Adding two more solar panels, need advice

[Carolina Fun]

I've got a 2015 Alegro Bus 45 UP. I'm going to add two more 100 watt solar panels. I'm going to tie them into the wires leading from the existing 165 watt panel. I need some advice on how to break through the sealant material the factory used to cover the wires and hole leading down to the charge controller. Can I use mineral spirits to soften up the sealant or would that damage the roof? Any advice would be greatly appreciated.
Thanks

[Pigman1]

First, check how much power the installed regulator can handle. You should have the specs in your paperwork, or an internet search will also work. In addition, check the wire size on the roof to regulator run. Look at the actual cable, do not take Tiffin's word on what they installed. I had a 2008 Bus that they swore had 10ga wire installed and it did NOT. There was 14ga actually on the Bus. Finally, check the length of that run, panels to regulator. You'll have to decide whether to set up the panels as a series or parallel depending on how much losses you'll see in that run and what your regulator can handle.

I've peeled the caulking on wires with a large dull screwdriver and cut the caulking with an old sharpened flexable table knife when I have to separate two items glued together with the caulk.

One final comment. According to all info I've received from various solar designers, if you intend to connect your panels in parallel, they should be a match or very close in specs to get max efficiency.

We have 840W from 6 panels running through a Morningstar MPPT controler.

[okmunky]

The "Going Green" forum http://www.irv2.com/forums/f56/ might find you more help.

[SSG Scott]

Originally Posted by ScottHelmann

I would pretty much ditto that (Above- Pigman1).
1040 watts of panels and a 150 watt fold out panel with a Morningstar MPPT controller- The silence of 60 amps of solar charging while camping in woods is pretty much awesome...

[billdreamlv]

Hey Scott, is it true that when you hook up your solar to an RV, it magnetizes your bus and makes it stick to the earth upside down?

[vsheetz]

Originally Posted by billdreamlv

Hey Scott, is it true that when you hook up your solar to an RV, it magnetizes your bus and makes it stick to the earth upside down?

Good catch. Yes, absolutely true. (-:

[SSG Scott]

Traveling in Australia- the land down under!

[billdreamlv]

Originally Posted by ScottHelmann

Traveling in Australia- the land down under!

Now that's funny.

[Possum]

Originally Posted by Pigman1

One final comment. According to all info I've received from various solar designers, if you intend to connect your panels in parallel, they should be a match or very close in specs to get max efficiency.

Can you point me to this information please? Google keeps giving me paid sites their algorithms think I want to read, not what I am asking for. At present I have a bunch of different sized units hooked in Parallel and with 8 gauge wiring running to the bus bar which leads down to the controller through 8 gauge wire and then on to the batteries via 6 gauge wire. It's been keeping all our batteries charged since last spring when I completed the wiring. TIA

[skypilot_1]

Scott,
Are they flexible panels glued to roof ? Are the wiring harness under the panels ?
Thanks

[Pigman1]

Possum, I got that info while talking to the design engineers at Northern Arizona Wind & Sun. We've bought panels, controller and a number of parts and pieces for our system from them. I was in their Flagstaff office to pick up some pieces and got talking to them about system inefficiencies, and some other way out engineering issues as they related to our system. The guys I was talking to design commercial systems as the core of their business, so I felt they were giving me a straight story. No axe to grind at all. They weren't trying to "sell" me anything, just were being helpful and giving me engineering answers. Their comments regarding the panel matching and efficiency related to my parallel setup and not a series hookup. Further, their point was that even if I had mis-matched panels, MY losses would not be excessive because my panels at max output overpowered my Morningstar 45 MPPT controller. I designed our setup so I got max system output even in partial shade. We use 6ga copper to down run to the controller as our distance is considerable and we also wanted to keep those line losses to a minimum.

As long as your system is doing what you want it to, it sounds like you've got a winner. The main reason for my question to NAW&S was because we had an old panel that had been giving us some problems and I was contemplating replacing it. The question was then should I go to some of the larger (and cheaper $/W) panels or replicate what I had. When you can get these engineers chatting you can pick up a TON of information in a short time. Eye to eye is always best. Hope this helps.

[Possum]

Originally Posted by Pigman1

As long as your system is doing what you want it to, it sounds like you've got a winner. The main reason for my question to NAW&S was because we had an old panel that had been giving us some problems and I was contemplating replacing it. The question was then should I go to some of the larger (and cheaper $/W) panels or replicate what I had. When you can get these engineers chatting you can pick up a TON of information in a short time. Eye to eye is always best. Hope this helps.

Thanks for that. I live in western Canada and my present hookup is keeping everything fully charged by about 4 in the afternoon in very continuous heavy overcast and constant rain. How I wish I could get back down south this winter. Way too much precipitation for my liking but I do live in a rainforest so can't natter too much. Thanks again for your input.

[SSG Scott]

Originally Posted by skypilot_1

Scott,
Are they flexible panels glued to roof ? Are the wiring harness under the panels ?
Thanks

No- they are standard frame glass panels. Flexible panels normally do not hold up very well(long term) to heat and sun. As of my last opportunity to test flexible panels (at this time) they are better relegated to portable installations. UV light after time tends to discolor the panels (much like you see happen to car headlights on sit in the sun all the time).

Now, here is where I deviate from the "norm"- (by the way-I am a retiring senior electronics tech with an EE degree and I tend to be all about logging data and conclusive testing- the proof is in the real life numbers) anyway I have been using Proseal and RTV in aviation for 37 years (its all about the surface prep). Rather than drilling holes in the roof and attaching brackets, the panels are attached to the roof using 50 year RTV silicone caulk. And before people get going crazy- Yes, I do loose a few watts of power due to heating of the panels (data logging in my tests shows it is 2-4%) and the surface temp on top of the panel may be 12-18 degrees warmer, and yes it is more difficult to remove and replace a panel (Although on my previous camper we received 2.25 inch hail that took out all the neighborhood roofs, cars, siding, gutters, fridge and roof vents but the solar panels took the beating with no damage). The upside is an extremely clean installation which does not detract from the appearance of the motorhome, no leakage ever, lower wind resistance and reduced installation costs. Besides its great for stealth camping too and the silence of 60 amps of battery charging power is pretty much awesome and heavy overcast days still gives me 19-22 amps of charging

12 gage wire runs from each panel to a central connection box and then a short run of 4 gage wire down to the Morningstar MPPT Charge controller and then on to the batteries.

I have had multiple campers with this method of installation as well as others that have chosen the same method and after 8 years we have not had a single issue with a panel unbonding from the roof. Sometimes simpler is better.... (something I learned in an engineering class in college)

[SSG Scott]

Originally Posted by Possum

Can you point me to this information please? Google keeps giving me paid sites their algorithms think I want to read, not what I am asking for. At present I have a bunch of different sized units hooked in Parallel and with 8 gauge wiring running to the bus bar which leads down to the controller through 8 gauge wire and then on to the batteries via 6 gauge wire. It's been keeping all our batteries charged since last spring when I completed the wiring. TIA

In real life testing the figure you want to look at is the Vmp of the panels (Voltage max power). Ideally for max power transfer to your system you want them to be the same, but the real measurements show that it will work just fine, just try to keep the difference to less than 1 volt and preferably .5 volts. You will loose a little bit of power from the panels that have a higher Vmp.

I have a mix of 100 watt and 160 watt panels on my roof (part of maximizing roof coverage and avoiding shadows). Just add one more panel and that should more than make up for the efficiency losses. The biggest issue I see in systems is not using wiring big enough (voltage losses) and not understanding that just a shadow the size of the palm of your hand will drop the output of that panel usually by about 80%, so its super important to avoid shadows!