Cargo conversion- ideal solar system to power AC?

[gooby]

Hi all. I am new to this stuff, so bare with me.

I have a 16' cargo trailer I have converted to live in. I am using shore power most of the time, but would like to travel the country and be able to utilize AC. I use a 5000 BTU window AC unit currently. I have some health issues that make me need the option for AC if indeed I can't get shore power and it is too hot out, at least for the sleeping hours.

My understanding is I have two options. Build a unit and place a bunch of LiPO4 batteries into a tongue box of the trailer, or buy a pre configured unit, such as a EcoFlow Delta Pro.

My needs are going to be fairly simple. AC unit(if the weather requires it), occasional laptop and phone charging, a fridge and an occasional use of something like a blender.

My understanding is there are advanced AC units now that work on 12v as well, such as this here: https://www.amazon.com/gp/product/B...c77113de91d8f59b931738ce30e6d#customerReviews

I would just get a $1k honda generator and be done with it but I hate gasoline smells and wouldn't be able to use it in all locations. I am willing to spend 5-6k to get this setup properly. Hopefully you all can guide me in the right direction and let me know if this is feasible. I really appreciate any input. Thanks

 

[Al D]

Skipping the generator is a good idea. It wouldn't work for AC without a softstart.

If you've got $5k+, you could certainly invest in a heavy duty LiFePO4 solar system.

A 5kBTU AC will probably use about 400W per hour of use, but I'm not sure if it's big enough for a 16' TT. Is the trailer insulated? Also, is the window unit going to be hanging outside the trailer or are you trying to be stealthy? Air flow to the back of the AC is critical.

I would suggest getting a bigger sized AC, maybe in the 8-12kBTU range depending on insulation of the TT. The power consumption of those will be around 1kW per hour of use.

The other loads you mentioned are mostly inductive and will require heavier duty equipment. I would suggest a 3kW pure sine wave inverter, at a minimum. You're looking at a 400-800 ah LiFePO4 battery at 24V to run the AC in the day and night. You need about 2kW-4kW of panels on the roof (so get the 400W household ones, not the dinky 100W or 200W ones).

This is assuming the use of the window unit AC for 16hours continuously during hot days and warm nights. The mini split you linked to will probably use less power over all. Also, this assumes you have access to 4 full hours of sun to recharge the batteries. Without an energy budget, this is the best you're going to estimate.

 

[Charleswgibbs]

Skipping the generator is a good idea. It wouldn't work for AC without a softstart.

It would have to be a pretty puny generator to be unable to power a 5000btu window unit even without a soft start. I was able to power one with an 1800w continuous rated Westinghouse, I'm assuming his thousand dollar Honda mentioned would be at least that powerful.

My understanding is I have two options. Build a unit and place a bunch of LiPO4 batteries into a tongue box of the trailer, or buy a pre configured unit, such as a EcoFlow Delta Pro.

It might be a good idea to keep the batteries in the conditioned space, they don't like high or low temps. I'm assuming a tongue box in the summer in full sun with batteries being charged/discharged would get pretty hot, and if it gets below freezing you'll need a battery heater to avoid damaging them. Plus being inside the trailer they will be closer to your charge controller and inverter, so shorter cable runs and less voltage drop.

If you don't like gasoline you can get a lot of duel fuel models that run on propane, or conversion kits for others.

Im doing something similar to you, I'm converting a 7x14 v nose and will be living in it full time. It will have a mini split for ac. No shore power. I can fit four 400w panels on the roof, for a total of 1600w. That's with every single inch occupied by panels. Even then I plan to have additional panels I can deploy once I get to a location and have a backup generator capable of powering my trailer while also charging the batteries (not the 1800w Westinghouse lol)

If your panels are flat on the roof you'll also loose some power compared to having them tilted, which makes the task of running ac on solar alone even harder.

 

[Al D]

Yea, sorry. I thought I read a 1kw Honda generator.

As for tilting the panels, you should consider the uplift while driving. Tilting panels after you park would be ideal, but installing them permanently tilted would probably cause more problems later down the line.

Speaking to the feasibility of this, I wouldn't think you could fit 10 panels on the 16' trailer. But that's in the ball park of what would be needed. So max out the panels and design the system based on that. If you have the ability to make an awning out of extra panels, you might get close to the amount you need. But that's very custom work so know what you're getting into.

 

[gooby]

Thanks for the help so far everyone. Here's pics of the trailer currently. 5k is too small indeed. It gets me to 62 degrees at night but during the day if the sun is beaming, it barely works. The insulation job sucks on the trailer. My main complaint. It's like 1/2 or 3/4 inch styrofoam board.

