it's kinda fun playing around with this stuff though...too bad I won't really find out how it works now until I hit the road again in the spring....(any and all comments most welcome BTW)

anyway thanks for posting all of that...makes for interesting reading...looking forward to updates/progress....cheers and happy trails, F
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Old 11-03-2014, 08:52 AM   #14
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Nice looking set-up. I'm not at the rocket scientist level either, I cobbed my kit together in the garage, thanks to info from the great minds on this and the Escape forum.
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