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Old 10-24-2020, 11:21 AM   #1
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Exclamation Looking for a parts list for solar

Hey everyone, I'm new here and getting ready to build a solar system for my first bus.

I've been researching like crazy, as I'm sure all of you have done before as well, but I can't figure out exactly what I'll need in a cut and dry list of parts.

I'll start by stating what I'm trying to get done, and hopefully, some advice can be given. I've tried the search feature in the forums, so if there was a thread I could have posted this to, I apologize; I'm relatively inexperienced in posting in forums.

I'm hoping to set up full solar for a 40ft bus. I have a family of 4 and a dog, and I'd like to have a system that can handle running a mini-split daily, at least during the peak hours of the day.

After that, I want to have enough power for lighting, charging devices, running a computer, and a full-sized fridge. Along with all the other little things that may be running like fans and water pumps etc

Looking at my electric usage at my current 2300sqft home, we use an estimated 30kwh a day, and while I know I won't need that much power on the bus, I'd like to get as close as I can to that amount of power.

I'm planning on building a li-ion bank with cells as it seems to be the cheapest way to go, but as mentioned in the beginning, the wormhole of trying to find the correct parts is beyond intimidating.

I want to get this done at the very best price possible, as I know what I'm looking to do is bound to be expensive.

I guess the big part for me is getting lost in my attempts to do the math, understand the watts volts amps, etc. and then find the corresponding pieces. The math jumbles my head into a bowl of mush every time i try to get a solid understanding of it.

So, If I could get a fridge and mini-split/ heating AC device recommendations, battery bank size recommendations, and then the number of panels needed to adequately charge the system throughout the day, and additional hardware controller inverter, fuses, cell maintenance devices, etc.

It's a long list of stuff, and if I can get a plain cut and dry answer, that would be awesome.

If I am coming off like a typical crazy newbie with unrealistic expectations, I apologize and hope that others with serious powerhouse set-ups can lend advice and a list of components that they would recommend.

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Old 10-24-2020, 01:29 PM   #2
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To even approach that number you're going to have to go commercial grade panels, most likely 48volt. You could start looking here:
I plan on using these guys but only for a 2kW system
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Old 10-24-2020, 01:37 PM   #3
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Hey Rwnielsen,

Thanks for the reply!

Yeah, I'm unsure of how realistic or necessary it really is to get as much as I'm thinking I want in my head.

I was looking a bit into a 48-volt system but still get lost when trying to piece everything together, I guess I'm really hoping a few guys with massive systems see this post and can give me a rundown of what their system powers, and what they are using to help shape the direction I go.

The way I see it is if I have a full list of parts used, and what they are producing, or more importantly what appliances they are powering daily with their system, I can research the exact components they have in their rig, and try and put together my system by researching what they are using and finding similar components that at the very least meet or exceed the voltage/amp/watts that the recommended components have.
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Old 10-24-2020, 07:00 PM   #4
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This stuff requires actually understanding, hard numbers, not just parts lists.

Aircon off solar is very impractical.

Figure out a genset powered system, both aircon and high-amp charging of a very large battery bank.

That will help reduce genset runtime, to maybe 60-70% of the aircon runtime.

Then add a few thousand watts of solar panels, and that will reduce your genset runtime by a bit more

depending on insolation conditions of course.

Parking in full hot sunshine where shade is available is usually a net negative.

All this is **very** expensive.

A better strategy is to just follow the 60's, relocate to higher altitudes.

Tight and high R insulation helps a lot.
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Old 10-24-2020, 07:41 PM   #5
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A general piece of advice -- Take it piece by piece. Its very overwhelming when you try to design/imagine the whole system from the get got. Take it in baby steps, try to wrap your head around just one piece of the system at a time (beginning with just learning about the basics of electricity). Don't even be thinking about a parts list at the this point in the process you will just be overwhelmed. Focus on conceptual first, then take specifics piece by piece.

