Solar Panel Installation

Wavery · 01-10-2010, 06:17 PM

I got an 80W Solar Panel for Christmas so I just ordered a duplicate to it so that I will have a 160W array.

I am thinking of mounting the panels on the front part of the rear (lower) roof. I want to mount them so that they are covered by the front roof when the trailer is closed.

I was wondering if anyone has ever researched doing that. I have 2 concerns:

1. Is there enough room between the roofs with them closed? I'm thinking no...

2. Is the overlap far enough (36") between the front of the lower roof and the back of the upper roof?

My panels are 26 1/2" wide, 36" long and 1 3/8" thick. They weigh 14# each.

01-10-2010, 06:30 PM

The only way you can find out for sure... 1) Lower the rear shell, go inside, and measure from the mark the seal makes on the roof to the front edge. And the most fun 2) Go inside with a flashlight and a ruler, get real small, and have someone lower the front shell. Make sure it is someone you trust so you can be sure they will raise it when you are finished measuring. Let us know what you find out!

01-10-2010, 07:36 PM

It looks to me like there is only about 3/4 inch between the shells when closed.

Wavery · 01-10-2010, 08:09 PM

Quote:

Originally Posted by AstroBruce

It looks to me like there is only about 3/4 inch between the shells when closed.

That's sorta what I was thinking.

I think that I will make a cardboard mock-up of the panels and try that. I just have to wait until I'm getting around a little better.

The other thing that I was thinking was to make a couple of brackets that hook the edge of the roof (kinda like the brackets that some people hook over a bathroom door). Store the panels on the bed while closed then when we open the upper shell, pull the panels our and hook them on the forward part of the rear shell, then open the shell.

My concern is that I'd like to make them as theft proof as possible. Out-of-site, out-of-mind tends to work well for that.

**ShrimpBurrito** · 01-10-2010, 09:08 PM

Wayne,

If you follow the attachment procedure spelled out by forum member RockyMtnRay, I seriously doubt anyone would be able to steal the solar panels without a power saw. And if they are willing to use a saw, there's alot more they can steal.....

Of course, a major benefit of having them exposed while the TM is closed is you get charging current while underway, sitting in a parking lot while at a restaurant, visitor's center, etc. In my view, those benefits would far outweigh the risk of theft. But I've never had solar panels, so I don't really know how attractive they are to thieves....but I think they'd be far more difficult to steal than a car stereo.

Dave

**rotor_wash** · 01-11-2010, 07:34 AM

Don't forget the value of letting the sun keep your batteries topped off. I mounted mine on the front and use a MPPT controller for a three step temperature monitoring charge. Don't go cheap on the controller even if it is another high priced item on the solar list. It's what makes it work well. I also used Rocky Mtn Ray's mounting idea that used both the Loctite adhesive and 3M VHB tape on alternating mounts. The tape is designed to replace rivets and other fasteners and have some vibration reducing effects.

Wavery · 01-11-2010, 09:45 AM

Quote:

Originally Posted by rotor_wash

Don't forget the value of letting the sun keep your batteries topped off. I mounted mine on the front and use a MPPT controller for a three step temperature monitoring charge. Don't go cheap on the controller even if it is another high priced item on the solar list. It's what makes it work well. I also used Rocky Mtn Ray's mounting idea that used both the Loctite adhesive and 3M VHB tape on alternating mounts. The tape is designed to replace rivets and other fasteners and have some vibration reducing effects.

I'm not exactly new to solar power. I used solar panels on my yacht for 10 years while living aboard (24/7/365) and sailing around the world. Trust me, I have more real-world experience with solar than most. I didn't use a controller then and I have no intention of using a controller now.

Remember controllers only have the ability to do one thing. That thing is to turn off the solar panel output when the battery voltage (in some cases, battery temp) reaches a certain point. Controllers do NOT have the capability of increasing the amount of output from the solar panels. This is a fallacy. In fact, the controller itself uses power to operate, thus being a net loss.

Unfortunately, these panels have a built in diode to keep the batteries from draining back into the solar panels at night. The diode requires nearly .5A of charging current to overcome the "Gate" and allow the panels to charge. This .5A is lost throughout the charging cycle. I personally would rather simply disconnect the panels at night and have that extra .5A of charging throughout the day.

Don't get me wrong, controllers are great if you have a small battery bank or a large solar array or if you just want to leave the panels un-monitored over long periods of non-use of your 12V system. I have none of that. I have a fairly large battery bank (2, Trojan T105 6V golf cart batteries) for 160W of solar panels (160W is a relatively small array) and I doubt very much if my batteries will see 14+V during any one day of camping. I have no intention of leaving the panels hooked up if we leave for days at a time or when in storage.

Controllers are also capable of giving you the optimum "full" charge. However, when I am camping, this is not likely to be an issue because we use our electric a lot.

I have a digital volt meter that I place right at the batteries and it is in plain view. In the unlikely event that I see the battery voltage over 14V, I will simply disconnect the solar array (flick of a switch). If the voltage goes beyond 14.6V for a few hours of un-attention (which is extremely unlikely), that's certainly not going to hurt anything.

