Off Grid Solar Design! I'd love your $0.02 Here.

[Chram]

My wife and I are building out our first skoolie and are intending to spend a year or two traveling the country with remote jobs. Super excited!

Here is the info on the bus:
2004 International FE300 DT466. 35' long. Roof raised 16". Keeping most if not all of the bus windows, but covering and insulating some. R6 subfloor and spray foam walls and ceiling.

We are right at the stage where we need to make some big decisions on the electrical system and solar setup. I'm a home builder and she's a HS science teacher, so we're not total dummies, but by no means are we electricians, and we want to make sure we get this right.
That said, we have gotten a decent idea of our power needs, so we have a loose framework and could use help figuring out exactly what components, sizes, and ratings we need to work with when it comes to the battery bank, solar array, gauge wires, MPPT, and inverter.

As for usage, we're wanting to be able to live off grid as best we can for as long as we can, and we would love to have the ability to run AC on sunny days, and possibly light AC through the night on eco mode. The Pioneer mini split we're looking at (12,000 BTU) will pull 800-900 watts continuous with a slow start, and the Pioneer rep we talked with recommended at least 1,200 watts of solar.
Here are the major appliances, and you can imagine all of the other small things like charging phones, laptops, etc. If we're boondocking, we would be pretty economical with most of the following (ie the wife probably won't be running a hair straightener as much in the woods).
We will have a generator (any tips on size / brand?), and aren't against running it to assist, but I'd love for the solar to run independent most of the time so that we're not constantly running through gas and worried about it being filled up.
-Minisplit (19 or 21.5 SEER? - 115V or 230V?)
-Refrigerator (modest size - undecided on power source)
-Microwave
-Hair dryer
-Straightener
-Toaster
-Disc lights throughout bus
-TV / DVD / chrome cast
-Maxfan
-Weboost
-2 laptops (remote work)
-Water heater
-Water pump

Here's what we're leaning toward:
24V system
1920 Watts solar (Renogy 320x6 mono)
412 ah batteries (SOK 206x2 in series)
3000VA 24V 70A Victron Multiplus (will this be enough?)
Cerbo GX battery monitoring
Victron Smart Solar MPPT 150/60 (need to go bigger? Oversized with 24V system?)
Victron Lynx Distributer


Beyond those^, I really don't know much about sizing things like wires, lugs, etc.
I also would love tips on what could run straight off of 24V DC, what would need a 12V step down, and what would be better on the AC through the inverter.
Is victron worth it? IMO, if I'm already spending a bunch of money, I'm okay spending a little more for parts that will be more efficient and reliable. We're all about value here.

As for the system, I'd love your thoughts / tips on how to make this system run as efficiently and *cost efficiently* as possible for our needs.
Thanks in advance!

[john61ct]

Inverter generator is required, along with say 30-50gal tanks for fuel.

Honda EU2200i is excellent, then if more wattage needed add a Companion version.

Put as many solar panels as you can possibly fit right from the start

Go with LFP, say a small 400Ah bank, the solar side will help reduce the genset runtime / noise / fuel expense.

Over time, add another 400Ah set if you find it will reduce the gennie usage even more, a worthwhile investment.

Just don't expect to get to solar-only, with those thirsty loads you will always need the genset inputs even if they end up being only 20% of the total energy used.

[Chram]

Here are some estimates for the loads of different appliances we are thinking about!

Refrigerator = 200 watts, 24 hours / Day
AC = 800 watts, 6 hours / Day
Toaster = 1,000, 2 minutes / Day
Hair Dryer = 1,200 watts, 2 minutes / Day
Hair Straightener= 350 watts, 1 minute / Day
Microwave = 1,000 watts, 6 minutes / Day
Water Pump = 150 watts, 1 hour / Day
Water Heater = 40 watts, 24 hours / Day (propane)
Disc Lights = 15 watts ea, 6 hours / Day x12
TV = 100 watts, 2 hours / Day
Charging misc equipment = 100 watts, 4 hours / Day

[Chram]

Originally Posted by john61ct

Inverter generator is required, along with say 30-50gal tanks for fuel.

