Inverter wiring for solar

[mikegascon1]

I am still at the thinking stage for solar. If I were to install a solar setup up, I would definitely want to install an inverter so my AC would work. How does that get wired in? To the power box under the shower? I assume they come with detailed instructions? I am not an electrical whiz bang and this is stumping me. I assume I am over thinking it and it is straight forward. Right?
Thanks

2007 3124
Vancouver, WA (close to Portland, OR)

[Bill]

Mike -

I am not an expert, but you will hear from the experts shortly.

The short answer is that the solar panels charge your batteries, and the batteries send DC power to the inverter. The inverter converts the DC power from the batteries to AC power, which is then used to power up the appliances and outlets. The air conditioner uses a rather enormous amount of power, so unless you have a LOT of batteries and a LOT of panels, running the AC may not be feasible.

As a quick benchmark, it is barely possible to run the air conditioner from a 2000 watt generator. Do you envision having well over 2000 watts of panels?

And now, over to the experts !!

Bill

[Wavery]

Mike -

I am not an expert, but you will hear from the experts shortly.

The short answer is that the solar panels charge your batteries, and the batteries send DC power to the inverter. The inverter converts the DC power from the batteries to AC power, which is then used to power up the appliances and outlets. The air conditioner uses a rather enormous amount of power, so unless you have a LOT of batteries and a LOT of panels, running the AC may not be feasible.

As a quick benchmark, it is barely possible to run the air conditioner from a 2000 watt generator. Do you envision having well over 2000 watts of panels?

And now, over to the experts !!

Bill

Bill pretty well summed it all up. Running the AC from the inverter for more than 5-10 minutes a day is simply not feasible unless you cover every inch of the trailer with solar cells and spend $6K in lipo batteries..

Most of us that boondock run about 200W-400W of solar panels and 200-300AH of battery storage. Then we run a generator for the AC, microwave. A 2000-3000W (pure sine wave) inverter is practical on that size set-up for that 1st pot of coffee in the morning or running the microwave for 10 minutes or so.

[rickst29]

In general, the 12-VDC "12 volt" and "grounding" cables (between Inverter "input" and the battery terminals) need to be as short as possible, so that they do not consume power in wiring losses. If the Inverter is expected to run household appliances such as a coffee maker or microwave, those cables must also be very large. I use dual AWG 2/0 supply cables between my battery packs and my relatively big Inverter.

Although Solar power can contribute to the "12V" power draw on the batteries, the batteries themselves are the main source of power for an Inverter. The Solar system is wired to charge at the batteries (or their corresponding "bus" connectors, 12v and ground).

While the Solar system puts power into the battery bus terminals, the Inverter takes it away. The batteries themselves must provide any shortfall. If the Inverter is smaller than solar panels, or not being used for significant loads, then extra power remains to charge the batteries.
- - -
The most important questions, to ask you in return are: #1, how big are your batteries? and #2, what's the biggest appliance you hope to run?

[rich2468]

I am still at the thinking stage for solar. If I were to install a solar setup up, I would definitely want to install an inverter so my AC would work. How does that get wired in? To the power box under the shower? I assume they come with detailed instructions? I am not an electrical whiz bang and this is stumping me. I assume I am over thinking it and it is straight forward. Right?
Thanks

2007 3124
Vancouver, WA (close to Portland, OR)(Adding some clarity to what's already been shared by others)

Hi Mike- to accomplish what you've stated you'd like to accomplish (the ability to run the A/C from battery power) using off-the-shelf materials starting with an "average/factory" build TrailManor, you'd need around 100 Amp Hour of battery energy per each hour of A/C use- so if buying Battle Born (or other popular Lithium brands), think of needing one battery for each hour of A/C use.

To safely convert the Direct Charge 12 volt electricity from those batteries to 12 volt A/C you'll need an inverter (likely in the 3000 Watt size, to be safe).

To replenish the charge of your battery bank, while running the A/C at about the same rate that the A/C (running via Inverter) is discharging it; you'll need around 1200 Watts of solar cells.

The above configuration should, hypothetically, run a TrailManor A/C under perfect conditions...but it's almost never going to be "perfect conditions".