Remember, as your batteries increase in voltage they also increase in resistance to the amperage that is put out by the solar panels. The higher the battery voltage, the less amps that the panels can actually deliver to the batteries. For the most part, this is a pretty self-regulating system.......to a point. If the panels are in direct sun (which is seldom on permanently mounted panels) they ~may have the ability to over-charge, fully charged batteries at the peak of the solar panel performance (maybe 1-2 hours a day, if the Sun is passing directly over-head). I will be very happy if these panels simply keep up. I am not at all concerned about over-charging or getting the best capacity charge possible. These are the things that sell controllers. They are simply not reality. I have nearly 100,000 hours of first hand experience using unregulated solar power. For ME.......it's a non-issue.

**Bill** · 01-11-2010, 09:57 AM

Wayne -

Couple things.

First, since they are nearly black and designed to be very absorptive, the panels get quite hot in direct sunlight. They depend on having some clear air space on the back side of the panel for cooling. If you mash them up against the trailer roof, you cut off the air circulation. This risks damaging the panel, and doesn't do a whole lot of good for the roof. In addition, their ability to generate charge drops with increasing temperature.

Second, the blocking diode does not require 1/2 amp of current to overcome the "gate" - I'm not sure what that term means, as there is no "gate". I think you are referring to the fact that a diode drops about 1/2 volt of voltage as it conducts current. Since the panels generate more than 17 volts, and you need less than 15 volts at the battery or the input of the charge controller, the 1/2 volt drop doesn't cost you anything.

I suppose you could argue that the 1/2 volt would mean something if you were using an MPPT charge controller - but I don't think anyone would spring for an expensive MPPT controller on a 160-watt array.

I recommend that you follow Dave / Shrimp Burrito's suggestion, and read the threads (I think there were several) in which Rocky Mtn Ray described his reasoning, his experiences, and his results. He laid out his thinking over the course of a year, I think, and I have never seen a better description or guide - even on the solar power newsgroups and forums.

Bill

Wavery · 01-11-2010, 10:01 AM

Quote:

Originally Posted by ShrimpBurrito

Wayne,

If you follow the attachment procedure spelled out by forum member RockyMtnRay, I seriously doubt anyone would be able to steal the solar panels without a power saw. And if they are willing to use a saw, there's alot more they can steal.....

Of course, a major benefit of having them exposed while the TM is closed is you get charging current while underway, sitting in a parking lot while at a restaurant, visitor's center, etc. In my view, those benefits would far outweigh the risk of theft. But I've never had solar panels, so I don't really know how attractive they are to thieves....but I think they'd be far more difficult to steal than a car stereo.

Dave

I have a rather unique parking situation for my TM. I park in an apartment complex garage along with 80 other people. I also manage the apt building.

My concern is not so much the tenants. My concern is vandals that sneak into the gated garage on occasion. These vandals can see inside the garage from outdoors. If there is anything left in plain site, that becomes an enticement to them. I want no part of that. My intention is to leave the solar panels out-of-site while in storage. Even if the panels are impossible to get off, the vandal might then turn his attention to what he can find in the tenants cars. This is an afluent part of town and we have a lot of nice cars in the garage but not everyone remembers to lock their doors and set their alarm. Every once in awhile, someone gets things stolen out of their (unlocked) cars.

Heck, vandals steal solar panels off of the freeway emergency phones and other equipment, all the time. Stealing a much larger array in a garage, with little chance of detection (at 3:AM) would be quite enticing.

Wavery · 01-11-2010, 10:18 AM

Quote:

Originally Posted by Bill

Wayne -

Couple things.

First, since they are nearly black and designed to be very absorptive, the panels get quite hot in direct sunlight. They depend on having some clear air space on the back side of the panel for cooling. If you mash them up against the trailer roof, you cut off the air circulation. This risks damaging the panel, and doesn't do a whole lot of good for the roof. In addition, their ability to generate charge drops with increasing temperature.

Second, the blocking diode does not require 1/2 amp of current to overcome the "gate" - I'm not sure what that term means, as there is no "gate". I think you are referring to the fact that a diode drops about 1/2 volt of voltage as it conducts current. Since the panels generate more than 17 volts, and you need less than 15 volts at the battery or the input of the charge controller, the 1/2 volt drop doesn't cost you anything.

I suppose you could argue that the 1/2 volt would mean something if you were using an MPPT charge controller - but I don't think anyone would spring for an expensive MPPT controller on a 160-watt array.

I recommend that you follow Dave / Shrimp Burrito's suggestion, and read the threads (I think there were several) in which Rocky Mtn Ray described his reasoning, his experiences, and his results. He laid out his thinking over the course of a year, I think, and I have never seen a better description or guide - even on the solar power newsgroups and forums.

Bill

You're right....I meant 1/2V not amp duhhhh!!!. However, it is a net loss over the charging cycle. When I was on my yacht, I used a diode when I left the boat for long periods (those panel did not have a built-in diode). I had a pretty expensive digital battery analyzer on the boat. The difference was provable when having the diode hooked-up during the day while charging. I used to have notes in my log on all this stuff but I've long since lost my ship's log. It's a mute point because most panels now have built-in diodes.

I also considered the heat issue with the panels. I can drill 3/4" holes all around the perimeter of the frame to help with air circulation and heat removal. However, I am leaning toward storing the panels inside the camper and putting them on the roof (on risers) before we lift the rear (lower) roof. It's just another step during set-up. I have spent a lot of time ad energy eliminating "steps", I'm not exited about adding a step.