 

[Charleswgibbs]

Another thing to think about, all those big windows will effectively lower the r value of the entire wall. Single pane is usually less than r1 and even an inch of foam will be r5 so it's a big difference (I do insulation for a living)

It might be worth getting some foam board and cutting out some window covers to secure to the inside on hot days. I know it doesn't look all that great and you loose natural light but I bet you'd see a difference when it gets real hot out.

Nice trailer! Doesn't look like too much is built in yet either so now would be the time to add more insulation in the walls and ceiling if it's in the budget. Turn it into a giant yeti cooler

 

[gooby]

Another thing to think about, all those big windows will effectively lower the r value of the entire wall. Single pane is usually less than r1 and even an inch of foam will be r5 so it's a big difference (I do insulation for a living)

It might be worth getting some foam board and cutting out some window covers to secure to the inside on hot days. I know it doesn't look all that great and you loose natural light but I bet you'd see a difference when it gets real hot out.

Nice trailer! Doesn't look like too much is built in yet either so now would be the time to add more insulation in the walls and ceiling if it's in the budget. Turn it into a giant yeti cooler

Hi charles, yep, the windows get HOT. I've used my laser thermometer and got the walls at 88 in direct sun and the window at 135 degrees. Thus, I have affixed reflectix aluminum on the outside which keeps the temp way down. I will do a more permanent velcro option for both the interior and exterior depending on if I want them affixed inside or outside when sleeping or when I need privacy, or just when the sun is hitting the trailer.

Thanks! Yeah, it's only got a bed, fridge, storage in it for now. I'm parked in the backyard of my parents house. I do want to reinsulate it but it's a lot of work, beyond my abilities. I found one guy locally who quoted me $3000 to redo it. Seemed insane, so I haven't done it yet. But getting some nice full inch of the pink foam board would be nice. I think getting the XPS throughout the interior, filling all the gaps, since I know the current stuff in there is mostly EPS and it's not even filling the full 1" cavity of the walls. Random pieces of EPS, some XPS, most of it being half the size of the wall, huge gaps, it's really poorly done. I definitely want the 'least toxic' insulation, and EPS/XPS seem to be it for people with chemical allergies like myself.

Once that is handled, I want to put in an aluminum shower, a hot water heater, a port to connect a hose to the shower from the exterior, a sink, a desk for working. Then all I'll need is a 12v fridge, energy system and figure out the AC situation, if I'm doing a 12v split or whatnot. I love my trailer but it needs a lot of work to be sufficiently ready for the road. I really wanna get out of FL and travel to somewhere like the colorado mountains for a few months next year. I don't really care what it all costs at this point, I was gonna buy a $100k airstream but the prices were just absurd for what you were getting. I'm 20k into this trailer(it's 100% aluminum hence the price) so I figure another 10-15k in it I'll be still 1/3 the price of a commercial, decent quality trailer and it will be great for my environmental allergies. Lots of those commercial RV's bother me with all the construction chemicals.

 

[Al D]

What you (don't) spend in insulation will directly affect the cost of your solar system.

 

[gooby]

What you (don't) spend in insulation will directly affect the cost of your solar system.

So if I presume the majority of the trailer has 1/2 to 3/4 inch styrofoam board(it's pure styrofoam, the white stuff), and some of it has 1/2 inch of blue XPS board, getting it all redone with the full inch of XPS board should significantly improve the insulation factor even with the large windows? There are multi inch gaps in various places as well. I suspect the roof is a lot of the issue too, because when it rains the temps drop inside drastically and quick.

 

[OffGridInTheCity]

I recently converted a 7 x 14 cargo trailer -> camper. I used 1" foam board (R5) all around - ceiling, floor, sides, nooks/crannies, tailgate - complete. I run a 9000 BTU mini-split for heat/cool. It takes ~5kwh/24hrs of power to maintain 75F in milder temps (50F low / 90F hi). In extreme temps such as 25F low / 110Fhi this goes up to 15-20kwh/24hrs. The panels will produce ~6kwh/24hrs if in full sun.

I did a 48v @ 260ah battery (10kwh useable), 3000w MPP Solar 3048LV, 1200w solar panels on the roof flat. I can go ~36hrs with full service (cook, hot water, heat/cool, tv) for 2 if us with no external power / solar.

Number 1 suggestion is to insulate, insulate, insulate - if I had R15 or R20 I think my heat/cool power would be 30% of what it is now!!