Tree cover, cloud cover, solar panel orientation, etc. will all impact solar charging.

There are multiple ways to attack inefficiency/ uncertainty of solar changing, but the most obvious are-
1. Minimize load demand (buy a more efficient A/C)
2. Increase battery bank size
3. Examine practicalities of pursuing your TrailManor running A/C on battery power and minimize (or abandon) expectations

You may be able to buy or build a battery bank of sufficient capacity to mitigate some of the cost (of purchasing name brand Lithium batteries), but there are still significant hurdles to accomplish what you've stated.

The basic design of a TrailManor, which is awesome for tow-ability, is not easily conducive to the desired results of running a stock A/C on battery.


For a background: I am halfway to being able to do what you've stated. I can presently run my A/C from my battery bank and 600 Watt solar array and am in the process of adding 400 more Watts and doubling my Lithium battery bank, so that I can have additional capacity.
-The extremely tricky part is balancing the ability to do that with the practical aspects of the TrailManor and its usability.

To address one of your immediate questions, the 120 Volt out of the Inverter needs to be wired into the 120 power side of the TrailManor's power converter to power the 120 volt plugs and loads. An auto switch-over device is used to ensure that the Inverter never powers that 120 volt side of the TrailManor's power converter when the TrailManor is hooked up to shore power. Search YouTube for "TrailManor solar" to find Matt Carver's channel (the Critter and the Butterfly) for an explanation and video of his installation of solar and that automatically switch-over device.



Rich

[Bill]

It occurs to me that when you said --

If I were to install a solar setup up, I would definitely want to install an inverter so my AC would work.
-- you might have meant the 120VAC Alternating Current distribution in the trailer (outlets), and not the Air Conditioner itself. If that is what you meant, I jumped the gun and got us off on the wrong discussion. It is always worth clarifying those terms.

Bill

[Bill]

To accomplish what you've stated you'd like to accomplish (the ability to run the A/C from battery power) ... To replenish the charge of your battery bank, while running the A/C at about the same rate that the A/C (running via Inverter) is discharging it; you'll need around 1200 Watts of solar cells.Rich -

I'm not sure where the 1200 watt figure comes from. In 2007, I think TM was using a Coleman Mach 13,500 BTU air conditioner, which seems to require at least 1800 watts when running. Adding a true-sine inverter efficiency of 85% (admittedly a SWAG) ups the ante to around 2100 watts.

I think I found the YouTube channel you mentioned, but although it is titled Solar and A.C. Upgrades, I can't find anything about the air conditioner. Are we on the same page?

All your other points seem spot-on.

No matter what, it is a lot of power.

Bill

[rich2468]

Rich -

I'm not sure where the 1200 watt figure comes from. In 2007, I think TM was using a Coleman Mach 13,500 BTU unit, which seems to require at least 1800 watts when running. Adding a true-sine inverter efficiency of 85% (admittedly a SWAG) ups the ante to around 2100 watts.

I think I found the YouTube channel you mentioned, but although it is titled Solar and A.C. Upgrades, I can't find anything about the air conditioner. Are we on the same page?

All your other points seem spot-on.

No matter what, it is a lot of power.

BillHi Bill,
That's first hand experience.

When watching my battery monitor live as I turn on and cycle through my 2021 2922KB's stock Air Conditioning running through my Inverter I see the following:

1180 Watts with the AC on high, 1020 Watts with AC on low, 197 Watts fan high, 131 Watts fan low.

The reading I'm seeing is straight from my battery bank (so Inverter losses are accounted for).

Matt Carver (YouTube the Critter and the Butterfly) just covers his Lithium upgrade and adding the auto switch-over. His Inverter is not large enough to run an A/C. Mine is; I have a 3000 Watt pure sine wave inverter.

[Wavery]

It occurs to me that when you said --


-- you might have meant the 120VAC Alternating Current distribution in the trailer (outlets), and not the Air Conditioner itself. If that is what you meant, I jumped the gun and got us off on the wrong discussion. It is always worth clarifying those terms.

Bill
I also assumed that's what you meant........:new_bdays

If you meant simply running a few 110V AC appliances (not the air conditioner), there are a few ways that they can be wired.