Another general piece of advice -- you are starting off on the wrong foot if you set out to emulate your household consumption patterns. This is not what you should be designing for, unless you plan to use a generator or shorepower most of the time. If you try to design for a grid tied lifestyle in an off grid (and space limited) scenario, the costs can be immense (if it is even possible). The main constraint with a bus is you are limited in your array size. I think it pays to shift your mindset, commit to prioritizing efficiency and conservation in your design and in your habits, you can still have as many creature comforts as you can afford (in dollars and watts), But always think through the lens of 'how can I do or design this efficiently'

My knowledge is partial and limited, but I have spent a good bit of time trying to wrap my head around the math, the numbers, and the concepts so I am happy to help with any specific questions you have (and am more likely to do so if they are asked one or two at a time, a wall of questions can be overwhelming).

Something I overlooked when I first started learning was the basic units and terms. When I finally grasped them, it was very helpful, and made a lot of things sorta 'click'


A Volt: is a unit of "electrical pressure." Its the "pushing force" that makes electricity flow in a circuit. It is a measurement between two points, nothing intrinsically 'has' voltage, volts measure the difference between two points.

An Ampere (amp): is a unit of 'electrical current'. In other words a 'flow rate' in an electrical circuit.

A Watt: is a unit of power, volts x amps = watts

An Amp-hour: In the context we use it, it is a unit of energy or capacity (most often battery capacity). An amp-hour = the amount of energy it takes to supply a current of 1 amp for 1 hour.

A Watt-hour: Conceptually the same as an amp-hour, except it is the amount of energy it takes to supply 1 watt of power for 1 hour. To convert amp-hours to watt hours multiply amp hours x voltage. The benefit of watt-hours over amp-hours is unlike amp-hours it allows you to ignore voltage in comparisons.

An Ohm: is a unit of resistance, it is the third component of the fundamental equation in electricity "ohms law" "Voltage = Current x Resistance". You can think of it like electrical friction or resistance, it is the force that opposes voltage (electrical pressure). You won't run into this unit very much but its useful to understand it, and Ohms law on a basic level.

Ohms law:
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Old 10-24-2020, 08:24 PM   #6
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I have 2kW of tiltable PV on my 40-foot bus, divided into two separate systems running in parallel (redundancy is good!), and right now I'm installing a Pioneer 12K minisplit A/C with inverter start and a heat pump. There's no question that my PV won't run it - plenty of others are running 12K minisplits on less PV power and battery capacity than I have, so it will work! Each array of four panels is wired in parallel, each panel is individually fused, then each array's combined 34 amps at 30 volts supplies its own Morningstar TS-MPPT-60 charge controller that in turn charges its own bank of four golfcart batteries connected in series and parallel. Total battery capacity will be about 900aH (half of that practically usable), and that will be plenty for my modest needs. I also have two of the Chinese diesel air heaters for cold days when the sun's not cooperating. The fridge will be a chest freezer with an external thermostat, powered by its own small PSW inverter (maybe a small Exeltech?), then my Magnum inverter will only be turned on when needed. I'm building my bus for extended boondocking - my criteria is that it should comfortably support one person for at least a month off-grid, or two people for at least a fortnight, and that's taking a proper shower every night etc etc (I have 220 gallons of fresh water capacity, and almost that much for waste). I've also got roof space for two tiltable water-heating solar panels that will reduce propane usage year-round, and maybe they'll be enough by themselves in the summer to heat all my water. And if the sun doesn't shine for more than a few days I have a small emergencies-only generator to keep the batteries bulk-charged.

With a 40-foot bus you've got the space to have a lot of everything, so I suggest you simply fit the largest or most of whatever you're having, be it water or waste tanks, PV panels, or anything else. Just fill up all the space, then you won't have any regrets later that you didn't install more or bigger of something! If you carpet your roof with PV panels you should be able to have about 3kW without any problem, and more if you get imaginative. Just bear in mind that the further north you are, the greater the benefits of tilting the panels in the winter to maximize solar harvest when the sun is lowest.

The experts on the Northern Arizona Wind & Sun forum have a lot of good advice on matters renewable, so it's well worth your time to read all you can there. If they say something will or will not work, you'd better believe it!

