Getting ready to do a cargo conversion..questions on power

[Jim Ragsdale]

I am going to do a cargo trailer conversion for my first rig.  I want it to be completely off grid capable for an indefinite time.  I'm thinking extra tanks in the truck bed for fresh water, gray and black water storage to extend my time out.

I am also a power hog.  As I don't plan on adding any shore power connections, I want to provide my power needs all with solar.  I plan on covering the 24 foot v nose cargo trailer with as many solar panels on the roof and sidewalls as I can to the tune of about 2000 watts. 

I also plan on using non-rv appliances as much as possible so I can simply go to Home Depot and buy a new one when one fails.  I lived in a 30 foot Dutchman fifth wheel (stationary) for five years.  I couldn't work on the fridge when it failed so put a household fridge on the outside covered porch.  So I plan on putting a 10 cu ft residential fridge in the trailer build.  I'm going to use two 5000 btu window AC units I can buy for $150 each in custom holders in the sides of the RV so I can simply swap out if one fails.  I'm even considering electric hot water heat so I don't use up propane.  

With all that said, I am confused about voltages.
I understand I can get 12v solar panels or use "House" solar panels at 120V.  Should I use 12, 24, 36, or 48 volt battery packs.  Should I have 120v lighting or 12v.  Should I rethink my fridge ect and use 12v power for them?  I'm at the designing stage here and I could use some help in how best to provide my immense power needs.  


So if you where going to design a system from scratch like me, what voltages would you want to use?

 

[highdesertranger]

before we get into the electrical side of things let me ask a question. are you planning on boondocking, driving off road? highdesertranger

 

[Jim Ragsdale]

before we get into the electrical side of things let me ask a question.  are you planning on boondocking,  driving off road?  highdesertranger

Yep.   Think about permanently being off grid on BLM land.  The goal is to have to go into "town" as little as possible.  I'm even thinking of using Tesla's powerwall for the battery bank.  I want to be as completely self contained as possible.  Think 4x4 truck and lifted trailer, composting toilet to eliminate black water tank, and routing AC condensate drain to fresh water tank.

 

[eDJ_]

Welcome to the CRVL Forums      

I know you will get some good answers to your questions here.

After reading your post, I would only suggest the A/C condensate be better routed to your gray water storage.

You need potable water that isn't potentially contaminated by the air being circulated through the evaporator coil.  I can't say what that could or would be,  but I wouldn't suggest drinking it.

 

[ganto]

Yep.   Think about permanently being off grid on BLM land.  The goal is to have to go into "town" as little as possible.  I'm even thinking of using Tesla's powerwall for the battery bank.  I want to be as completely self contained as possible.  Think 4x4 truck and lifted trailer, composting toilet to eliminate black water tank, and routing AC condensate drain to fresh water tank.

when i was looking at tesla's powerwall i couldn't justify the cost since it would take two of them to run a toaster.

 

[Reducto]

There's no shame in having a generator as a backup. Sometimes it's just going to be overcast and uncomfortably hot or cold for a week and solar won't be enough to keep everything running.

Panel voltage is independent from battery voltage. The controller takes whatever the panel gives out and adjusts it to match what your battery needs. Higher panel voltage is generally good because it means you can use a lower amp controller, but I'd focus on getting the most efficient (in terms of power/square inch) and cheapest panels then find a controller to match.

Most of us set up our batteries at 12v because it's easier to find electronics and we can charge directly off the alternator. Some go with 24v which has some advantages. If you run anything continuously off 120v AC it means your inverter will be draining your battery 24/7 and you'll have to make it up with extra solar and battery. Investing a little more in a more efficient top loading fridge instead of a dorm fridge may be worth it. Maybe it means driving to a post office once in a while to pick up a replacement. Occasional use items are fine to run off AC.

 

[tx2sturgis]

Wow...this sounds very ambitious....and really, it puts your 'rig' into the 'tiny house' category, and pretty much removes it from the 'RV' category.

On this forum most of us are used to thinking of our rigs as a vehicle AND an RV...for the most part, and that is pretty much how we go about composing an answer.

But your plan has little to do with being a 'cheap RV' and more like being an expensive, self contained solar powered tiny house on wheels. (thats a mouthful!)

So you will probably need to frame all of your questions, and filter the answers, accordingly.

That being said, there is a LOT of knowledge on this forum, regarding batteries and solar systems.

It really sounds like you have little need or desire for any 12 volt lighting or subsystems, so, I'm thinking you should concentrate on the 120v system, similar to the way a home builder might. Only thing is, yours can be moved like a park model RV or mobile home.

So I'm thinking your battery system should reflect this, and should be one of the higher voltages, for better conversion efficiencies and smaller wire gauges.