First, I will discuss hooking up your solar panels.

The solar panels can be mounted with solar "Z" brackets. Available on Amazon, eBay and most solar sellers websites. You can attach them to your roof with 1" wide, 3M VHB double side tape. No need to drill into your roof. Just be sure to clean all attaching surfaces thoroughly with rubbing alcohol. Attach the brackets to your panel(s) first. Do a dry run by laying the panel(s) in position on the roof and be sure that each one of the brackets lay flat on the roof panel. The rear brackets may need to be bent a little with vise grips or pliers to lay perfectly flat. Now attach the 3M VHB tape to all 4- brackets and carefully set the panels in place. Press down on each bracket (hard) for about 30-seconds) to activate the adhesive in the tape. Get it right the first time, there are no redo's. This attachment is actually stronger than using screws-

The solar panel(s) come with short pigtail wires that have MC4 connectors on them. That requires that you purchase solar wires (about 20') with MC4 connectors on one end. I prefer 8G wires but you can use 10G (a little small and less expensive) for up to 200W solar array. Those wires plug directly into your solar panel(s) pigtails with corresponding MC4 connectors already attached to your new wires. If you are installing multiple panels. You will need to buy MC4 "Y" connector pigtails. They are easy to use. Just ask if you are unsure.

Now, you are ready to mount your "Solar Controller". It is convenient to mount the controller on the back panel of the lower body of the trailer, next to the storage compartment door. That location is protected from weather and Sun, no matter if the trailer is open or closed. Just use S/S steel screws that usually come with the controller.

Now, plug in your MC4 solar wire connectors and run your solar wires across the roof to the driver side of the trailer and down the side (just in front of the widow and behind the upper roof bag seal when closed) then to the rear roof upper lift arm joint. You will need about an 18" loop at that joint before securing the cable to the top part and behind the lift arm. The loop is to allow for the roof raising and lowering. Secure wires , (I used plastic wire ties) about every 12" behind the roof lift arm, all the way to the lower lift arm pivot bracket. You will need to find a way to run the wire from that point to the controller. I drilled a hole in the bottom of the trailer entering the bottom of the storage compartment, in front of the battery box (back of the cabinet). I ran the wires into the battery box area, to the rear wall of the trailer where the controller was located. Then I drilled a hole about 4" below the controller (from the outside to the inside of the storage compartment). I ran my solar wires through the compartment, exited below the solar controller then cut the solar wire to length at about 6" outside the wall. DO NOT connect to the controller at this point.

You should have about 4' (or more) of solar wire left. That wire runs back through the hole that you made through the back wall (now you have 4 wires in that hole). As a side note......... everywhere that the wires pass through drilled holes, that wire must be protected from abrasion. I used short pieces of 1/2" PVC pipe and drilled my holes accordingly. Them I filled the PVC with calking.

The next step is to attach a 10G, "30A inline fuse" to the positive post of your battery(s). You will want to solder or crimp a 5/16" ring connector to the battery side of the inline fuse (pull the fuse out before connecting to the battery). Then connect the red solar wire to the other side of the inline fuse. It's preferable to solder but you can use a crimp style wire connector with heat shrink. Connect the black solar wire to the negative post of the battery. Run both wires out the drilled hole under the controller and hook them up the controller. The controller will be marked with + and - "Battery" symbol. Make sure your connections are tight, then put the 30A fuse into your newly installed inline fuse wire. Always be sure that the batteries are attached to the controller before making the connection to the controller from the solar array.

Now, you are ready to connect your red and black solar wires (from the solar array) to the controller. The controller will be marked with a solar panel symbol and a + and - connector.

Now you have your solar battery charger up and running to the batteries. Next, I will discuss hooking up the inverter if you found this helpful.

[Bill]

I'm not sure where the 1200 watt figure comes from.
Hi Bill,
That's first hand experience.
Interesting. I can't imagine that TM has downsized the BTU capacity of the air-co, so perhaps they have found a more efficient unit for new builds. The online specs just say "Low profile roof air conditioner", which isn't much help.