Honda EU2200i is excellent, then if more wattage needed add a Companion version.

Put as many solar panels as you can possibly fit right from the start

Go with LFP, say a small 400Ah bank, the solar side will help reduce the genset runtime / noise / fuel expense.

Over time, add another 400Ah set if you find it will reduce the gennie usage even more, a worthwhile investment.

Just don't expect to get to solar-only, with those thirsty loads you will always need the genset inputs even if they end up being only 20% of the total energy used.

We are definitely doing LFP batteries, and would love to add more eventually. Thanks for the input! Do you think extra solar is worth it (financially) for how much it takes off of the generator?

[john61ct]

Absolutely, ROI would be well under a year, even months if fulltiming.

Burning petrol for hours every day gets expensive

as does, packing up and driving into town if that's the consumable that runs out first.

The ROI on the LFP storage required to run aircon is much slower but that is used by both the solar and the genset. Only benefit it has with the former is reducing the **frequency** you need to crank it up, not the total runtime in hours per day.

It's the panels (and maybe alternator setup) that reduces that.

So, if you were going to skimp on solar, then you don't need lots of storage save a lot of costs there, just run the gennie whenever aircon or other big loads are needed, use the stored energy to only feed the rest.

Personally, I would just move locations when it gets hot, follow the 60°s,

IMO whole point of being mobile.

[rffffffff]

I agree with avoiding hot places with a Skoolie but it's not always that easy... regardless of that I would really think about as much solar as you can fit up there. It's way easier to not have to worry about cloudy days or rain and generators and all of that mess. Flat panels will almost never reach full rated wattage and in some places, particularly in winter they really suffer, so 1920W may be more like 1000 or less at times. You won't regret more panels ever, there's no downside other than cost and I think that's limited stress for most relative to gas for the generator and dealing with rainy days and changing generator oil every 100 hours, etc. It makes for a much easier and simpler life in Skoolie land, which is usually not an easy and simple life.

[shaymcquaid]

Did a huge solar set up (3200 watts on roof 13k+kwh bank) Twin MPP2424LV's trying to run 1 of 2 Mini splits at a time in off peak solar hours is a disappointing pita at least in these last 2 N.Texas summers


What I'll recommend is a 50amp hook up



IMO:
*The Victron stuff is nice but not necessary.
*You will almost never get full panel potential.
*Cover your roof and work backwards from there. (Match your system to the panels in other words)
*Running A/C off solar is a very expensive proposition. (Depending on your insulation situation, could very well be impractical.)

-YMMV

[jofred99]

Just judging from my home setup, you will get approximately 65% of the rated power from your solar panels. Putting as much power as you can fit will definitely be a plus for future use.


Based in Arkansas, our largest loads are for freezers and refrigeration. We are running 3660 watts into a 48v 560ah lifepo4 battery bank. With a 12000 btu a/c and freezers on that bank we never got below 70% capacity and batteries were charged full again by 9:30 am on sunny days.


For our 8 window TC2000, I am going to squeeze (6) 400+ watt panels on the roof. The battery bank will be 48v at 280ah lifepo4. Loads will be a 12v Sun Frost ref/freezer, 12v LED lighting and a 12000 btu ac (31 seer). We expect to use about 50-60% of capacity daily, based on 5-6 hour a/c usage.

[LargeMargeInBaja]

For your photovoltaic, how are you mounting your rack?
.
Although a search of this forum will show a lot of different racks -- some 'nice', some cobbled from hack-sawed bed-frames and wishes -- please, attach your rack using substantial hardware into major frame components on the foundational vehicle.
Nobody wants to help you gather your favorite rack after it unplugs from the system and is strewn hither and yon after a disheartening bump at some inappropriate time.
.
Well, I probably should temper that 'nobody wants to help you with your rack' with a 'hardly'.
(Any grammarians in the audience?
Is 'hardly nobody' good?)