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Old 10-24-2020, 09:44 PM   #7
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My build uses a mini split / heat pump for heating and cooling, and we run a full size fridge. Your needs sound similar to ours, and we run a 48V bank. Check my build thread out if you have time.

To echo some others here, I think what you need is not a list of parts persay, but a clear understanding of the problem you are trying to solve. These components solve the problem in different ways:
  • Solar panels turn sunlight into energy. In full sunlight a large array can produce several times in excess that which is needed to power all devices in a bus, but during cloud cover, rain, or at night will not produce anything.
  • Batteries store electrical charge for use. The excess from the solar panels can be harnessed here instead of going to waste, this is likely the most expensive portion of any system. They do not generate electricity, almost always have an efficiency trade off, and have limited lifespans. They must also be cared for- over-discharging and overcharging batteries can damage them or cause a fire. Many lithium battery chemistries cannot be charged in freezing temperatures.
  • Solar charge controllers charge your batteries. They take the raw (often high voltage, fluctuating with the availability of sunlight) energy from solar panels and convert it as to be usable by the battery bank.
  • Inverters convert DC (direct current) battery / solar energy to AC (alternating current), mimicking common house power. Inverters have a continuous and surge rating and come most commonly in single phase (110VAC, normal outlets) and split phase (110VAC and 220VAC, dryers, mini splits, air compressors, etc) variants. Additionally, inverter technology is divided into two common groups: HF (High Frequency) which is cheaper, lighter weight (smaller transformers) and generally less capable; as well as LF (Low Frequency) which is more expensive, higher weight with large transformers, and capable of running appliances with high surge loads.
  • Safety equipment such as fuses, breakers, GFI and arc-fault protect against common failure conditions in your system and are used on both the AC and DC side of any system. There's nobody on this site who hasn't blown a fuse or two or have never tripped a breaker- safety equipment is not optional!
There are additional components, particularly things like BMS (Battery Management Systems). There is no one-post all-encompassing reply that can convey what is needed to understand, let alone build and operate, a functioning solar system of the scale you are asking for.

Let us know if you have any specific questions.
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Old 10-24-2020, 10:44 PM   #8
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Yes, it is "possible" to run aircon off "solar alone" for Xmin per day, in ideal sunny conditions

but doing so for hours and hours is not **practical**.

Originally Posted by dzl_ View Post
you are starting off on the wrong foot if you set out to emulate your household consumption patterns. This is not what you should be designing for, unless you plan to use a generator or shorepower most of the time
Critical piece there!

Every dollar spent on reducing electrical consumption will pay off in spades if spending lots of time off grid.

Genset hourly runtime costs are huge! not just fuel but wear & tear, and IMO having it chugging away in the background, most annoying. Especially if others are in hearing range.

So, figure out how to minimize that runtime.

Then put in as much solar as will fit on your roof, with a goal of reducing it further.

But out of all these money-pits, the highest ROI will come from, putting a small fraction of your overall investment in off-grid aircon, into reducing the need to use aircon in the first place!
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Old 10-30-2020, 08:25 AM   #9
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Thank you for all the great responses!

I do understand that I should scale down my usage, I was really posting to see what others have done that really have a massive power solution.

I don't really plan to use as much energy as in my house, but my logic is, if I can get close to that I can hopefully have power for more than a day or 2 if there is no sun, and then never have to fire up the generator if I'm lucky.

I guess the thing for me is finding out how much power can I pull in from having the maximum amount of panels on the roof, and what size battery bank is fair for that.

I've been looking into alternative battery bank sources, such as finding a used electric car battery bank (li-ion and huge storage capacity)

I will look further into the information you all could offer and appreciate any help I can get along the way!

Right now I found some fair prices on 300w solar panels, and what I guess I need to figure out is how to run the system as the whole 48v / 24 volt system still kind of confuses me a bit.