Bill

[rickst29]

(Adding some clarity to what's already been shared by others)

Hi Mike- to accomplish what you've stated you'd like to accomplish (the ability to run the A/C from battery power) using off-the-shelf materials starting with an "average/factory" build TrailManor, you'd need around 100 Amp Hour of battery energy per each hour of A/C use.

Rich
That 100Ah per hour figure seems a bit short, even for the new and MUCH more efficient TrailManor AC units, due to the "100Ah" battery pack BMS stopping discharge before 100Ah has actually been used. If we forget about lead-acid battery types and focus only on LFP, the following math will apply. (Lead acid batteries can't handle all the rotor-start current, and they can't be discharged as deep.) In this, which is mostly an addendum to your excellent post about your results with a new AC unit, I focus on the much worse situation with older models:

The average running watts of those older 13,500 BTU air conditioners is 1600-1800 watts while the compressor is running (depends on weather, and the condition of the AC compressor motor, and which model it actually is). The total capacity of each "100Ah" LFP battery, discharging from 100% full down to ZERO, would be around 1280 watt-hours, if such a battery could be discharged that far.

Discharging to 0% destroys LFP batteries. Their on-board "Battery Management Systems" will shut down before reaching zero, typically at only 10% left. But going that far down, on a frequent basis, would still hurt battery lifespan pretty badly. I don't go past about 20% left. I further reserve the first 100Ah of my batteries to run TM 12v loads and appliances (including a fridge) through the night and into mid-morning of the following day, when significant solar power again becomes available for recharging the batteries.

So, we have 80% maximum usable from 1280Ah nominal capacity, right around 1024 watt-hours per 100Ah. Conversion from 12.8-VDC to 120-VAC (in the inverter) consumes about 15% of that power, resulting in maybe about 850 watt-hours of 120-VAC power from each 100Ah of Lithium (LFP) battery. To run the older 13,500 BTU AC for one hour, with the compressor mostly "on", you would need around 1600 watt-hours. That's roughly 200Ah of LFP batteries, not just one.
- - -
In addition to the raw power consumed from the batteries, everything also needs to handle the extremely high extra "current load" which is required, for just a fraction of a second, to start the compressor motor. Each time the compressor turns "on" from an "off" State, the Coleman Mach 13,500 BTU compressor motor demands around 55 amps of current. (That's about 7000 watts). An Inverter smaller than "3500 continuous / 7000 peak" watts is unlikely to handle this "rotor start" loading, unless assisted by a high-quality "start-assist" device. With such a device handling "rotor start" peak loading, e.g. the 'SoftStartRV' (a load learning and really expensive one), you could get by with a somewhat smaller Inverter.

But not anything smaller than 3000/6000, because you'd be running at a high proportion of it's maximum continuous rated output. They're less efficient while being run that hard, and they burn out faster.

To feed a 3000/6000 Inverter, which will use more like 3500/7000 input watts at peak loading (because it is only around 85% efficient), you need "12VDC" wiring which provides a capability for more than 300 Amps. My own 2/0 wire pairs barely meet that requirement.

The costs add up, pretty fast. I know of only a 3 people who actually do this - JoeyCharismatic, Rich2468, and myself.

[rich2468]

Interesting. I can't imagine that TM has downsized the BTU capacity of the air-co, so perhaps they have found a more efficient unit for new builds. The online specs just say "Low profile roof air conditioner", which isn't much help.

BillI need to update my previous A/C load values reported.

I've realized that I had taken those in the evening, so it looks like my solar array was contributing to lower than expected numbers load numbers (despite it being well after 6 pm in March when I took those readings).

Here are my actual load numbers (today) with my breakers to the solar array switched off and 80 degrees Fahrenheit ambient temperature:

1350 Watts with the AC on high
1280 Watts with AC on low
187 Watts fan high
125 Watts fan low.

I do not see any major spikes to 1800 Watts through Victron Connect (when my A/C compressor kicks in) but am adding an A/C soft start as a proactive measure.

