Advise on Solar Mounts ....

[LifeInsideJack]

We scored three 250w solar panels in exchange for some work. This is great as this is how we like to pay for things.

Before you get all jiggy on that I'll tell you that Cat is an Electrical Engineer that works for a solar company and we've both been in solar for over 9 years. We have the knowledge and experience of building farms and even smaller off-grid set ups.

The problem is that we haven't installed any on RVs.

What brackets have you used? What did you like? What do I need to be aware of?

Our RV, Jack, likes to go fast. He's easily pulling 75 on the freeways when that's reasonable. So that's a consideration also.

We are having the roof resealed next week and while they are up there they are going to attach the panels to the roof and seal the mounts.

I have to order mounts.

What am I purchasing?

[Almot]

Converting phone charger to 12V is easy, you can just get a $1 USB charger from Ebay that plugs into cig lighter receptacle.

Converting things like TV doesn't make much sense, modern LED TV draws very little power. 100W inverter will do - with remote switch, or make it accessible and turn it off when not in use.

12V fridge of modest 6-7 cu.ft size your solar could handle in summer, will be pushing the limits in winter - not gonna make it on some days, so you'll dip into your battery resources "deeper", and even 6 cu.ft model will be a costly affair.

12V A/C - have some doubts. Removing that much heat from the trailer to the outside requires a lot of energy - KWH, no matter in 12V or 110V.

[LifeInsideJack]

Almot wrote:
Yes, I noticed that small panel on the A/C.
In summer, and without controller, it could even over-charge a small battery if there are no parasitic loads, i.e. engine battery is disconnected from everything except for this panel. OTH, if there is anything drawing power while in storage, it might not be enough to keep the level of charge where it was.

I have a trickle charge mounted under the hood. The cord for it runs into the coach. It's easy to keep that going from inside.

Ultimately Cat wants to convert much of our stuff to 12v. That will involve purchasing 12v adapters for our laptops and electronics. Then we will look at replacing the fridge and eventually the A/C as there are more and more 12v A/C units hitting the market.

If we could get these devices in place we could unplug Jack. The eventual goal.

[Almot]

Yes, I noticed that small panel on the A/C.
In summer, and without controller, it could even over-charge a small battery if there are no parasitic loads, i.e. engine battery is disconnected from everything except for this panel. OTH, if there is anything drawing power while in storage, it might not be enough to keep the level of charge where it was.

[LifeInsideJack]

Almot wrote:

Joel_T wrote:
A/C? Looks like what ever you tied to it ran away with parts of it. 🙂

Shrouds are often made of inferior material. Either vinyl or lower-end fiberglass (not the kind used on average FG boat). After 3-4 years in the Southern sun it becomes brittle and cracks. Black color for roof A/C wasn't a good idea either.

Yeah, that thing has taken a beating. We added a shroud to the front vent. Not sure why it wasn't there. The guy moved the one from the bathroom up there so it would be black. Personally I want to replace all that stuff up there with nice new stuff and it will all be white. I think the previous owner's black fetish went just a bit too far.

There are new A/C shrouds in black at the supply store but I'm not sure I like them. The little solar panel on the shroud now isn't doing anything. It is supposed to be charging the engine battery. It isn't.

[RJsfishin]

Almot,...
Difficult to see, there is a threaded 1/4" x 1" x 3" alumunium flat bar pop riveted inside the frame at all 4 mounts of each panel.

I only add the tilt bars when wintering for a month or more in AZ, and the sun arc is low in the south.

I have had "nutserts" fail/spin in previous installs, therefore the more positive threaded flatbars riveted to the frame.

[Almot]

RJ, to be able to remove this thumb drive (or a regular bolt), there has to be a thread in the frame. I installed rivet-nuts into the frame, for this purpose. Stainless rivet-nut. The idea was to tilt the panel sometimes. Having abandoned this idea (too much trouble and there is no need to tilt, I harvest enough power already), if I were to do it again, I would rather used Z-brackets and avoided the rivet-nuts.

