Stuck In Solar Limbo

[PeteW]

Hello Out there,
So here's the thing. I'm a DIY solar newbie with some book and internet learn'n. I've done quite a bit of reading and youtube research (including Will's book), but I'm kind of stuck. Well, "Paralyzed" is probably a more accurate description. I'm also worried about all of the stocking / shipping problems. I'm not looking for the cheapest deal. I am looking for good brands and warranties. I'm also hoping to avoid to many time and money wasting Newbie mistakes. I think I'm especially in need of encouragement and advice. Here are my issues:

I'm stuck at deciding what solar panels I want to install. Some Background: I own an 1992 Airstream Trailer (tow behind). Roof space is limited and curved. At the moment I'm leaning toward rigid 100 watt panels such as the Rich brand. I'm referring to the mono-crystalline with the 45.5" x 20.5" frame size. Ideally I'd like to mount 6. That said, I'm certain I can mount 4 of this size, 6 might be difficult, so I'm also considering the Rich Poly-crystalline 39.6" x26.4" or a mix of both types. I'm planning to service a 400 watt LiFePO4 battery bank. With either a 2 or 3k hybrid inverter and an adaquate MPPT charge controller that would allow for some expansion if that need should arrive. I'm still hand wringing over this also. Plus now they have they all in one units. Ugh. I'm also struggling with whether it makes sense to go to a 24V DC system or just a 12V

Our 120V shore power is 30 Amp. This powered a single 15K rooftop AC (I'm replacing the old unit with a new Coleman 15K AC/HP and an Easy Start), 700W microwave, a couple of MaxAir Fans, LED lighting, etc. Naturally the solar is for extended boondocking capabilities and we don;t have planes to use the AC, but probably the microwave occasionally.. Everything is new as I'm doing a complete rebuild. I'd sure like some advice from those with some solar and RV experience. Here is a picture of the roof. Missing from this picture are a couple of plumbing vents that protrude from the roof along the left side. The square hole in the center of the roof is for the AC unit which will have a foot print of 41.5" x 28.5"

 

[jpcjtrtj]

What an exciting project . . . I have a 2005 International CCD which was in great shape when we bought it. I just upgraded converter (to four stage PD 4855), the battery (DIY 280 AH), added a DC-DC charge controller (40 amp renology) and a SCC (Victron 100/30). The photo below is installing the new battery, SCC and DC DC charger (which required removing most of the front couch . . . .) Comparing our rooftops, you have a boatload of space . . . My AS apparently came prewired for solar, but the wires are only 12 AWG and supposedly end just shy of the rooftop vent for the fridge. I have not yet jumped into putting solar on the roof. That may be next.

So far, I have stuck with ground based panels and a plug into the trailer. That allows me to orient them for best sun on the back of my truck (and park in the shade while still accessing solar). It is a bit of a pain transporting and setting up every time . . . Look at AM solar under their Airstream page for ideas. Also, LoLoHo just added a full solar system to their 25 footer (early 2000s I think) with AM Solar in Oregon. I seem to have seen a couple of pages where folks have added solar to their ASs. Do a google search. There's 3m tape you can use on the feet of the panels to avoid drilling holes and most builds I have seen use the chimney for the fridge (which I don't see on your roof . . . ) to bring the wires down into the cabin without adding another hole. Also, with the AS, be sure to only step on the frame (where the rivits go across the top; or you'll dent it or worse fall thru the very thin aluminum skin.

I can't speak to 12V or 24V, many here are fans of the 24V set up as it lowers your amperage and allows for smaller wires and larger inverters. I've also seen many recommending not to exceed 2000 watts for an inverter in a 12V system due to the high amperage. It's apparently easy to add a 24V to 12V converter for the stuff that has to run on 12 V; or if you are building from scratch you can set up your new electrical system at 24 V. I'd definitely go with as many panels as you can put on the roof. Six will not give you full output as they are flat; but you can wire in series and/parallel and keep your amps down and reduce your MPPT costs.

I bought two of the Rich solar panels and love them. They seem to outperform the newpowa ones i bought a couple years ago.

What's going on in the inside, I would love to see some photos.

Good luck.

 

[fratermus]

My two cents worth, given that I am just another random guy on the internet...

I'm referring to the mono-crystalline with the 45.5" x 20.5" frame size. Ideally I'd like to mount 6. That said, I'm certain I can mount 4 of this size, 6 might be difficult, so I'm also considering the Rich Poly-crystalline 39.6" x26.4" or a mix of both types.

Mono v. Poly is likely unimportant, although if they are running on the same controller I would stick to one or another so the panels are identical, spec-wise. If you need to mix them I'd run each type on its own controller for optimal performance.