[Wavery]

I am still at the thinking stage for solar. If I were to install a solar setup up, I would definitely want to install an inverter so my AC would work. How does that get wired in? To the power box under the shower? I assume they come with detailed instructions? I am not an electrical whiz bang and this is stumping me. I assume I am over thinking it and it is straight forward. Right?
Thanks

2007 3124
Vancouver, WA (close to Portland, OR)

To address your original question:

Technically, the inverter is totally separate from the solar. All the solar does is "CHARGE" the batteries, that's IT.... nothing magic here.... just an expensive battery charger.. All the "inverter" does is convert your 12V DC battery power to 110V AC (until the battery goes to low voltage) Lots of magic going on there...
It's just the solar panel's job to keep the batteries from going to low voltage.

The amperage draw from the 12V battery to the 110V inverter is approximately 10x the demand from the appliance. In other words, a 10A appliance is run off of the inverter, the inverter will pull (approximately) 100A from your 12V battery (which is hopefully, actually at 13.2V or higher). This is an important and easy formula to keep in mind when thinking about running your 110V appliances on your inverter.

Knowing all this, helps you understand why the inverter MUST be installed as close as possible to the batteries. The cables from the batteries to the inverter must be large enough to handle 10x the load that the appliance itself is demanding. I used the 16" long, 2G wire from my 225AH batteries to my 2000W inverter (the cables came with the Powall inverter). I placed a 300A inline circuit breaker near the battery positive terminal to avoid problems from a short. DO NOT switch the circuit breaker to the "ON" position until both cables are connected. The negative cable can go straight from the inverter to the negative terminal on the battery. If you select a larger inverter, larger cables and circuit breaker must be used if you are going to have a larger load. The largest load that I have is a 900W (approx 10A) microwave oven.

Having said all that, now that your inverter is all ready to go, there are a few ways to get the 110V current from your inverter to your appliances. Some people simply run a 12G extension cord from the inverter to the appliance and forgo the complications of wiring it through the trailer's wiring all together. This is actually easy and very efficient. It may be the best way to go until you've done a couple trips to see how everything goes.

Other people simply plug the trailers 30A power cord directly into the inverter, thereby powering up everything in the trailer. However, if doing that, one should disable the campers "converter" or you will have the converter trying to charge the battery from the inverter which is quite inefficient. The Air Conditioner breaker should also be switched off.

Another way is to run romex (or other 14G stranded wire) from the inverter to the bus bar in the power panel of the converter. Again, the converter and A/C must be bypassed.

I chose to stay away from the converter altogether. I installed 3-dedicated 110V outlets in our trailer. One is located on the back of the bathroom wall, in the hallway. The 2nd is on top of the counter, next to the stove-top (next to the existing 110 outlet). The third is next to the existing outlets by the refrigerator. Each outlet is labeled "inverter" to avoid confusion. Running the 110V wiring through cabinets is pretty straight forward. I originally used 14G romex to run to the outlets but I just bought 3, 20' long 12G extension cords to replace the romex wiring for wiring my outlets. I didn't feel comfortable with the romex (that's just me).

By the way, I am quite impressed with the Powall 2000W pure sine wave inverter. I also purchased the remote control so that I could see the power reading (both 12V and 110V) from inside the trailer and I can turn the (very silent) inverter on/off from inside. Although, I now just leave it on as it draws about nearly 0W when at idle (as you can see in the second picture).

[mikegascon1]

To address your original question:

Technically, the inverter is totally separate from the solar. All the solar does is "CHARGE" the batteries. All the inverter does is convert your DC battery power to 110V AC (until the battery goes to low voltage). It's the solar panel's job to keep the batteries from going to low voltage.

The amperage draw from the 12V battery to the 110V inverter is approximately 10x the demand from the appliance. In other words, a 10A appliance is run off of the inverter, the inverter will pull (approximately) 100A from your 12V battery (which is hopefully, actually at 13.2V or higher). This is an important and easy formula to keep in mind when thinking about running your 110V appliances on your inverter.

Knowing all this, helps you understand why the inverter MUST be installed as close as possible to the batteries. The cables from the batteries to the inverter must be large enough to handle 10x the load that the appliance itself is demanding. I used the 16" long, 2G wire from my 225AH batteries to my 2000W inverter (the cables came with the Powall inverter). I placed a 300A inline circuit breaker near the battery positive terminal to avoid problems from a short. DO NOT switch the circuit breaker to the "ON" position until both cables are connected. The negative cable can go straight from the inverter to the negative terminal on the battery. If you select a larger inverter, larger cables and circuit breaker must be used if you are going to have a larger load. The largest load that I have is a 900W (approx 10A) microwave oven.