[john61ct]

no

hardly anyone

almost no one

[Rock-N-Ruth]

Originally Posted by Chram

My wife and I are building out our first skoolie and are intending to spend a year or two traveling the country with remote jobs. Super excited!

Here is the info on the bus:
2004 International FE300 DT466. 35' long. Roof raised 16". Keeping most if not all of the bus windows, but covering and insulating some. R6 subfloor and spray foam walls and ceiling.

We are right at the stage where we need to make some big decisions on the electrical system and solar setup. I'm a home builder and she's a HS science teacher, so we're not total dummies, but by no means are we electricians, and we want to make sure we get this right.
That said, we have gotten a decent idea of our power needs, so we have a loose framework and could use help figuring out exactly what components, sizes, and ratings we need to work with when it comes to the battery bank, solar array, gauge wires, MPPT, and inverter.

As for usage, we're wanting to be able to live off grid as best we can for as long as we can, and we would love to have the ability to run AC on sunny days, and possibly light AC through the night on eco mode. The Pioneer mini split we're looking at (12,000 BTU) will pull 800-900 watts continuous with a slow start, and the Pioneer rep we talked with recommended at least 1,200 watts of solar.
Here are the major appliances, and you can imagine all of the other small things like charging phones, laptops, etc. If we're boondocking, we would be pretty economical with most of the following (ie the wife probably won't be running a hair straightener as much in the woods).
We will have a generator (any tips on size / brand?), and aren't against running it to assist, but I'd love for the solar to run independent most of the time so that we're not constantly running through gas and worried about it being filled up.
-Minisplit (19 or 21.5 SEER? - 115V or 230V?)
-Refrigerator (modest size - undecided on power source)
-Microwave
-Hair dryer
-Straightener
-Toaster
-Disc lights throughout bus
-TV / DVD / chrome cast
-Maxfan
-Weboost
-2 laptops (remote work)
-Water heater
-Water pump

Here's what we're leaning toward:
24V system
1920 Watts solar (Renogy 320x6 mono)
412 ah batteries (SOK 206x2 in series)
3000VA 24V 70A Victron Multiplus (will this be enough?)
Cerbo GX battery monitoring
Victron Smart Solar MPPT 150/60 (need to go bigger? Oversized with 24V system?)
Victron Lynx Distributer


Beyond those^, I really don't know much about sizing things like wires, lugs, etc.
I also would love tips on what could run straight off of 24V DC, what would need a 12V step down, and what would be better on the AC through the inverter.
Is victron worth it? IMO, if I'm already spending a bunch of money, I'm okay spending a little more for parts that will be more efficient and reliable. We're all about value here.

As for the system, I'd love your thoughts / tips on how to make this system run as efficiently and *cost efficiently* as possible for our needs.
Thanks in advance!

Ruth and I full time in Sw. New Mexico. Our 40' Amtrans is heated and cooled with a 12000BTU pioneer mini split. We have a 7.5 cu ft deep freeze, two 4.5 cu ft refrigerators, one 60qt compressor cooler, 50" tv, laptops, cell phone chargers, microwave, instant pot, fans, toaster oven, and lots of lights. I also run an oxygen concentrator all night long.
We rarely have to fire the generator. Only after several overcast days when the temps are still in the 90s.

Our system is 24v. We have 6BYD 24v 200ah liFeP04 batteries in a 6P configuration. We would love to have two more. On the roof we have three four panel arrays made up of four 327W Sunpower mono panels, for a total of 12 panels. We get between 3600w and 4100w most days in good sun.

Each array is controlled by a 60A MrPwr controller. Power conversion is handled by a split phase 8KW powerjack inverter. You might get better efficiency with a more expensive inverter, however in our book less than four hundred bucks is hard to beat.

The bottom line is we are just at the tipping point between complete gasoline free boondocking and generator dependant. Since September of last year we put a total of 47 hours on our generator. Our goal is to make that zero.

