Boondocking an Air Conditioner

[DaveW]

Originally Posted by RocknRoll

I believe you may be hard pressed to get even 600W on the roof of a 2108FBS, especially if you plan to do any maintenance. Source the panels you want and take the measurements to the roof. Don't forget to give yourself some walking room.

A solar suitcase is usually 200W max unless you parallel multiple together.

The panel on it already is rated at 190 watts. I can certainly fit at least 4 of those on the roof, maybe 6, and there's room for wider panels. I can also put panels on the front and/or sides if I really want to. I don't need them all in the sun at the same time.

Yes, I plan on multiple suitcases if I go that route.

I'll make it work.

[DaveW]

Originally Posted by RocknRoll

I believe you may be hard pressed to get even 600W on the roof of a 2108FBS, especially if you plan to do any maintenance. Source the panels you want and take the measurements to the roof. Don't forget to give yourself some walking room.

A solar suitcase is usually 200W max unless you parallel multiple together.

This is what I have so far. I plan to use Renogy 175W flexible panels for weight reduction and they also do a better job of capturing energy at angles.

4 panels for 700W:


5 panels for 875W:


I don't think I can get much more than that on the roof. I'm likely going to add 2 more 175W panels to the front of the trailer. I'm also thinking of making my own lightweight solar suitcase for extra energy when needed.

I liked this idea for attaching them and intend to do something similar:

https://www.youtube.com/watch?v=hROYaqY83v4

The trailer dimensions were taken from blueprints. I expect the actual dimensions of the vents and A/C on the roof to be a few inches larger. It's been cold here and I haven't wanted to climb up there with a tape measure just yet...

I don't believe running the A/C while boondocking is going to be viable just yet. At least with a trailer this small.

[DaveW]

Nope, those layouts will not work. The A/C takes up a lot more space than I allocated. The panels will be too wide to fit on the sides of it. There are also some other features which are not on the blueprints I referenced. I can probably only fit 4 of these panels on the roof. But I may be able to fit a couple of lower wattage panels on there with those 4. I'll update when I have a concrete layout.

[RocknRoll]

Originally Posted by DaveW

I liked this idea for attaching them and intend to do something similar:

Tito is a clever guy. Not sure if you saw it, but he also posted a 1 year update

https://www.youtube.com/watch?v=enEH...Gf84A&index=11

[DaveW]

Yeah, the heads of his bolts weren't secured so they spun when he tried to loosen them. I planned to use elevator bolts, or something similar, not the type of bolts he used. But I may not have thought of that without seeing it first.

I may also make something custom since I have the resources available to me to make just about anything I want. I'm a master technician (aerospace machinist, not automotive). I can make stuff at work.

[MadMaxWinny]

Dave, I think you dismissed David a little too quickly. While battery technology has improved dramatically (and will continue to do so), solar has a ceiling. Current panel efficiency is on the order of 15-25%. This means that even a 100% efficient panel (discussed, but not likely any time soon) would only quadruple the output. This limit will always prohibit things like "solar cars" (Al Gore be damned). Solar has a place in low voltage systems. It just has practical limits. I think this is what David was leading to when he said "No free lunch."

Others have discussed the shear magnitude of charging capacity necessary to replenish 600+ Ahr. Most likely, the only realistic way to achieve this is with the genset/charger, or with the engine alternator. What people are trying to suggest to you is to cut out the middle man and run your genset for more efficient AC directly. I typically run mine for a couple of hours after the sun sets & then throw open the windows (humidity permitting). You sure would save a lot of money!

As my mentor was fond of saying 40 years ago: "Any time you want to heat or cool air or liquid, for any significant period of time, low voltage is rarely the answer."

There ain't no free lunch.

[puttin]

As my mentor was fond of saying 40 years ago: "Any time you want to heat or cool air or liquid, for any significant period of time, low voltage is rarely the answer."

-Worth remembering.

[moabdds]

Just a note on how much solar you need per battery. When I installed my system with 3 Battle Born batteries, the tech at Battle Born told me they recommended 250 watts of solar per 100 amp hour battery, so I would need 750 watts for the three batteries. I found a place in Phoenix that sold slightly used panels for a great price, so I put 4 250 watt panels on my 27' foot Itasca 27N motorhome. That gave me 250 watts of over-panelling, so I can add a fourth battery if I want, or just charge my three at a faster rate.

The panels I got were 4 or 5 years old, so should have only about 20 more years of life left on them. Since I am in my early 70's, I'm guessing they have more life left on them than I do on me! (At least usable life, for both them and me.) I paid $100 each for the four, instead of $400 each for new ones at the time. I've been running the system for 2 years now and it works like a charm.