Having said all that, now that your inverter is all ready to go, there are a few ways to get the 110V current from your inverter to your appliances. Some people simply run a 12G extension cord from the inverter to the appliance and forgo the complications of wiring it through the trailer's wiring all together. This is actually easy and very efficient. It may be the best way to go until you've done a couple trips to see how everything goes.

Other people simply plug the trailers 30A power cord directly into the inverter, thereby powering up everything in the trailer. However, if doing that, one should disable the campers "converter" or you will have the converter trying to charge the battery from the inverter which is quite inefficient. The Air Conditioner breaker should also be switched off.

Another way is to run romex (or other 14G stranded wire) from the inverter to the bus bar in the power panel of the converter. Again, the converter and A/C must be bypassed.

I chose to stay away from the converter altogether. I installed 3-dedicated 110V outlets in our trailer. One is located on the back of the bathroom wall, in the hallway. The 2nd is on top of the counter, next to the stove-top (next to the existing 110 outlet). The third is next to the existing outlets by the refrigerator. Each outlet is labeled "inverter" to avoid confusion. Running the 110V wiring through cabinets is pretty straight forward. I originally used 14G romex to run to the outlets but I just bought 3, 20' long 12G extension cords to replace the romex wiring for wiring my outlets. I didn't feel comfortable with the romex (that's just me).

By the way, I am quite impressed with the Powall 2000W pure sine wave inverter. I also purchased the remote control so that I could see the power reading (both 12V and 110V) from inside the trailer and I can turn the (very silent) inverter on/off from inside. Although, I now just leave it on as it draws about nearly 0W when at idle (as you can see in the second picture).That is incredibly helpful. Thank you for the details.
In my original post, I said I wanted to figure out ac. I actually meant ac/DC. I will NOT plan on running my air conditioner from batteries. Sorry for the confusion.

2007 3124
Vancouver, WA (close to Portland, OR)

[Wavery]

In my original post, I said I wanted to figure out ac. I actually meant ac/DC. I will NOT plan on running my air conditioner from batteries. Sorry for the confusion.

2007 3124
Vancouver, WA (close to Portland, OR)You didn't create the confusion. We did that all on our own........ wait until you get a little old. Then you'll understand.:D

Did you see my post on the solar wiring?

[mikegascon1]

You didn't create the confusion. We did that all on our own........ wait until you get a little old. Then you'll understand.:D



Did you see my post on the solar wiring?I did see your post. Extremely helpful.
I have a 3124 and the battery is on the tongue. I plan to update to 2 6 volt golf cart batteries in the future.

It is new to me so, I am having a tough time estimating my needs.

Scenario 1 is the kids and I. I will need fans, or heat, television, recharge phones, interior and exterior lights. I would assume anywhere we go, I will look for hookups. It would be nice to have the option to boondocks though.

Scenario 2 is odd. Definitely no hookups. But less need for power also. I will be at fire camps that are 99% remote. In past years I only use my tent for sleep or maybe to sit for a short time after a shower to zone out. So, my power needs will be heat fan (and propane of course) and fans. Air conditioner would be awesome but not realistic. We usually work 16 hour days so not a lot of need for power consuming niceties.

If anyone has recommendations on low power consumption fans, that would be appreciated. One to move the air and one to blow on me at night. It is either hotter than heck or cold. No happy medium at camp. :-)

2007 3124
Vancouver, WA (close to Portland, OR)

[Kidkraz]

Mike, when I dry camp I bring several battery packs. I use a CPAP and depending on how long I'm out. I either bring a 299W pack or a 400W pack. I use the DC side of those batteries so they last longer than the AC side. Extra adapters required, but worth it.
I have several AA fairy lights with remotes, Goal Zero USB string lights, where you can add an extra light if needed.
Also several portable 26800 mAH batteries for the usb fan and lights. I use a 18v Ryobi fan with backup batteries and a smaller usb fan.
If your kids are old enough, give them a project to estimate how much power they/you need for electronics for a weekend.
I use a Mr Heater buddy when it gets colder, others have retro fitted their rigs with a Camco Wave heater.
Oh and scenario 2 is not odd, it's life.