I'm planning to service a 400 watt LiFePO4 battery bank.

400Ah maybe? 400Wh would be like a medium-sized Yeti and unlikely to run a microwave offgrid.

an adaquate MPPT charge controller that would allow for some expansion if that need should arrive.

A 40a MPPT (20A for 24v) will handle both 400w and 600w arrays. With 400w the controller would be slightly oversized (underutilized); with 6 panels on it it would be appropriately overpaneled (IMO).

I'm also struggling with whether it makes sense to go to a 24V DC system or just a 12V

With the limited DC loads (assuming microwave is the biggest) I think it's more a matter of preference than necessity either way. As @jpcjtrtj suggests, once you get to 2000w inverter loads the scales start to tip to 24v.

Roof space is limited and curved

Warning: half-baked daydream follows. At one point I was considering a pickup and a trailer type that was not amenable to Big Solar (A-liner). I toyed with the idea of maxxing out full-size truck rack on the tow vehicle

with the main battery bank in the bed, inverting it, and running a shore power line back to the trailer. It would allow me to put the trailer under a tree and leave power generation out in the sun. And would allow alternator charging while driving. Aesthetics weren't my concern, but panels on the tow vehicle would keep them from scarring that classic Airstream profile.

I'm sure it's a terrible idea for reasons I have not considered, but the "limited and curved" thing reminded me of it. Forget I ever mentioned it:

 

[jpcjtrtj]

@fratermus idea of the truck isn't crazy. Check this out:​

My Ford F150 Power Bank

Since I tend to trade up travel trailers often I figured why not have my power setup in my truck. Fords version it cute. But i hate generators and a truck idling is no better to me personally, when I boondock I seek silence. This is what I threw together last summer. Have since swapped out the...

diysolarforum.com

 

[PeteW]

jpcjtrtj and fratermus
Thank you both for your helpful feed back. Sorry, for the delayed response between my laptop sh**ing the bed yesterday and family visiting things have been hectic. I'm one finger typing this on a tablet. So despite my reply being short and late I'm very appreciative of your help.

I do have some good news. Day before yesterday my wife and I were able to measure things out on the roof and we determined we can fit 8 of the 100W mono-crystalline 45.5" x 20.5" panels up there and still have room for a modern TV antenna, a mobile phone antenna, etc. So, 800 watts of solar charging power.

That said, I was really happy for you bringing up portable panels and truck mounted systems, because it's also been my intention to do something like that for supplemental and shade related situations. i have do much more to say, but typing like this is just to frustratingly. More later and thanks again.

 

[fratermus]

I'm one finger typing this on a tablet.

That's frustrating. If the laptop outage lasts a while I've have good results with bluetooth keyboards for touchtyping.

bringing up portable panels... for supplemental and shade related situations

My main array is flatmounted on top of the van but I carry 2x 100w panels with me for challenging shade situations in forests. They are on 30' of extension and have their own controller. The tipping point for was 2 weeks in tall Oregon Pines when I couldn't hold Absorption for more than about 1.5hrs a day. Brutal. I swore to pick up some extra panels and I did when I saw they dropped to $73/ea at Home Depot.

I also lend them out to co-campers; one of them spent its time this week charging up a neighbor's "solar generator".

 

[chrisski]

If you have any intention of running the 15,000 BTU AC off solar, I think you need to go with 24 volts. Also for a microwave that’s used a lot, like 10+ minutes a day at 2 minute intervals, 24 volts is much better.

Trouble with 24 volts is everything else in your trailer is 12 volts, so you need some sort of DC to DC step down converter.

I have a 12 volts system with 5.3 KWh of lead acid batteries. I have a microwave I will run at two minute intervals 4 times a day. When I turn my microwave on it pulls 155 amps. To accommodate this, I have 4/0 wire and only run the microwave when the solar is producing 15+ amps of power to avoid the draw form the lead acid batteries. THe most power I’ve seen my 1350 watts of panels produce when I run the microwave is 74 amps.

Seeing 78 amps on the inverter at 24 volts would make me feel much more comfortable and use less than 4/0 wire. THe only down side to me going 24 volts would be I’f have to get a rather large DC converter to step down the voltage to run my trailer jacks that draw 50 amps.

 

[PeteW]

That's frustrating. If the laptop outage lasts a while I've have good results with bluetooth keyboards for touchtyping.

Good tip, definitely looking into one. I'll know more about the laptop on Monday or Tuesday. ?
If it's done or on the way out I'll probably get a new one, but the Bluetooth key pad is a really useful suggestion.