As an aside, I divided the four panels into two banks with a 40 amp solar controller on each bank. I did that for two reasons. First, two 40 amp controllers cost less than a single 80 amp controller, and secondly, by dividing it into two banks, if I get some shading on one of the panels during the day, it only decreases the output on that bank instead of on all four panels. For example, if you have 36 cells on your panel, and only one of the 36 is shaded, according to Stanford University's research, that will decrease the output by 75% on all the panels in that bank!

Jon

Just my dos centavos worth.

[Wyatt]

You didn’t actually mean that did you?

“ and I need heat I'll install a small wood burning stove in the trailer.”

[DaveW]

Originally Posted by Wyatt

You didn’t actually mean that did you?

“ and I need heat I'll install a small wood burning stove in the trailer.”

How else are you going to get heat in a survival situation when there's no fuel? They make small wood burning stoves just for RVs. If it comes to that I will install one to stay warm. But I have no plans on installing one unless I have to. I'll have one on hand just in case.

Once you know for sure if you need one it will be too late to get one.

[tinglett]

Originally Posted by moabdds

I've been running the system for 2 years now and it works like a charm.

I see you have a battery monitor which, in my opinion, is absolutely essential for boondocking. Know thyself (or thy energy usage, anyway!). Based on your experience now, do you find 3 batteries were the right number for you? If solar generally replenishes your batteries, I'd assume on average you run them down to perhaps 50% or maybe a bit more?

I have 2 BB 100Ah batteries that get us barely through a full week. I'm considering adding one more for margin, rather than investing further in solar. We tend to camp in the woods with plenty of shade, which obviously doesn't help the solar situation. Perhaps in the future we'll be able to vacation longer, but will still need to deal with the water situation anyway so I still believe a week target will remain about right for us.

[DaveW]

Originally Posted by moabdds

Just a note on how much solar you need per battery. When I installed my system with 3 Battle Born batteries, the tech at Battle Born told me they recommended 250 watts of solar per 100 amp hour battery, so I would need 750 watts for the three batteries. I found a place in Phoenix that sold slightly used panels for a great price, so I put 4 250 watt panels on my 27' foot Itasca 27N motorhome. That gave me 250 watts of over-panelling, so I can add a fourth battery if I want, or just charge my three at a faster rate.

Thanks for the insight. I still don't have my system hashed out. But I already know that I'm going to have more battery AH than I'm going to be able to replenish with my solar setup. I don't intend to run the bank down much at all on a daily basis though, maybe down to 80%, which my solar setup should be able to replenish on an average day without a problem. I want the larger bank to prolong the life of the batteries by not having to discharge them as much while also giving me a large pool of AH to carry me through shady days.

As for the inverter, I don't need to run high wattage appliances from my outlets so I don't need a large inverter. I only planned on using the TV sometimes and some low wattage stuff, like fans. Maybe charge a laptop when needed. But I will need functional use of my outlets while on battery power. So an inverter will be required.

I'll have a portable solar array (suitcases) to give me a boost of solar when/if needed. I haven't decided how big of one yet (certainly 400W or more). But I'll probably make my own using flexible panels for weight reduction unless buying them like that is already an option (I haven't looked yet). I figure that I'll use 48v panels to allow me to place them farther away from the TT as needed without as significant loss of power as I would have with 12v panels.

As always, plans can change as I receive more information. Planning this stuff is half of the fun for me.

[DavidM]

Here are some rules of thumb for realistic solar amp hour output based on fixed, flat mounted panels:

Sunny, southern location like Phoenix in the summer: 40% of watt rating

Average summer location: 30% of watt rating

Winter location: 20% of watt rating

So if you have 250 watts of solar panels and you camp in the middle of the country in the summer, you should get .3 * 250 or 75 amp hours. That pretty much jives with Battleborn's recommendation of 250 watts of panels for each 100 Ah battery.

David

[DaveW]

Well, as I stated, my bank is going to be too large to have 250 watts per Ah. At 800 Ah I would need 2000 watts and it's not going to happen. That recommendation is a maximum recommendation, not a minimum. If anything, lower wattage charging is better for the batteries.

[lenore]

Great job on panel location, staying away from shadows...

[DaveW]

Originally Posted by lenore

Great job on panel location, staying away from shadows...

Awesome comment! Thanks for the constructive criticism!

I have to work with what I have. The only way to avoid all shadows would be to install a system much smaller which would be worse than having part of a panel in a shadow here and there. But you are clearly an expert and I would love to see your layout idea and the wattage of that layout.


This thread has put a sour taste in my mouth. I'm unsubscribing from it. /thread.

[creativepart]

Originally Posted by DaveW

This thread has put a sour taste in my mouth. I'm unsubscribing from it. /thread.

That's too bad. I for one was looking forward to how your plans worked out.

Forget all us old fuddy-duddies - you do you and best of luck to you.