Solar Panel Install on rear shell - Page 4

OneMoBear · 12-21-2010, 08:54 AM

Thanks Bob! I'll check that out.

Malinda

Wavery · 12-21-2010, 10:32 AM

With a 120W solar panel, the controller may be more necessary. It depends on your battery set-up and how much you enjoy keeping an eye on the voltmeter.

If you have 1, 12v battery, a 7A charge (which would only happen with peak Sun angle) may be a bit much for several hours unless the battery is ~50% discharged.

If you have 2, batteries (either 6v or 12v) the need for a controller is less vital because (essentially) peak charge rate will be ~3.5A per battery and will only occur for a few hours per day with a permanently mounted panel. If the batteries are in good condition, you need only check the voltmeter every few hours to make sure that the battery voltage does not exceed 15V. I would recommend disconnecting if you see 14.8V. Basically, that's all that a controller does anyway.

I have a 160W array and my batteries will top-up around 2:PM on a Sunny day (with normal usage). I would think that your batteries may top-up by the end of the day........all things being equal (I have 2-6V golf-cart batteries).

I actually recommend that people do this (go without a controller) when they 1st start out with solar. It helps the user be more aware of how the panels operate.

Having said all that, if you leave the panel hooked up while the camper is stored outside, a controller is essential.

As for wiring........I have my panels mounted on the rear shell with a short run (~14') to my batteries which are located in the rear of the camper. I use 10G marine grade wire and it is adequate.

Your batteries are located on the front of the trailer. Because of the long run to the batteries, I would recommend using the 8G wire that is available from the solar companies. Although you could get away with 10G, I would not recommend it. If, in the future, you decide to add an additional panel, you will absolutely need the 8G wire. There is no sense in buying and running the wire twice.

As far as controllers go, there are as many selections as you have $. I have this simple 20A PWM controller:
http://cgi.ebay.com/20A-PWM-regulato...item3f05edcd28

The MPPT controllers will give you about 10% additional amperage while charging for ~100%+ more money. In my book, that's not a very good return on investment for these small arrays. I would think that the extra $ might be better spent on a larger panel..........but that's just me. If you take that extra $100 (or so) and put it into a larger array, you could go from 100W to ~150W (a 50% increase in output).

OneMoBear · 12-21-2010, 10:53 AM

First off, congrats on the new baby!

Thanks for the great advice! We also have 2 6v golf cart batteries. Our TM is stored in the garage. We are both quite comfortable with a voltmeter but not terribly reliable to use one

You mentioned the long cable run because our batteries are in front. I know about TMs opinion about this but do you think the panel absolutely has to be on the back shell? We were thinking about just laying the panel on the front panel and VERY CAREFULLY

opening it up to see how much the additional weight changes things . . .

We agree about leaving the center seam accessible and are wondering if it would be worth the extra money for shipping to get two 60s instead on one 120w so we could balance the weight and leave the center open.

I'll check out the controllers.

Thanks!

Malinda

**Bill** · 12-21-2010, 11:04 AM

Malinda -

The air conditioner is on the front shell, and it makes a big shadow. If the panels are on the front shell, they will be at least partially shaded for several hours per day. Though they will be OK at noon, there will be longer shadows during the near-peak solar hours of, say, 9-11 AM, and 1-3 PM.

If the panels are mounted on the back shell, they will be out of the shadow most of the time.

Bill

Wavery · 12-21-2010, 11:05 AM

The problem with putting the panel on the front of your trailer is that the AC unit may shade the panel part of the day. There is also the weight factor.

I would recommend mounting it on the rear shell and simply running the extra distance, under the trailer, to the batteries.

A single panel (of the same wattage) may be a better choice. There are fewer connections, thus less to go wrong over time. Also, you leave the option of adding another panel of the same size in the future (if there's room and a rich uncle dies).

OneMoBear · 12-21-2010, 11:14 AM

Hummmmmmmmmm. The AC is at the very back of the front shell. We were hoping to mount the panel in the front . . .

Malinda

Wavery · 12-21-2010, 11:27 AM

Quote:

Originally Posted by OneMoBear

Hummmmmmmmmm. The AC is at the very back of the front shell. We were hoping to mount the panel in the front . . .

Malinda

Weight may be the determining factor anyway so it may be a mute point.

In reality, the shadow will only effect the panel for an hour or 2 a day and then, only if the Sun rises or sets pretty much in-line with the panel/AC unit. However, the slightest bit of shadow on the panel will have a large impact on the output. When designing a system, maximum output should be a large consideration.

There is very little difference in the amount of work involved, whether you locate the panel on the front or rear. However, the cost of the cable will increase with the distance.

Muddog has the same trailer that you have and he got a really good deal on his 8G wire. You might want to check with him for some tips.

Wavery · 12-21-2010, 01:32 PM

I just thought of another issue with putting it on the front shell.

It will be exposed to a lot of wind (and all that goes with that) up there while towing.

On the rear shell, the panel is 99% protected from wind resistance, rain water while towing, bugs, sand etc.

I'm not sure that I would want 70MPH wind (including head-wind speed) between my solar panel and the roof. Remember, you should have ~1.5" of air space between the panel and the roof.

Take a look at the pic in post #4 of this thread. You will see that the top of the solar panel is about flush with the top of the upper roof while towing.

OneMoBear · 12-21-2010, 05:29 PM

Towing is a great point Wayne. We really hadn't thought of that. Our TVs are about the same and you know that the TM would be mostly sheltered by our truck and camper shell but still . . .

We have window covers that we leave on all the time on the rear shell which are either covered when the TM is closed for towing or protected as you describe by the front shell. The covers for the front shell all go inside when we hit the road. We're sold. Rear shell it is.

Wavery · 12-21-2010, 05:55 PM

Quote:

Originally Posted by OneMoBear

Towing is a great point Wayne. We really hadn't thought of that. Our TVs are about the same and you know that the TM would be mostly sheltered by our truck and camper shell but still . . .

We have window covers that we leave on all the time on the rear shell which are either covered when the TM is closed for towing or protected as you describe by the front shell. The covers for the front shell all go inside when we hit the road. We're sold. Rear shell it is.

Just to make yourself feel better about it, take a 40#.........something.....and put it on the front of your front shell and try to lift the shell. I think that it may be a bit over-whelming. I know that our front shell (on the awning side) is tensioned as far as it can go (maybe yours isn't). There is no way that I could have that kind of weight on our front shell.......at least not on the awning side. If we didn't have that stupid TV antenna, we might be able to have it on the other side but I still prefer it on the rear for all the reasons that I mentioned.