Solar Panels on TM??

[Sinclue]

Dick,

I got the panel off of eBay for $225 with drop shipping direct from Siemens (a brand new panel).  I used a 50' orange powercord (14g) that I cut the ends off of. I used orange for visibility when the panel is on the ground. I had thought about using 12g, but I tested both the 12g and the 14g and the loss of power was only about .15amp.   I wired one end directly to the panel (clearly marked, easy to do) and the other end I connected to a small 7amp charge controller I got from Camping World (about $50 with discounts/sale as I recall).  The charge controller (a must) is then attached to the batteries directly with ring terminals(could be clamped) which are in the back on my rig. I did not, however, connect the green grounding wire at the controller end (did attach it to the panel's junction box for possible future use). I also attached some white rubber "feet" on each side of the frame so that I could rest it in any position without marring any surfaces.  For travel I just wrap the cord around the panel and lay it on the couch.  Last trip I propped it up against a tree in the AM and slid it onto the roof for the afternoon sun.  Its pretty lightweight so that an "old geezer" like me can handle it without any problems.  My wife had some concerns that somebody might walk off with it, but I pointed out 4 or 5 generators at campsites that were much more attractive bait than a 2'x4' solar panel.  It would only take a couple of seconds to pull up and unplug a generator and stick it in a vehicle and be gone. Hope this helps.
jim

Well, Jim
It sounds as if I'm in the Ballpark. I did the same thing with a 14g extension cord yesterday. I bought a BP Solar 75W panel plus 8 amp charge controller off of ebay. I mounted the controller inside even though the lit sez it's blahblahblah-proof. We have a 3023 with the loveseat option, so rather than lose the drawers that are built into it, I built a frame out of 3/4" plywood and added it to the top of the loveseat frame. The BP panel fits nicely inside, and it "only" raises the cushion 3". When we're in a park the solar panel + wiring will be out of sight and safe from damage.

I'm going to add PVC legs to the short sides capped at both ends. They'll pivot inside of the panel and should allow me to set the panel up anywhere that's level. I'll have to devise a way to prevent the panel from blowing over, though.

Incidentally, what did you use for the feet/bumpers?

Dick

Hey, Jim-
I got distracted by TS Bill blowing tree limbs around outside and forgot to ask: no problems with 50' of cord? I want to be able to set up in the sunniest spots, but am concerned about voltage drop and overheating on the 14g stuff. I was thinking more along the lines of 20-25', but would prefer 50. What is your experience?

Dick

[Sinclue]

Dick,
I used some leftover moulding from my sailboat.  Its kind of L shaped with a rounded "bead"  (3/8' thick)that runs along the outside of the L.  Marine supply stores or online should have it.  Its made to be exposed to sunlight, saltwater, etc, but is pretty flexible.  
I tested both a 50' 12g and 14g cord.  The amps delivered to the controller only dropped .15amp(+/-) in direct sun. In heavy shade where only about 1amp is being generated (or less) that is a more significant drop.  But with a "mobile" setup shade shouldn't be as much of an issue.
And as there is, at most, some 4amps being generated by the 75w panel, overheating isn't a problem.
Your setup sounds good to me.  I should probably mount my controller inside too, but I enjoy being able to glance over occasionally and see that yellow charging light glowing brightly (and it even went to the green "full"  light a couple of days!)  8)
Jim

Jim.
Thanks for all the help. One last question: how exactly do you measure amps? I've never been able to figure out where to put the probes or how to set up the multimeter. I have a Cummins digital multimeter, and have no prblems with volts or ohms. Amps I don't get. ???

Dick

[Sinclue]

Dick,
For electrical expertise I defer to Bill (who hopefully will add to our/your storehouse of knowledge on this subject).  I have a cheap-o multimeter that reads up to 10amps.  (Most seem to only meausre milliamps).  I simply measured directly to the wire ends. I left them twist connected to the controller inputs initially so that I could do some measurements in different situations/locations.  I just removed the wire nuts to take the measurements.  At max the output is about 4amps, but remember to always be careful with this stuff.  As they say, it not the volts that will kill you, its the amps.  Even at 12v a 4amp jolt will get your attention right smartly.
Jim

Bill, Et Al -
Correct me if I'm wrong here, but technically, Amps are the unit of measure for electrical current in a particular circuit at a given voltage through certain Ohms resistance in the wire.

1 amp would be 1 volt of current moving through 1 Ohm of resistance...

Anyway, if you have a multi-meter, you should be able to measure amps by selecting the AMP setting on the multi-meter.

Amps are really what we need to pay attention to. Our batteries will only hold so much power - AND AMPS are the current the withdraws that power. So to fully utilize your solar set up, you must understand how many AMPS you use when drawing from the battery.  Remember that the AMP rating for the given piece you use (appliance) (Lights, TV, HEATER, Water Pump... etc) times the number of minutes - hours per day you actually run (turn on) these appliances will determine your AMP HOUR draw. THIS FIGURE will tell you if you have enough battery capacity, and enough solar re-charge capacity in your panels.

You can add an Ammeter to your system to check your amp usage. Add it to the positive side of your main power (+ side of the battery) only. The Ammeter is an electrical flow meter, telling you how many Amps you are using at a given moment in time.

