Doing Solar Again

I now have the RV and it has a lot of shade free real estate on top. I am going to put the solar near mid-ship between the 2 AC's and drop the cable down the Bathroom sink vent. I'll exit the vent line in the bathroom vanity and below that is a huge chase where most of the wiring is located. From there it will be an easy run to the controller location which is right next to the batteries.

My controller can take up to 30 volt and output 12 volt nominal with only a 1% efficiency loss over 24/24. My stepson is a solar installer and is going to get me some panels at .80/ watt. He has already put some on his RV.

I'm not opposed to drilling a hole in the roof. The RV will be delivered to my home on Monday so I'll have to wait until then to evaluate it. Who knows, it may be solar ready. I forgot to ask.

With 24v, I'm hoping to go with #8 or #6 wire depending on the distance.

Hi,

This should be an emergency solution only. It is a bad idea. DAMHIK

BFL13 wrote:
You can also "tap" the 24v bank for 12v, but this is unbalanced draw so you would shift the tap from time to time in order to keep them even.

What about the controller's 60Voc limit? Will that not make parallel wiring the 24v panels a must?

pianotuna wrote:
Hi,

Two possible ways;

a. a dc to dc converter (2oldman has done this)
b. a converter powered by an inverter

CJW8 wrote:
Don,
How then do you do you break out your 12 volt loads?

You can also "tap" the 24v bank for 12v, but this is unbalanced draw so you would shift the tap from time to time in order to keep them even.

Don't forget my tests showing that 24-24 PWM gets the same output to the battery as 24-24 MPPT using 60 cell panels.

If you did the 24-24 and bought a converter for the 12v stuff the price diff between PWM and MPPT controllers would easily pay for the converter.

The snag is getting a 24v inverter if you already have an expensive 12v inverter.

RJsfishin wrote:
Its very simple. You want the shortest route to the controller, so you come down thru the roof as near to the controller as possible. Mount the combiner box on top of the hole, and be done w/ it.
If you are the type that can't drill a hole thru the roof, then I feel for you,....or do I ??

Tilt bars are made from aluminum flat bar, and mounting brackets are made from aluminum angle,.....at 1/3 the price.

I found hat that having the controller close to the batteries is more important than close to the panels unless the controller has remote battery voltage sense.

Our fridge is in a slide too. The tech brought the cables down alongside the tank vent. A friend who has an identical rig brought his down under the rear cap.

Here is a picture of my roof coating on my Bounder. it has close ups of the solar mounts, and shows one of the larger and much longer tilt arms on the small pair of panels. (so it is tilted about 90 degrees while I was working under it).

It also shows the tamper resistant 1/4-20 stainless steel bolts and 'nutserts' that are riveted into the panel frames. You can google Nutsert on Youtube and see how they are installed. You can buy nutserts at Grainger.com

I had to rivet a bracket onto the front solar panel near the sidewall, so that it makes up for the extreme roof taper to the sidewall, due to them being so close to the side of the RV. 120 watt panels are 'huge' in the front. I can not imagine how large a 200 would be up there.

The air under the panels helps keep them much cooler, and you get more amperage from them when they are cooler. Best amperage I ever got was at Thanksgiving at 4,500' elevation, with light snow on the roof reflecting additional light onto the panels, that where tilted south at about 45 degrees.

Golden_HVAC wrote:

rickthescot wrote:
Sounds like a great idea. I guess asking for pictures again is not going to persuade you though. We are visual creatures and I don't think 1000 words will accomplish what one image will. You can do it, just one pic.

More pictures that I took a few days ago to post pictures of my solar panels, and their mounts. Some pictures are really close up pictures of the solar panel mounts, and give a clear picture of howrough the surface is.

Golden_HVAC wrote:
Hi,

This is my front pair of panels. 120 watt mounted on a curved roof, 102" wide.



This is the mount it is held on with three rivets into the frame, and then the bottom half is 6" long aluminum, with nutsert in the upper piece, bolt you can not see from the outside edge pointing inward.









This picture shows the bigfoot panel mount sold by RvSolarElectric for $35 a set back in 1994. I wonder what they cost today?


This picture shows the panels tilted while I was working on the roof.

Fred.

Sun electronics sells a 140 watt 12 volt nominal panel for around $229. You can check their website for others. You will want something with a frame, so that you can bolt it to your roof.

What I do for roof mounts are 6" long of 2" angle aluminum from Home Depot, with three holes for the roof 3/16" and #10 screws. 5/16" hole for the 1/4" bolt to the panel frame.

For tilt rods, I used 1/8" thick 3/4" angle aluminum. 18" long is large enough for my panels. 5/16" hole in each end, with one going into the roof mount, one to the top side of the panel.

My problem is that 400 watts was plenty to charge my batteries, and I did not want to put excess wear on the roof, so I no longer tilt the panels. I would rather buy another panel, than to worry about wearing out the roof, or causing more than $150 in damage to it, or risk my life going up and down the ladder. . .

I used #10 UV rated wire in my original system, pair of 45 watt panels. Then added a 75W panel with the same wire, now about 15 amps. When I installed a pair of 120 watt panels, I ran a new #10 gauge line. While larger wire is recommended, it does work, due to the short wire length.

You could use 24 volt nominal panels or 12 volt in series, or whatever you like. Just remember that 200 watt panels are really large, and might be difficult to locate several of them on the roof, with all the vents and A/C that is already up there.

For my van, I plan on drilling a hole right in the middle of the roof, then go to the sidewall. On the roof, the hole will be covered by the solar panel. I will also be installing a fantastic fan there as well.

For my satellite dish, I put the hole over one of the A/C vent air ducts, and that worked out fine. When it did leak, it was into the air duct, and did not damage anything, we found the leak in minutes. Then repaired the leak (due to the wires twisting when tuning in the dish).

On my motorhome, there is a panel running along both sidewalls. I can remove that panel, and there are factory installed wires there, and I installed more wiring there.

Good luck!

Fred.

hi,

Because the limitation is about 400 watts with the 3024 running 12 volts, and 800 watts running at 24 volts.

pnichols wrote:
Don, why can't the OP go with 24 volt panels but stay with a 12 volt battery bank in their RV?

I thought that the better controller's had an adjustable output so that you could set them to around 13.X volts output regardless of the higher input voltage from 24 volt panels?

Hi,

Two possible ways;

a. a dc to dc converter (2oldman has done this)
b. a converter powered by an inverter

CJW8 wrote:
Don,
How then do you do you break out your 12 volt loads?