This year we plan to add 400AH of batteries and 800W solar to meet our goal.

[dzl_]

Echoing what others have already mentioned.
Maximize your solar, you won't regret it.


As to inverter size, a 3000VA/2400W inverter (from a reputable company like Victron) should be able to handle 1 maybe 2 of your large loads at a time, but not 3. Without more detail on the specific loads, its hard to say, but its easy enough for you to determine, by checking the power draw of your devices (and be sure to look at draw, not output--for instance a microwave that is a '1000W microwave' will output that, but will draw more).

[Snaketzu]

Quick note as to my expertise: I have 25yrs experience as a professional electrician, with the past 10 years spent mostly in controls and system design, and the past 5 with a side business consulting, designing, and installing off grid systems for cabins and RVs.


Every time I sit down to design one of these systems, I deal with the same issues with the client. They want to treat a solar system with generator backup as a plug and play replacement for their normal grid tie life. This can be done, but at considerable expense and additional complexity. Neither of these is very desirable, especially in the RV environment.

My first advice is to figure out how to make do with less whenever possible. Try to avoid ANYTHING from a systems perspective that makes heat with electricity. It's just too inefficient. I'm not talking about hair dryers and curlers here. While these are certainly loads that should be taken into consideration, they are very short duration and very intermittent. More importantly, they can all be run off of a single 20A 120V circuit. This is a very important point that I will get to again later.

The next step in this process is to try to avoid inefficiencies, and try to keep the number of components to a minimum. I group these together because they are often the same thing. Keeping the system simple helps it to be more efficient and robust. This has the added benefit of reducing costs.

In keeping with the above two points, I want you to consider a pure 12V DC system with 12V appliances, with a 2000W 120V inverter that has remote on/off capability.

12V AC and 12V refrigerators are out there and the prices are getting more reasonable compared to household equivalents all the time. This accomplishes two things: it removes the need for the large inverter that needs to be on all the time, and it starts with more efficient components. When you remove the inverter from the system, you gain 10% more capacity from your solar system right up front. The 12V appliances are also designed and built to run off of limited systems and are more efficient for a solar system. For instance, not only do the refrigerators typically have more and better insulation, but they have a lower power compressor with a brushless DC motor (which by definition has an electronic controller, thus eliminating startup load). This means compared to an AC refrigerator it will spend more time running but at a lower amp draw which means you don't have to upsize your entire battery bank to handle the potential concurrent amp loads. (If you exceed a certain percentage of your battery bank in simultaneous draw, your capacity is sharply decreased.)

Your 120V loads are now intermittent and can be handled with a few 120V receptacles conveniently placed, with small micro switches on the face plate to turn on the 120V inverter as needed, and then turn it off when it's not so you don't unnecessarily drain your battery bank. You can run your hair dryer OR curler OR microwave OR TV etc. etc. as needed BUT not all at the same time. That shouldn't really be a problem.

Cook with propane. Make heat and hot water with diesel or propane or both. A diesel boiler with a radiant floor system and a couple of fan boxes can handle all of your heating needs, and if you pipe in a heat exchanger from the radiator, you can use it for your driving heat system, too.


Consider this AC:
https://www.mabrurv.com/products/mab...rinter-transit
I know, it seems pretty expensive. BUT it fits into a standard 14x14 roof opening, making good use of ceiling space that is typically underutilized in bus builds. It's also self contained, so you don't need to worry about running lines and making space on the inside for the air unit and space on the outside for the condenser. You should also have at least one and preferably two of the ever popular Maxxair fans for when opening windows and circulating outside air is enough. Spaces under 300sq ft with only one person in them, much less 2+, will see high C02 and decreased O2 levels frighteningly fast. You really should consider an Energy Recovery Ventilator, which is a chore because they need to be modified with 12V fan motors, but it can be done. Anyway, ventilation is an often overlooked item that's very important in a small space.

https://furrion.com/products/10-cu-f...n-refrigerator
Just one of several choices, including GE, for a 12V refrigerator, and that price is list and it can be found for considerably less at dealers.