[rickst29]

I did see your post. Extremely helpful.
I have a 3124 and the battery is on the tongue. I plan to update to 2 6 volt golf cart batteries in the future.

It is new to me so, I am having a tough time estimating my needs.

Scenario 1 is the kids and I. I will need fans, or heat, television, recharge phones, interior and exterior lights. I would assume anywhere we go, I will look for hookups. It would be nice to have the option to boondocks though.

Scenario 2 is odd. Definitely no hookups. But less need for power also. I will be at fire camps that are 99% remote. In past years I only use my tent for sleep or maybe to sit for a short time after a shower to zone out. So, my power needs will be heat fan (and propane of course) and fans. Air conditioner would be awesome but not realistic. We usually work 16 hour days so not a lot of need for power consuming niceties.

If anyone has recommendations on low power consumption fans, that would be appreciated. One to move the air and one to blow on me at night. It is either hotter than heck or cold. No happy medium at camp. :-)

2007 3124
Vancouver, WA (close to Portland, OR)
Let's focus on scenario two, with the first objective being a solar system which can recover your usage each day, if the sky isn't completely obliterated by smoke.

A 3124 has lots of surface area for panels, both front shell and back shell, but the lifting weight will be increased (by the weight of the panels). You could do a bunch of small 100w panels and wire them together, or you could go big, with just one (at most 2) residential-type panels.

As we speak, I'm discussing a new solar install with another TM owner up there in Washington State. He has a slightly smaller 2720, and can fit one of these residential-type panels on the rear shells. These are too large to be shipped from an Internet Seller, but many installers in USA are using them (including some in the Portland area) and some of those local home-installation companies will have some leftover panels from their "full-pallet" and larger truckloads purchases, which they can sell to you for a local pick-up.

Using newest PERC technology and built with a bit more durability, the Q-Peak DUO G10+ provides 385-400 nominal watts, but they're expensive. Efficiency ios the best in the business, at nearly 21%. These are widely used in residential roof installations, I have some of those on my own house (in Reno NV).

Using older technology, the 'REC Twinpeak 2' is only 18% efficient delivering 275-300 watts in a slightly larger area. But it has a much lower cost per watt. I've attached both of their data sheets, and the length of these panels does fit into TM trailer width.
- - -
Keep in mind that "nominal watts" are maximum power under "standard test conditions", which are so bright (and with such cool temps) that you will never EVER come close to that figure. The biggest factor in reduced performance, for a panel mounted flat on a TM roof, is the horizontal mounting. Even on June 21, the sun is never directly overhead at 90 degrees (due to latitude), and a "flat" panel gets less irradiance than the standard rating conditions. For long fire stays, you could consider using an adjustable mount. But that adds the trouble of climbing up there and adjusting the mount, which would be 1-2 feet inwards from the "long side" edge of the horizontal to vertical transition. The mounting would be more complex, adding more weight, and you'd need a ladder to get at it.

Summary hint: the most I ever get from my own "490 watts" of panels is about 420 watts, on a perfect day June day at 1pm daylight time. But from that, we also need to downgrade your panel output rating for the sunlight versus smoke conditions at a fire camp. They can be severe, leaving you with effectively no power at all. But even when the camp seems excellent, the haze has a big effect. As a wild guess, let me toss out a minimum of "800 rated watts" as the minimum panel configuration you should install for this usage. That would be at least one panel on each shell, running them in parallel to the solar charge controller.

In really bad smoke conditions, you will need to rely on a generator, or use a fairly high powered DC->DC converter through a separate pair of big wires, running from the truck to charge your TM batteries. The input current of those devices is large, too much for both the bargeman cable "Trailer battery Charge" and "ground return" wires. You'd need to size those cables according to the input current, being approximately like long jumper cables (but probably using Anderson connectors at both ends, rather than mere clamps). It's good for up to 660 watts nominal (and with a decent truck, that's darn near actual as well, rain or shine or dead-of-night). https://www.renogy.com/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/