Here's a pic with Honda es3000is charging us up on day 2. The problem with solar panels is camping seems to ALWAYS be in shade

 

[gooby]

I recently converted a 7 x 14 cargo trailer -> camper. I used 1" foam board (R5) all around - ceiling, floor, sides, nooks/crannies, tailgate - complete. I run a 9000 BTU mini-split for heat/cool. It takes ~5kwh/24hrs of power to maintain 75F in milder temps (50F low / 90F hi). In extreme temps such as 25F low / 110Fhi this goes up to 15-20kwh/24hrs. The panels will produce ~6kwh/24hrs if in full sun.

I did a 48v @ 260ah battery (10kwh useable), 3000w MPP Solar 3048LV, 1200w solar panels on the roof flat. I can go ~36hrs with full service (cook, hot water, heat/cool) fir 2 if us with no external power / solar.

Number 1 suggestion is to insulate, insulate, insulate - if I had R15 or R20 I think my heat/cool power would be 30% of what it is now!!

Here's a pic with Honda es3000is charging us up on day 2. The problem with solar panels is camping seems to ALWAYS be in shade
View attachment 109576

Great setup. I definitely wish I had 2 or 3" walls. I am stuck with 1" so r5 is the best I can do. I bet on average my trailer is like an R2 given the shoddy job. My floor is also not insulated.

 

[OffGridInTheCity]

My understanding is I have two options. Build a unit and place a bunch of LiPO4 batteries into a tongue box of the trailer, or buy a pre configured unit, such as a EcoFlow Delta Pro.

Converted my honda 3000 to propane. I also got a dual fuel 2300 Champion - easier to manipulate than the honda
1) You can put LifePo4 inside.
2) I included 2 x 30lb propane in a box (vented to outside) for the generators (and emergency heat). Gasoline (as you say) is messy!

Not saying you have to, just sharing that it's completely doable

My needs are going to be fairly simple. AC unit(if the weather requires it), occasional laptop and phone charging, a fridge and an occasional use of something like a blender.

We went 3000w / 120v (MPP Solar all-in-one) as the main system with a 120v -> 12vdc @ 80a transformer for the 12vdc. This powers the 12v stuff - including the Husky tongue jack no problem. We have 120v refrigerator, InSinkErator (instant hot water at the sink), microwave, hot plate, tv, etc etc.

My understanding is there are advanced AC units now that work on 12v as well, such as this here: https://www.amazon.com/gp/product/B...c77113de91d8f59b931738ce30e6d#customerReviews

See comment above. I know that some prefer 12vdc as the backbone and buy special appliances... I just found it easier to go 120v and have 12vdc subsystem.

I would just get a $1k honda generator and be done with it but I hate gasoline smells and wouldn't be able to use it in all locations. I am willing to spend 5-6k to get this setup properly. Hopefully you all can guide me in the right direction and let me know if this is feasible. I really appreciate any input. Thanks

I built (as you can see in the pic) for the Honda es3000is - but its HEAVY. Decided to go with less powerful Champion 2300 dual fuel as I can actually lift it / carry it outside instead of rolling it outside (cumbersome).

Great setup. I definitely wish I had 2 or 3" walls. I am stuck with 1" so r5 is the best I can do. I bet on average my trailer is like an R2 given the shoddy job. My floor is also not insulated.

Thanks for the kind words.
Insulating the floor (insulate, insulate, ...) will help. But of course its whatever your goals are etc and trailers NEVER get finished... it's perfectly OK to continue to work on it (and work on it, and work on it...)

 

[Vigo]

I would say not to talk yourself out of the insulation upgrade because A: I don't think it will be as hard as you think given that the trailer is currently almost empty, and B: because 'hate to break it to you' but the electrical side CAN be harder than that. Not that it has to be or guaranteed will be, but if you turn out to develop a slight addiction to DIY energy projects like a lot of us and build bigger more complicated systems later, eventually you'll be standing next to some complex electrical system you built and laugh about that time back when you didn't think you could add insulation to an empty box. Forcing yourself to get through it is just a stepping stone to the cooler things you'll do later.

The only downside to insulating it is the only easy way to do it is to insulate 'inwards' by adding a layer. The challenges would mostly be to 'trim out' your openings nicely like doors and windows, but screwing some foam board up and then a 'finish' layer like thin plywood/mdf/sheetrock over that, is not particularly hard. The hard part is making it 'nice'.

Anyway, i suspect unless you did a VERY good job adding insulation you'll want to upsize the AC unit. Luckily, it's a lot easier to enlarge holes than to shrink them! I switched out a 5kbtu window unit for an 8k Midea inverter-driven window unit in my bedroom. It uses less power on average when cooling load is low (it can 'throttle' down to ~2kbtu/hr), and cools more when the load is high (8k vs 5k). Mine has the U-channel in it for use in actual windows, but through-wall mounting it is nearly identical to a regular unit, if not a little better. You would basically cut the hole for the outside dimension of the unit, slide it in until the U-channel was about centered through your 1" wall, and then slide down 'filler' panels into the U-channel and screw them to the wall. You could stuff the space between them with insulation.