Of course, all of your lighting will be 12V direct LEDs, with literally hundreds to choose from on eBay and similar.

To make all this run, (warning, YMMV based on way too many variables to easily calculate) you need around 600-800Ah of LiFe04 battery storage and roughly double that in watts of solar panels, with an appropriately sized MPPT charger/controller, and the aforementioned 2000W remote on 120V inverter. That's it. All that money you would otherwise invest in high dollar, large inverters and associated gear can instead be put towards more solar and battery capacity and better quality, more efficient appliances.

For backup, consider ditching the generator and adding an additional alternator to your main drive engine, wired to the charge controller. This will allow you to use the AC as the main vehicle AC while driving, and also doubles as your backup generator. If you absolutely insist on having backup genset, then look at making a "putt-putt" charging generator with a 5HP Honda LP converted engine turning an alternator.

You don't wire 12V DC systems the way you would a house, with a central panel containing individual circuit breakers for each circuit. It's better to use a distributed system instead. Wire a 60A or 100A "bus" (no pun intended) from the front to the back of the RV protected by a circuit breaker at the battery bank. Tap off of this bus in as many locations as needed with appropriately sized wire, individually fused. Just make sure the fuses are accessible in case something happens and you need to swap. I prefer full size ATC fuses because holders and replacements are easy to find, and they are much easier to deal with than glass fuses. You can also use the button type circuit breakers.
DC wiring gets a bad rap. The distributed bus design will mean your system has very minimal voltage drop, so that's been countered. The thing you have to watch out for is the connections, as these become very important the lower the voltage is. All connections should be done with quality crimped on ring terminals and stainless hardware bolted together or to a copper bar. KOPR-Shield on all connections (wire to crimp, crimp to hardware to bar) should be considered mandatory. Use a quality crimping tool, not the mash-together type tool found at WalMart and auto parts stores.

Use these suggestions as a springboard to educating yourself about all of these things. For an RV especially you are your own best mechanic, so you should absolutely do it yourself with a professional looking over your shoulder as needed.

[Rucker]

Nice tips all-thanks!

[WayneTSB]

Originally Posted by Snaketzu

Quick note as to my expertise: I have 25yrs experience as a professional electrician, with the past 10 years spent mostly in controls and system design, and the past 5 with a side business consulting, designing, and installing off grid systems for cabins and RVs.


Every time I sit down to design one of these systems, I deal with the same issues with the client. They want to treat a solar system with generator backup as a plug and play replacement for their normal grid tie life. This can be done, but at considerable expense and additional complexity. Neither of these is very desirable, especially in the RV environment.

My first advice is to figure out how to make do with less whenever possible. Try to avoid ANYTHING from a systems perspective that makes heat with electricity. It's just too inefficient. I'm not talking about hair dryers and curlers here. While these are certainly loads that should be taken into consideration, they are very short duration and very intermittent. More importantly, they can all be run off of a single 20A 120V circuit. This is a very important point that I will get to again later.

The next step in this process is to try to avoid inefficiencies, and try to keep the number of components to a minimum. I group these together because they are often the same thing. Keeping the system simple helps it to be more efficient and robust. This has the added benefit of reducing costs.

In keeping with the above two points, I want you to consider a pure 12V DC system with 12V appliances, with a 2000W 120V inverter that has remote on/off capability.

12V AC and 12V refrigerators are out there and the prices are getting more reasonable compared to household equivalents all the time. This accomplishes two things: it removes the need for the large inverter that needs to be on all the time, and it starts with more efficient components. When you remove the inverter from the system, you gain 10% more capacity from your solar system right up front. The 12V appliances are also designed and built to run off of limited systems and are more efficient for a solar system. For instance, not only do the refrigerators typically have more and better insulation, but they have a lower power compressor with a brushless DC motor (which by definition has an electronic controller, thus eliminating startup load). This means compared to an AC refrigerator it will spend more time running but at a lower amp draw which means you don't have to upsize your entire battery bank to handle the potential concurrent amp loads. (If you exceed a certain percentage of your battery bank in simultaneous draw, your capacity is sharply decreased.)