I also lend them out to co-campers; one of them spent its time this week charging up a neighbor's "solar generator".

That's very cool.

If you have any intention of running the 15,000 BTU AC off solar, I think you need to go with 24 volts. Also for a microwave that’s used a lot, like 10+ minutes a day at 2 minute intervals, 24 volts is much better.

So, if I did go to 24V, I could do that with 12V panels, right?

So far, I have stuck with ground based panels and a plug into the trailer.

I would love to see some pictures of this. Having thought of doing this in conjunction with my truck. I don't think I've seen something done with a nice plug connection. I'd like to hear and see what you can share on this.

I have seen use the chimney for the fridge (which I don't see on your roof . . . )

I forgot to mention that I'm going back with a 12v compressor driven RV frig. My OEM chimney was a mess, someone has really messed it up running solar wiring about 11 or 12 years ago. Anyway, since I'm doing away with the propane frig I got rid of the chimney and gained some roof real estate.

the battery (DIY 280 AH)

I'd like to hear more about this when you've got time.

 

[jpcjtrtj]

For my battery story, look here;

blmpow 3.2 280 AH cells

Ordered 4 on 3/25/21 on AliExpress; 550$ delivered to California. They arrived yesterday... tracking never budged. Packaging was solid; came with screws and decent bus bars (I’ll use studs). Cells looked good; no swelling; threads all good. 3 cells at 3.228 and one at 3.227. Started on...

diysolarforum.com

Surprisingly, I don’t have photos of the panels on my truck. Next time I set up; I’ll shoot a couple. Basically, I have a trifold canvas cover on the bed; in the morning, if it works out; I point the back of the truck at the sun and lean the panels in parallel against the top of the cab on top of the braces in the cover. I run a wire to to the input (which is now a ten foot #10 AWG pair with MC4 connectors connected to a Victron 100/30 SCC). At noon; I move the panels flat on the roof racks; in the afternoon; I tilt towards the setting sun.

 

[chrisski]

So, if I did go to 24V, I could do that with 12V panels, right?

There’s really no such thing as 12 volt panels. You have panels that output between 18 and 21 volts that match a SCC for a 12 volt battery. If you have those panels, you can put 2 of those in series for a total of 36 to 42 volts which matches a 24 volt system’s SCC.

Have you thought about getting Will Prowse’s book “Mobile Solar Power?” If you have Kindle unlimited, you can download at no extra cost. If you don’t, its around $7.

 

[PeteW]

Have you thought about getting Will Prowse’s book “Mobile Solar Power?”

Not that it's noticable, but I purchased and read Will's book (which is terrific and a bargain) nearly 2 years ago. It's not just that I'm a slow learner, I'm rebuilding an Airstream trailer from the ground up. It's been quite a challenge and I'm now at the point where I can really focus on the solar/ battery / inverter aspect so a lot of what I read has already leaked out and must be re-absorbed into the gray matter. Just as Will has continued to grow so has the knowledge base. It's pretty exciting really, but it's also stretching this old brain.

There’s really no such thing as 12 volt panels. You have panels that output between 18 and 21 volts that match a SCC for a 12 volt battery. If you have those panels, you can put 2 of those in series for a total of 36 to 42 volts which matches a 24 volt system’s SCC.

. And like you said I'll need a DC to DC step down converter. Ouch, my brain hurts.?

For my battery story, look here;

blmpow 3.2 280 AH cells

Ordered 4 on 3/25/21 on AliExpress; 550$ delivered to California. They arrived yesterday... tracking never budged. Packaging was solid; came with screws and decent bus bars (I’ll use studs). Cells looked good; no swelling; threads all good. 3 cells at 3.228 and one at 3.227. Started on...

diysolarforum.com

Wow, you're right in the middle of this, it appears. Did you get your BMS on AliExpress also? Man, I've got a lot to learn! Nice looking rig, btw.
You'd asked about interior shots of mine. Nothing to see yet other than a very nice Cossa subfloor.? I won't install the insulation and interior walls until I get all of my wiring completed. So far all of the work has been done to the frame, axels, wheels, tanks, subfloor and shell exterior. Once I get the solar in place (I'm going to fasten mine down, not just 3m tape). I think I'll be ready to finish the interior wiring and so forth.

 

[jpcjtrtj]

I bought the overkill solar 4s BMS

https://overkillsolar.com/product/bms-120a-4s-lifepo4/ I understand you can buy the base model a little cheaper thru Ali express, but I decided I would pay a little more for US quality control.