I'm not pushing that particular unit, but it's a good option as it comes in 10k and 12k sizes as well and even the 12k has a 'low enough low' that it would use less watts running than a 5k does, so it would still use less energy than a regular 5k some of the time. Another advantage is inverter-driven ACs don't have the large inrush current requirements of conventional units so you don't need as large of an inverter to get them started. Midea does make a version of the same unit WITHOUT the U-channel, in a 12k capacity and WITH a flow reverser valve so it can do some heat pump heating, and it's ~$280 at Costco if you can find it.

A small mini-split would be fine, although you'd have to just close back up the hole you've already got, and the smallest mini splits are still about 2x the cost of the Midea or other small inverter-driven window units. The advantage is they seem to do substantially better on heating as the inverter driven window units mostly do NOT do heat, or still heat with electric resistive heating elements vs actual reversed flow heat pump action. The one midea i mentioned is an exception. There may be others. Real mini-splits are more efficient in cooling too, but probably would make less difference there than adding the ~$400 price difference as $400 more of lithium batteries to your setup. Just my .02 on that.

It looks like you could fit 1000-1600w of solar on your roof. That will run a 12k AC on high, although you will probably drain your batts during cloud coverage. Luckily cooling load and shade are inversely proportional so there usually isn't a need to run AC on high when conditions are very cloudy anyway. The Midea units I mentioned go all the way down to 100-200watts running at low fan speeds once they've hit the target temp and are just maintaining it. I have seen my 8k hit 1000w, but usually doesn't go above 650 running on high when it is trying to cool down to the temp setpoint.

So using the equipment and conditions i'm familiar with, if you stuck an 8k Midea in there, you could get away with 1.5kw but preferably 2kw+ inverter, and could run it through the night on <3kwh of battery capacity. More would be better, but I have run my 8k midea and measured it's consumption so i know for a fact that at least the above statement is true, as a bare minimum setup.

 

[gooby]

I would say not to talk yourself out of the insulation upgrade because A: I don't think it will be as hard as you think given that the trailer is currently almost empty, and B: because 'hate to break it to you' but the electrical side CAN be harder than that. Not that it has to be or guaranteed will be, but if you turn out to develop a slight addiction to DIY energy projects like a lot of us and build bigger more complicated systems later, eventually you'll be standing next to some complex electrical system you built and laugh about that time back when you didn't think you could add insulation to an empty box. Forcing yourself to get through it is just a stepping stone to the cooler things you'll do later.

The only downside to insulating it is the only easy way to do it is to insulate 'inwards' by adding a layer. The challenges would mostly be to 'trim out' your openings nicely like doors and windows, but screwing some foam board up and then a 'finish' layer like thin plywood/mdf/sheetrock over that, is not particularly hard. The hard part is making it 'nice'.

Anyway, i suspect unless you did a VERY good job adding insulation you'll want to upsize the AC unit. Luckily, it's a lot easier to enlarge holes than to shrink them! I switched out a 5kbtu window unit for an 8k Midea inverter-driven window unit in my bedroom. It uses less power on average when cooling load is low (it can 'throttle' down to ~2kbtu/hr), and cools more when the load is high (8k vs 5k). Mine has the U-channel in it for use in actual windows, but through-wall mounting it is nearly identical to a regular unit, if not a little better. You would basically cut the hole for the outside dimension of the unit, slide it in until the U-channel was about centered through your 1" wall, and then slide down 'filler' panels into the U-channel and screw them to the wall. You could stuff the space between them with insulation.

I'm not pushing that particular unit, but it's a good option as it comes in 10k and 12k sizes as well and even the 12k has a 'low enough low' that it would use less watts running than a 5k does, so it would still use less energy than a regular 5k some of the time. Another advantage is inverter-driven ACs don't have the large inrush current requirements of conventional units so you don't need as large of an inverter to get them started. Midea does make a version of the same unit WITHOUT the U-channel, in a 12k capacity and WITH a flow reverser valve so it can do some heat pump heating, and it's ~$280 at Costco if you can find it.

A small mini-split would be fine, although you'd have to just close back up the hole you've already got, and the smallest mini splits are still about 2x the cost of the Midea or other small inverter-driven window units. The advantage is they seem to do substantially better on heating as the inverter driven window units mostly do NOT do heat, or still heat with electric resistive heating elements vs actual reversed flow heat pump action. The one midea i mentioned is an exception. There may be others. Real mini-splits are more efficient in cooling too, but probably would make less difference there than adding the ~$400 price difference as $400 more of lithium batteries to your setup. Just my .02 on that.