But I'm thinking I can get 2400w on the roof and a massive battery bank underneath, then I guess it's just learning the math and ratios to pick out the proper fuses, charge controller, and inverter?
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Old 10-30-2020, 02:05 PM   #10
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In your current state of knowledge, stick to 12V

yes focus on maxing out your solar production, but for storage, start with 2 or four pair of cheap deep-cycling ordinary flooded lead GCs

in the U.S. maybe $1 per Ah at 12V

Try to keep consumption low enough that say 400Ah is sufficient, fed by your solar plus alternator when driving, shore power when available, maybe an inverter genset.

If not, then Stage 2.

If using lithium, I advise using brand new LFP chemistry cells for safety.

The higher-voltage chemistries as used in EVs are susceptible to thermal runaway (boom bad).

You will then be spending many thousands of dollars on your LFP storage + more infrastructure, and using the genset for at least a few hours a day when off grid.
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Old 10-30-2020, 04:42 PM   #11
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I agree with much of the advice given already by John and Kazetsukai. And I would suggest you look at Kazetsukai's build thread, I think his build is somewhat in the ballpark of what you are imagining (large system, no shortage of creature comforts, A/C heatpump) but is also focused on efficiency and cost conscious. There are some design decisions I would've made differently but that is the nature of a bus, you get to make your own decisions and do as you see fit. Overall its definitely a build I admire, that I suspect you could learn from.

On to some specifics,

I agree with John and everyone else who has said, you definitely want to max out solar to the extent you can.

I feel differently than John does about the voltage. I get his point (12v is simpler and marginally safer in a 12v vehicle), but with an array 2400W, that is almost 200A at 12v it will be quite expensive to buy a 200A or 2 x 100A charge controllers. Moving to 24v cuts the current in half, moving to 48v (not my first choice for a vehicle) cuts current in half again.

This goes back to one of the simple equations I posted above: P = I x V
Double voltage and you half current, power (watts remains unchanged).

I agree with John re: lithium batteries. LFP (LiFePO4) is the safest and most suitable option for mobile energy storage appplications. Particularly considering your current level of electrical knowledge. The stakes are much higher with non-LFP lithium and the learning curve is somewhat steeper (than the already steep learning curve of DIY LFP). Also the cost advantage of used EV cells relative to LFP cells has shrunk considerably in recent years.

Regarding your questions about how much power you might pull in from your PV array, there are many websites and resources that help you estimate this, for your region, There is also a rating on many panels called "NOCT" or "PTC" which is a more accurate rating for real world conditions than the nameplate power rating which is based on 'standard test conditions (STC)' which are roughly a best case scenario.

There are calculators that help you calculate this for your region and conditions, here is one.They can help you estimate how much energy per day you can expect to harvest, by month. The productiveness of your PV array in winter months will be substantially lower than in summer months, so for a fully or mostly off-grid (solar dependent) setup, it makes sense to base your calculations on winter months. Bear in mind these calculators are based on conditions for residential or commercial arrays, conditions of vehicle based arrays may not achieve the same results (panel orientation, panel temperature, and airflow underneath the panels are 3 variables that may reduce the output of vehicle based arrays).

Duckduckgo (or google): Solar insolation + NREL for more info on how to estimate PV production.

The figure you want to determine is Watt-Hours (Wh) or Kilowatt-Hours (kWh) per day. This will give you a ballpark of how much energy you can generate and how large a battery bank you would need.
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Old 10-30-2020, 04:58 PM   #12
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Sure 24V bank would be fine

but starting off at 12V is easier for a beginner

you'll need 12V circuits anyway

The required DC-DC converters are a complication best left to Stage 2 (if) when the bigger (maybe) LFP bank proves necessary.

Nothing will get wasted going from 12 to 24V later.

Personally I avoid inverters as much as possible stick to DC native load devices

stuff designed for mains AC tends to be very inefficient, especially in poorly regulated Amerika
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Old 10-30-2020, 09:38 PM   #13
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Originally Posted by john61ct View Post

Critical piece there!

Every dollar spent on reducing electrical consumption will pay off in spades if spending lots of time off grid.

Figure out your power budget then look for ways to trim it. Then start designing a solar system to support it.
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