Your 120V loads are now intermittent and can be handled with a few 120V receptacles conveniently placed, with small micro switches on the face plate to turn on the 120V inverter as needed, and then turn it off when it's not so you don't unnecessarily drain your battery bank. You can run your hair dryer OR curler OR microwave OR TV etc. etc. as needed BUT not all at the same time. That shouldn't really be a problem.

Cook with propane. Make heat and hot water with diesel or propane or both. A diesel boiler with a radiant floor system and a couple of fan boxes can handle all of your heating needs, and if you pipe in a heat exchanger from the radiator, you can use it for your driving heat system, too.


Consider this AC:
https://www.mabrurv.com/products/mab...rinter-transit
I know, it seems pretty expensive. BUT it fits into a standard 14x14 roof opening, making good use of ceiling space that is typically underutilized in bus builds. It's also self contained, so you don't need to worry about running lines and making space on the inside for the air unit and space on the outside for the condenser. You should also have at least one and preferably two of the ever popular Maxxair fans for when opening windows and circulating outside air is enough. Spaces under 300sq ft with only one person in them, much less 2+, will see high C02 and decreased O2 levels frighteningly fast. You really should consider an Energy Recovery Ventilator, which is a chore because they need to be modified with 12V fan motors, but it can be done. Anyway, ventilation is an often overlooked item that's very important in a small space.

https://furrion.com/products/10-cu-f...n-refrigerator
Just one of several choices, including GE, for a 12V refrigerator, and that price is list and it can be found for considerably less at dealers.

Of course, all of your lighting will be 12V direct LEDs, with literally hundreds to choose from on eBay and similar.

To make all this run, (warning, YMMV based on way too many variables to easily calculate) you need around 600-800Ah of LiFe04 battery storage and roughly double that in watts of solar panels, with an appropriately sized MPPT charger/controller, and the aforementioned 2000W remote on 120V inverter. That's it. All that money you would otherwise invest in high dollar, large inverters and associated gear can instead be put towards more solar and battery capacity and better quality, more efficient appliances.

For backup, consider ditching the generator and adding an additional alternator to your main drive engine, wired to the charge controller. This will allow you to use the AC as the main vehicle AC while driving, and also doubles as your backup generator. If you absolutely insist on having backup genset, then look at making a "putt-putt" charging generator with a 5HP Honda LP converted engine turning an alternator.

You don't wire 12V DC systems the way you would a house, with a central panel containing individual circuit breakers for each circuit. It's better to use a distributed system instead. Wire a 60A or 100A "bus" (no pun intended) from the front to the back of the RV protected by a circuit breaker at the battery bank. Tap off of this bus in as many locations as needed with appropriately sized wire, individually fused. Just make sure the fuses are accessible in case something happens and you need to swap. I prefer full size ATC fuses because holders and replacements are easy to find, and they are much easier to deal with than glass fuses. You can also use the button type circuit breakers.
DC wiring gets a bad rap. The distributed bus design will mean your system has very minimal voltage drop, so that's been countered. The thing you have to watch out for is the connections, as these become very important the lower the voltage is. All connections should be done with quality crimped on ring terminals and stainless hardware bolted together or to a copper bar. KOPR-Shield on all connections (wire to crimp, crimp to hardware to bar) should be considered mandatory. Use a quality crimping tool, not the mash-together type tool found at WalMart and auto parts stores.

Use these suggestions as a springboard to educating yourself about all of these things. For an RV especially you are your own best mechanic, so you should absolutely do it yourself with a professional looking over your shoulder as needed.

Fantastic Write Up!

I have a very minimal draw as ours is only for weekend warrioring, but I went with almost everything you talked about in here! 12v EVERYTHING with an on/off switch inverter hooked to a double 110/120v receptacle.

12v is also just so easy to wire!