It looks like you could fit 1000-1600w of solar on your roof. That will run a 12k AC on high, although you will probably drain your batts during cloud coverage. Luckily cooling load and shade are inversely proportional so there usually isn't a need to run AC on high when conditions are very cloudy anyway. The Midea units I mentioned go all the way down to 100-200watts running at low fan speeds once they've hit the target temp and are just maintaining it. I have seen my 8k hit 1000w, but usually doesn't go above 650 running on high when it is trying to cool down to the temp setpoint.

So using the equipment and conditions i'm familiar with, if you stuck an 8k Midea in there, you could get away with 1.5kw but preferably 2kw+ inverter, and could run it through the night on <3kwh of battery capacity. More would be better, but I have run my 8k midea and measured it's consumption so i know for a fact that at least the above statement is true, as a bare minimum setup.

Definitely gonna look into this unit. The frame for the window unit will have to be cut out so given that all of these units have different dimensions, I need to have a good idea of what size I need.

Regarding the insulation, my entire interior of my trailer is screwed together. I ordered the trailer with screws and rivets, specifically so I could take it apart if I wanted. Unfortunately the manufacturer also used a LOT of silicon caulk to attach the interior aluminum panels. So I will need to not only unscrew the interior, which is not too bad, but also deal with every single seam covered in caulk that is stuck together. That is why I have hesitated and probably why the guy quoted me so high to do it. I tried removing just one panel and it was starting to bend due to the caulk/glue or whatever was used, so I got frustrated and stopped.

Great info overall, thanks for the suggestions.

 

[Vigo]

The caulk will do air sealing but ALSO prevent pops/rattles, and that may be the main reason why it was done. A lot of times floor boards in homes are 'glued down' with expanding foam or some other adhesive, even though they're also screwed down. In those cases the adhesive is preventing 'creaking' from minor movements/shifts between the two surfaces.

So i'm not surprised they did that, it probably got lost in translation that you were wanting ultimate serviceability and wanted to take the panels off.

You can add your own layer of 'interior paneling' on top of a new layer of insulation, but it does add cost and a small amount of weight.. the bigger issue is having to make it look as nice as what's already there. I understand your dilemma!

Here is the exact unit i bought:

https://www.amazon.com/Midea-Inverter-Conditioner-Flexibility-Installation/dp/B08677DCKN

Here is the 12k version without the U channel and WITH the flow reverser for 'heat pump heat'. I believe it's in-store only at this point as it used to be on their website and now it's not. However, there are comments on youtube videos and other websites suggesting it is still in stores. I haven't been in recently to verify..

midea 12k costco - Google Search

 

[Loadtoad]

I powered my 7x16 with solar. Documented it all here on my channel.

 

[bedpan]

Depending on what your are towing with a DC2DC converter can get you over the hump and you can skip the generator all together.
I am early in my 18' conversion but just finished a 2 week trip boondocking most nights and only have hydro to plug into one night out the 17 on the road. Driving a couple hours a day was generally enough to charge up my 300AH of 12V (3.6kW) batteries. After spending 3 nights at one lake we were down to 20%. I started up the truck for a couple hours and was back to close to 50% getting us by the last night.

For reference sake I am running a 1000W inverter with a apartment size fridge on it. Which is my main AC load. DC is my water pump, lights and some fans.

Long term I am looking at 3000W inverter that can run a mini split. Likely 24 or 48V at around 5kW. I will not be able to run the AC long but I figure I can run it for heat or cooling just to take the edge off. I doubt I would run it more then a couple hours.

 

[SunnyJim]

Here is the 12k version without the U channel and WITH the flow reverser for 'heat pump heat'. I believe it's in-store only at this point as it used to be on their website and now it's not. However, there are comments on youtube videos and other websites suggesting it is still in stores. I haven't been in recently to verify..

midea 12k costco - Google Search

I'm here in 2023 looking for any info on this "with heat" version of the Midea and I can't find it anywhere. I wonder what was wrong with this solution that it so quickly disappeared.

 

[Vigo]

The costco website makes it look like it is still available. It has never been regularly available through any other retailer as far as i can tell. I saw it available on Amazon very briefly but it was marked up to ~$450.

 

[SunnyJim]

The costco website makes it look like it is still available. It has never been regularly available through any other retailer as far as i can tell. I saw it available on Amazon very briefly but it was marked up to ~$450.

The costco page doesn't mention anything about heat.