My only technical advise at this early stage would be to re-think the AC water recovery idea, since that water gets nasty with all the exposure to airborne dust and dissolved aluminum oxide, and is better used to help cool the condenser (using a slinger ring) as is done on many window units. A rain-recovery system might be a better way to go, depending on where you plan to boondock, of course.

Also, give some thought to a solar-thermal system on the roof, or deployed at the remote site on the ground, that's either water or hot-air based, these can be made or bought and would provide hot water, hot air, or both, without taxing the batteries at all, or very little.

I think you should also be looking at tiny house forums and off-grid housing forums, and gather information there too.

Not trying to run you off, to the contrary, I want to keep up with this and see how it comes along....

What a project....good luck with it!

 

[Spaceman Spiff]

Welcome and Wow, that is an ambitious and interesting project.

My first advice (if you haven't already) is to visit handybob's blog:  https://handybobsolar.wordpress.com
Especially the RV Battery Charging Puzzle.  He rants a lot, especially about Quartzite solar installers, but you can learn a lot from him.  He and his wife have lived off-grid on solar/LA batteries for years.

Second advice is to create an energy budget: add up all the energy consumption for the devices you are going to use to determine how much you are going to need to replace in a day.  That will determine the minimum solar (and other) input you will need.

If you are staying put for a while you might want to consider adding a wind turbine.  These will usually make energy when the sun isn't shining.

IMO your biggest problem with 120V home appliances is they are not designed to take a lot of jostling and vibration.

'nuff for now.  I will be watching with interest.

 -- Spiff

 

[highdesertranger]

ok if you are planning off road driving. IMO keep the sides of your vehicle and trailer free of breakable things like solar panels. if I had panels on the side of my vehicles I would have torn them apart. you WILL scratch the living hell out of the sides of your vehicle, you can't be afraid of this or you will not get very far of the pavement, in fact that's how you tell a true backcountry traveler and a vehicle that is a pavement princess. also some things like ladders on the sides is not a good idea. you will eventually get a rather large stick/branch between the ladder and the body, not good. highdesertranger

 

[Jim Ragsdale]

I had (past tense) this vision of being out for months at a time, but that's not practical and I am really just trying to be able to be off grid for probably too long a time.  I guess I'm thinking of moving to the moon instead of realizing I can go get more water in 30 minutes down the road.  I really have to better define my idea of how long I need to be self sufficient.  The 2 week BLM camping time limit may be a better place to start than with an unlimited time.  I doubt I could go longer than 2 weeks without a McDonald's Double Cheeseburger any way. I keep thinking of putting in the upfront costs so I can live for nothing once I get traveling. I'm over preparing and that's over the top.

I've also come to realize my power requirements are nuts.  As I go through the items, it would take 4000 watts of solar to keep all my stuff running at 2000 watts of demand and charge my batteries for night use.  And that assumes 12 hours of sun.  The idea of extra panels on the ground would work and instead of putting panels on the side, Or I could hinge them so they fold over onto the top when traveling and fold out like an awning when parked sort of like a moon lander.  A Honda 2000 generator would go a long way during peak loads.  I just hate the sound but it would solve the problem during peak usage.  

I have to use Lithium batteries for weight reduction and I found a guy in California that takes Tesla batteries, breaks them up into modules for smaller uses.  The voltages are pretty high and while that makes more sense in terms of wire size, the continual use of the inverter would be a big power draw especially at the total wattage I'm thinking.  

I was trying to reduce my propane use and need to refill the tank by limiting it to just the stove.  I was going to go with a Wynter chest compressor freezer and use it to make ice for the cooler but now I'm thinking a propane fridge freezer combo would be a way to cut the electricity requirement.  

The AC water recovery is a dumb idea.  The rainwater collection is an idea I've seen on sailing videos.  I've already decided a pretty serious water filtration system is important.  I like the solar heating idea. I haven't gotten far enough to get to that part yet though I did read about a diesel furnace/glycol system for heat and hot water.

I keep thinking of putting in the upfront costs so I can live for nothing once I get traveling.   I'm over preparing and that's over the top.

I do plan on being off off road. The thoughts about clean sides make all the sense in the world. I even considered putting rollers on the back end of the trailer. My first stop was going to be Loving County Texas which is the least populated county in the lower 48. One person per 10 sq miles so you get the idea.

I really appreciate your thoughts on this and I need to think more about being more mobile yet defining my off grid time, having less power need,  and living more simply.