If I did it again, I would think about a 2p4s fortune cell pack for 200 AHs with two overkill BMSs ... easier to put together; seems a little more stable with the cases and rod system, and less haphazard on the quality than the EVE cell route and honestly 280 AH for my style of camping (no inverter; usually 5-7 days; some hookups) is probably too much ... we’ll see how it goes.

But, I had fun learning....

The last two days I redid the battery and added a little solar to my friend’s TAB camper and worked on the solar/battery for her 1954 vintage trailer. I got her to buy my 6 month old SLAs and all it cost was some wires, connectors and a little skin off my knuckles.

 

[PeteW]

---

If I did it again, I would think about a 2p4s fortune cell pack for 200 AHs with two overkill BMSs ... easier to put together; seems a little more stable with the cases and rod system, and less haphazard on the quality than the EVE cell route and honestly 280 AH for my style of camping (no inverter; usually 5-7 days; some hookups) is probably too much ... we’ll see how it goes.

Hahaha, how much seems always to be the dilemma. We lead a both different lifestyle. Before the rebuild we lived 7 to 9 months of the year in our airstream. Our goal is full-time. We've done a couple of power audits and it seems the 400 to 500 AH is good number for long term boondocking, 600 for us would be very comfortable. We're not big AC users while RVing but having the option for light usage would be nice. This my consideration of additional solar panels on our truck.

Where did you get your best information for battery building, balancing, etc. I need to build my understanding and confidence.

 

[PeteW]

The last two days I redid the battery

I'll check your thread, I hope that came out more to your liking. These this is definitely an area of interest for me.

 

[jpcjtrtj]

‘Redid the battery’ means replacing the standard group 24 battery on her Tab camper with two group 27s wired in parallel; adding a solar charge controller and hooking it up so she could plug in a 100 watt solar panel, plus giving her a plug for easy access for a trickle charger...mostly running wiring, crimping and logistics ...

To do this Airstream project, i started with some basic electronics knowledge from some classes I took as a kid, and a physics degree. I watched almost every video Will put out plus read his write ups on his web site and his book. I reviewed the Overkill solar BMS manual which has basic assembly directions and detailed instructions on top balancing. I read a ton of posts on this website, watched the airstream install videos on AM Solar and reviewed their wiring diagrams. I asked a couple technical questions to the AM Solar folks and posted a few on here. I watched the Long Long Honeymoon solar install, plus looked at the explorist website, videos, and wiring diagrams. I spent a lot of nights reading the various posts on here about fuses, compression, Rv installs, DC DC chargers and small solar chargers. Finally, I built a suitcase generator around a 60 ah LIPO battery and a second small project with a 25 AH battery pack and cigarette lighter socket for my CPAP machine. I added a shunt a month or so ago which required taking the front furniture apart. Then I dove in and made the battery and installed it last weekend. So far it’s running with a 4 mV delta between the cells.

 

[jpcjtrtj]

For this camper, I started out with a harbor freight kit; quickly realized it was not gonna cut the mustard and graduated to better panels and solar chargers (I shorted two in the process...) This was the next logical step in the progression as I have wanted to go LIPO4 for quite some time.

 

[Boondock Saint]

It all adds up and it all gets expensive, however it's better to be in solar limbo than solar purgatory having made the wrong decisions.

"Bless me father for I have . . . no clue as to what to do"

 

[PeteW]

got her to buy my 6 month old SLAs

So, I've tried to look up and figure out this acronym, no luck, what's it stand for?

plus giving her a plug for easy access for a trickle charger.

What type of plug are you referring to? Links, pictures? The reason I ask is I'd like to install some kind of attractive receptacle in the outside skin of the airstream for supplemental solar. No idea what that looks like or what to search for.

i started with some basic electronics knowledge from some classes I took as a kid, and a physics degree.

So, I have years of experience in the construction industry. Most of my electrical experience is with standard two phase 240v - 120v service. My brother in law is a master electrician. I also understand 12v but have far less hands on experience with it. Electricity and electronics have always been one of my diverse interests. I found Will Prowse about 2 years ago and promptly purchased and read his book. I'm actually rereading it now. I've also watched s number of this videos, but I had so many things I was learning to repair my frame and shell (we did a shell off) I've tended to absorb mostly what was needed at the time to complete the tasks at hand. I need to go back and watch more of Wills videos. I also, like Nate's videos on Explorist Life. I've followed Lolol, but haven't seen the solar install, I'll find it and check it out. If you're able please provide me links to some of the DIYSolar threads you think would be helpful. Really I'll appreciate any links you think are helpful. ?

 

[PeteW]

"Bless me father for I have . . . no clue as to what to do"

Hahaha, my personal mantra!

 

[PeteW]

Accidental repost