I installed a traditional automotive style round 30 Amp analog unit with a sweep type face dial in mine. I also have a 2" round analog Voltmeter on my tounge up near the battery.

If I'm reading these posts correctly, I think that JP measured his amps at the wire ends for his solar panels -- in full sun?

Don't grab both wires when you're doing this, as that'll get your attention real quick...

Hope that helps!

Gregg

 I'll attempt to answer a few of the questions about solar panels that have come up while we were away attending the TrailBlazer's Jubilee.
  I mounted 2 75 watt panels in a flat, fixed position on the roof of our TM. Yes,  the panels are in the shade for part of the day and I could probably realize the same total output from 1 panel by moving it out to a sunny area but there are some considerations in this approach. You would need to be around all day to move the panel as the angle of the sun changes unless you are in a totally open area in which case there is no advantage in having panels on the roof vs. moveable panel(s).
  I also did not want to deal with moving the panel around and finding a place to store it while traveling. It would be just one more thing to deal with when changing campsites.
  Our trailer is stored in a location without electricity nearby and the roof mounted panels keep the batteries charged. No fuss, no muss and no extra work.
  I carry a compass with me when we are choosing a boondocking campsite. I first check for an opening above the roof that will allow at least a few hours of sunlight during the day. With 2 panels this is enough to recharge the batteries from the previous evening's use.
I then check the compass to see where the sun's path will be. The best position is with the front of the trailer pointing north, trees on both sides for shade in the morning and evening and an opening overhead to catch the bright noon sun. Yes, that means that the site is warm during the middle of the day but that is what we have an awning for and usually we're out doing activities during that time so the lack of shade is not that big a consideration. Sometimes we have to make do with an eastern exposure - not as good because the sun is weaker in the am. An east-west orientation with a clear overhead is good for charging up discharged batteries but not as good for comfort in the afternoon because the sun can get under the awning.
  I have never heard of anyone running an air conditioner on an inverter. I do not think there is an inverter made for rv use that could feed the hungry compressor nor would you have room for the the large number of batteries and solar panels needed to run the thing. You will have to make do with 12 v. fans.
  Our solar setup runs the power from the panels down the front upper half to the hitch where it connects to the charge controller. From there it goes to the batteries mounted behind the propane bottles and then under the trailer and up through the floor to connect to the converter through the terminals for the inside battery connection. All connections except for the converter connection are outside the trailer. We just recently purchased a digital camera and I will take some pictures soon and attempt to post them here.
 
Good luck all you TM tinkerers,
Bruce Martin
 

 

[Sinclue]

Bruce,

Definitely good points on the fixed installation.  It is one more thing to do in setup/takedown, but its only 5 minutes or less.
As we mostly boondock we don't tend to be away from the trailer all day, but if we were I could set the panel in a location where it would receive the same amount (or more) of sunlight as any fixed installation.  Plus, I don't have to work it out so that the trailer will be in the sun at all.  I can pick the best spot for the trailer when I setup, not the best spot for my solar panel(s).  

As we generally don't use more than 20amps in a day it really isn't much of an issue for us.  Our battery setup allows for over 200amps available (2@6v) so even a couple of hours of direct, or even indirect, light takes care of our needs.  

One other factor to consider that I'm not sure has been mentioned is that the amount of dirt, crud, etc that attaches itself to the solar panel has an effect on the amount of charge it will generate.  How often do you clean your panels and how easy is it to do?  At our last campsite a significant amount of pine needles and just plain dust wound up on our roof.  

But really it come down to personal preference I think. I didn't want the extra weight(and the attachment holes) on my roof sections.  I guess that many are attached with an adhesive so that would eliminate the holes mostly, but I've experienced some significant adhesive failures in projects over the years (has anybody ever gotten "SuperGlue" to work on anything?) and I'd hate to see my solar panel bouncing down the highway behind me.  

I agree that using any standard RV inverter to try to run AC is out of the question.  There are inverters that would do the trick, but as you point out they are large and bulky and require a significantly sized battery bank to operate.  If you are going to need AC then you'll need hookups or a noisy generator(and yes even the so-called "quiet" ones are noisy to those not using them, especially in more remote campsites where there isn't all the ambient noise that you have in the city).  As you can guess, I'm not a big fan of generators.  Hence this thread.

At any rate, fixed or mobile, we seem to all agree that solar is a good way to go and that is the real bottom line.  With all these responses those still thinking about it have pretty much all the information they need to make a good choice for their own particular needs.  I love this board!

jim

  Good to hear from you Jim, and I  definitly dig the talking heads reference!
  As far as the glue job goes I did not use super glue on the 3" X 20" aluminum  mounting feet in the center of  the roof. RV Solar Electric recommended using Liquid Nails and I have had no problem whatsoever with it's holding strength. In fact if  I ever buy another trailer and want to take  the panels off I will have to leave the feet attached and paint them white to match.
 The panels and mounting hardware have surived the infamous South Dakota Jubilee hail storm of 2000 and over 15,000 miles of camping all over the US and Canada.
  But as you say it's having the solar option that is the important point here, not how or where we mount the panels.

Burce