 

[highdesertranger]

I tried to use a propane refer but instead of having to make ice runs I had to make propane runs. IMO use propane for heat and cooking, use 12v refer for food. I spent many years and wasted a lot of money trying to get around the price of a 12v refer. when I finally got one it was an eye opener if I only would have got one to begin with I would be many dollars ahead.

right now I can stay out 2 weeks without resupply, 3 if I stretch it. I am shooting for 1 month without resupply. out west here you need to go to a hub city to get good prices on food and fuel. in some areas hub cities are few and far between. highdesertranger

 

[Richard]

when i was looking at tesla's powerwall i couldn't justify the cost since it would take two of them to run a toaster.

I'm curious how you came to that conclusion. Looking at the specs, here's what I see:

Usable Capacity
13.5 kWh

Power
7kW peak / 5kW continuous

--from https://www.tesla.com/powerwall

I mean, maybe you've got a monster of a toaster?

 

[Jim Ragsdale]

I'm curious how you came to that conclusion. Looking at the specs, here's what I see:

Usable Capacity
13.5 kWh

Power
7kW peak / 5kW continuous

--from https://www.tesla.com/powerwall

I mean, maybe you've got a monster of a toaster?

I think I saw a quote somewhere of about $6k for one.

 

[Jim Ragsdale]

I tried to use a propane refer but instead of having to make ice runs I had to make propane runs.  IMO use propane for heat and cooking,  use 12v refer for food.  I spent many years and wasted a lot of money trying to get around the price of a 12v refer.  when I finally got one it was an eye opener if I only would have got one to begin with I would be many dollars ahead.

right now I can stay out 2 weeks without resupply,  3 if I stretch it.  I am shooting for 1 month without resupply.  out west here you need to go to a hub city to get good prices on food and fuel.  in some areas hub cities are few and far between.  highdesertranger

You have an example of my thought process.  If I could run it off solar, either 12v or 115v, then there woulldn't be associated runs into town.

 

[jimindenver]

Hi Jim. Welcome to the forum.

I can't tell you what and what not to do but I can tell you what I have dealt with and my rig can go a month in the boonies. In fact it can go down moderate jeep trails, has over 1300w of solar, multiple refrigerators/ freezers and some home based appliances. So as I discuss your plans I will reference how/why my rig is set up.

First it is a 25 ft travel trailer. It has many of the things I needed already and cost wise I could not come close to building it out of a cargo trailer for what I paid. It has a 3000 pound cargo capacity which is needed for all of the solar, batteries, water, food and general supplies and possessions it has to hold. It is also lifted and pulled by a 4x4, believe me it goes where others refuse to follow which is the whole point.

As for staying out a month, there are practical hurdles in doing so. I was originally going to add a 120v 3 ft mini fridge with a 1 ft freezer to my trailers 5 ft propane fridge/freezer. It had a very low draw as far as mini fridges go but I realized quickly that I didn't need more refrigerator space, I needed more freezer space to be able to stay out long term. Meat, vegies and dairy only last so long even chilled. Frozen they last a lot longer. I ended up adding a 12v Engel refrigerator/freezer but could have gone with a larger unit designed for off grid use with a 12v compressor. I do use my propane fridge but out of the devices that do use propane, it uses the least and last a long time between refills.

What it was worth making it so they ran off of solar uses a lot more than the fridge. Adding a electric element to the hot water heater saves the most. Using solar ovens instead of the propane oven comes in second and a two burner electric hotplate can run all day when the sun is out and the batteries never know it. Even small electric heaters can delay the running of the furnace on cool clear days. Unfortunately to use these items at night requires a lot of battery storage, then again I rarely do things with them at night. My quarter ton battery bank keeps the rig running over night and extends the time it can tolerate cloudy days in a more limited fashion without needing a generator. On those days I use more propane as expected.

I could put more solar up top if I were to rack the whole roof but with limited space for batteries it seems senseless. Batteries take up room and even if LiPo weigh less, they have the same footprint. They have to go somewhere, right. You have to have room for the rest of the stuff you will need. I did add a tilting 435w panel to my truck that can be 50 ft from the trailer and turned to follow the sun. It really adds to the roof system and allows for the trailer to be shaded at times.

Speaking of weight, enough water to last a month can weigh a lot. I carry 60 gallons but usually am required to move every two weeks. I can use 6 five gallon portable water jugs and a 25 gallon portable waste tank to extend my stays in places like Ehrenberg where they don't require you to move on so quickly. It's nice not having to move the trailer.

Another thing to consider staying out for a month is clothing. It gets dirty and while you can have a lot, it stinks when it is dirty. Eventually like food, water, propane, waste tanks and trash it has to be dealt with. Come to think of it, trash and black tanks reek pretty bad if not dealt with on a regular basis.

You mentioned a window A/C. I use a low draw 5000 BTU window shaker that draws 450w. It is a bit more than your basic 5000 BTU in cost but the most recent version only pulls 410w. That means my system can run two when the sun shines and has a better chance at running one at night. Finding things that use as little power as possible is a big part of my plan.