Unless you can get somehow into that 1" crack under the panel and attach/remove a regular lock-nut on the other side.

[RJsfishin]

[CJW8]

I used standard residential mounting hardware that you would use on an asphalt shingle roof. Hasn't been a problem.

[Crabbypatty]

I simply made my own by buying 1.5 inch aluminum angle from the hardware store and cut them into 1 inch lengths. 1 per corner and bolted them tot he panels, then screwed the panels to the roof using a glob of self sealing dicor. Rock solid no leaks servicable and inexpensive. If you want to spend the big money on moveable mounts thats up to you. I for one like the fixed mounts and its one less thing to do after setting up camp. I didnt want solar to become a chore. I fully recharge in the after noon with only 428 watts. Thats with three college kids, their devices, us, tv, as well as being really lazy and using the electric coffee pot. I have two Trojans t-125's and Mornings Star 45 with a trimeteric meter. What batteries are you considering?

[Almot]

Joel_T wrote:
A/C? Looks like what ever you tied to it ran away with parts of it. 🙂

Shrouds are often made of inferior material. Either vinyl or lower-end fiberglass (not the kind used on average FG boat). After 3-4 years in the Southern sun it becomes brittle and cracks. Black color for roof A/C wasn't a good idea either.

[Joel_T]

Yea, shade might prove to be a big enemy. Dunno. You have all the ingredients for a bunch of solar power though. Just keep an eye on how thing's are performing different times of the day and parked this way or that and at the same time contemplate ways to maybe tilt your way out of shade for those more demanding situations.

What happened to your A/C? Looks like what ever you tied to it ran away with parts of it. 🙂

[mrmomb]

westend wrote:

With the shading issues here it looks like only one panel is producing any real power, except for high noon. A tiny bit of shade will kill the entire panel output. Remember these are series devices. ALL wafers need to be in the sun.

[Almot]

Shading becomes important if this is MPPT with panels in series. May result in disproportional drop of total output. Less important in parallel wiring, where it always drops proportionally to the shaded area.

I don't think that 3*250W is overkill. It does rain in SoCal - yes, in desert. People there tend to camp in winter at least as often as in summer, if not more. On a winter day if it rains all day you'll barely harvest enough to keep battery where it was before, with only fridge and few lights running. Though in MH you probably have a generator.

Mounting... Can't be 99% positive at this angle, but a few things look not quite right:
Not enough sealant under the bracket. It should be oozing from under the perimeter, on all sides, overlapping the bracket area by 1/4-1/2 inch.
TAD small footprint of each bracket, too.

Also, it looks like they are L-brackets, not Z-brackets. If you will ever have to remove the panel for any reason, getting those fasteners out of the frame or reinstalling them again will be a royal pain. The only instance when this type of mount is OK is when you are using rivnuts in the panel frame, so there are no locknuts on the other side and bolts can be easily removed.

[LifeInsideJack]

Searching_Ut wrote:
The mounting looks good to me. Given your roof design, it appears you'll probably have shading issues on one or more of your panels during parts of the day depending of course on where and how you're parked. To maximize your daily energy harvest you'll want to make sure your wiring and controller is set up to account for that.

Yep. The reality is that this is a bit extreme for a motorhome. It's not like we're running a bunch of stuff in there at the same time. So the shading issue, although very real, isn't that much of a concern.

We have a 40* rule. That's not outdoor temperature, that distance from the Equator. We're desert people so the sunlight is amazing and typically (although not this year) we experience 310 days of sunshine per year. Staying out of the Frozen Tundra (41* or higher) will help the kit perform very well.

Cat, my girl, is the Electrical Genius putting this together. I'm confident that she will get this running very well.

The panels were in exchange for Rife Therapy.
The charge controller was a gift from on off-grid customer.
We came into some budget issues so the inverter is on-hold currently.
The batteries will be AGM and that will require a modification to a storage box. So the final bit will take a little longer to complete unfortunately.

Thanks !!