Even though I haven't needed a generator in 5 years I do keep a small one just in case. I don't wish to push my bank too far and damage it. It would be very expensive to replace when a little noise would keep it happy. It hasn't been cloudy long enough so far but one of these days.....

So what you are thinking is possible but there are things to be thought out and hurdles to be dealt with. I hope some of the things I have done help you or at least give you ideas on how to do it for yourself. I have been boondocking off and on for 30 years, preparing this trailer for six and putting it to the test since the first of the year. It's not the best way for everyone, just for me.

 

[Jim Ragsdale]

Hi Jim. Welcome to the forum.

I can't tell you what and what not to do but I can tell you what I have dealt with and my rig can go a month in the boonies. In fact it can go down moderate jeep trails, has over 1300w of solar, multiple refrigerators/ freezers and some home based appliances. So as I discuss your plans I will reference how/why my rig is set up.

First it is a 25 ft travel trailer. It has many of the things I needed already and cost wise I could not come close to building it out of a cargo trailer for what I paid. It has a 3000 pound cargo capacity which is needed for all of the solar, batteries, water, food and general supplies and possessions it has to hold. It is also lifted and pulled by a 4x4, believe me it goes where others refuse to follow which is the whole point.  

As for staying out a month, there are practical hurdles in doing so. I was originally going to add a 120v 3 ft mini fridge with a 1 ft freezer to my trailers 5 ft propane fridge/freezer. It had a very low draw as far as mini fridges go but I realized quickly that I didn't need more refrigerator space, I needed more freezer space to be able to stay out long term. Meat, vegies and dairy only last so long even chilled. Frozen they last a lot longer. I ended up adding a 12v Engel refrigerator/freezer but could have gone with a larger unit designed for off grid use with a 12v compressor. I do use my propane fridge but out of the devices that do use propane, it uses the least and last a long time between refills.

What it was worth making it so they ran off of solar uses a lot more than the fridge. Adding a electric element to the hot water heater saves the most. Using solar ovens instead of the propane oven comes in second and a two burner electric hotplate can run all day when the sun is out and the batteries never know it. Even small electric heaters can delay the running of the furnace on cool clear days. Unfortunately to use these items at night requires a lot of battery storage, then again I rarely do things with them at night. My quarter ton battery bank keeps the rig running over night and extends the time it can tolerate cloudy days in a more limited fashion without needing a generator. On those days I use more propane as expected.

I could put more solar up top if I were to rack the whole roof but with limited space for batteries it seems senseless. Batteries take up room and even if LiPo weigh less, they have the same footprint. They have to go somewhere, right. You have to have room for the rest of the stuff you will need. I did add a tilting 435w panel to my truck that can be 50 ft from the trailer and turned to follow the sun. It really adds to the roof system and allows for the trailer to be shaded at times.

Speaking of weight, enough water to last a month can weigh a lot. I carry 60 gallons but usually am required to move every two weeks. I can use 6 five gallon portable water jugs and a 25 gallon portable waste tank to extend my stays in places like Ehrenberg where they don't require you to move on so quickly. It's nice not having to move the trailer.

Another thing to consider staying out for a month is clothing. It gets dirty and while you can have a lot, it stinks when it is dirty. Eventually like food, water, propane, waste tanks and trash it has to be dealt with. Come to think of it, trash and black tanks reek pretty bad if not dealt with on a regular basis.

You mentioned a window A/C. I use a low draw 5000 BTU window shaker that draws 450w. It is a bit more than your basic 5000 BTU in cost but the most recent version only pulls 410w. That means my system can run two when the sun shines and has a better chance at running one at night. Finding things that use as little power as possible is a big part of my plan.

Even though I haven't needed a generator in 5 years I do keep a small one just in case. I don't wish to push my bank too far and damage it. It would be very expensive to replace when a little noise would keep it happy. It hasn't been cloudy long enough so far but one of these days.....

So what you are thinking is possible but there are things to be thought out and hurdles to be dealt with. I hope some of the things I have done help you or at least give you ideas on how to do it for yourself. I have been boondocking off and on for 30 years, preparing this trailer for six and putting it to the test since the first of the year. It's not the best way for everyone, just for me.

You are the man!   I thought I was the only crazy one to go this route.   I'm going to read and re-read your post over and over.  I would really like to see one of Bob's videos going over your rig!.  Your set up sounds exactly like what I have in mind.  Hope you won't mind more questions.

 

[jimindenver]

Questions are always welcome. Bob did some videos of my gear but he is behind in editing so I have no idea when he will post them.

 

[highdesertranger]

actually I heard through the grape vine that the hold up is Max won't sign a release. he is holding out for more treats. highdesertranger