Let me know if I have this right?

porkchopexpress

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Configuring a system "on paper" and just want to make sure I'm correctly understanding how all the components and numbers work together.

(2) 12V/200aH LiFePO4 batteries in series for a 24V/200aH system, handles 4800 watt hours?
(6) 320W/24V solar panels. Wired in parallel because they're already at 24V
EPEVER 80A MPPT Solar Charge Controller 12V/24V/36V/48V DC. The 1920W from the panels divided by 24V system tells me 80A is the proper rating?
Power Bright ML2300-24 2300 Watt 24 Volt DC To 110 Volt AC Power Inverter

As mentioned before I had looked at the LV2424 all-in-one, but wanted to look at this from a standpoint of individual components, as this would give me a better understanding of how and why everything in the solar system works the way it does...
 

rmaddy

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24V (really 25.6V) at 200Ah is 5120Wh. So basically correct.

Your 320W panels are not 24V. Look at the Vmpp and Voc values. Well over 24V. There is benefit to putting some in series. 2S3P or 3S2P would be better than 6P. You’ll get better low light performance.

You are correct on the 80A charge current for the SCC. You do need to make sure the max PV input voltage can handle the total Voc of your panel arrangement, adjusted for the coldest temperature you will encounter.
 

porkchopexpress

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Your 320W panels are not 24V. Look at the Vmpp and Voc values. Well over 24V. There is benefit to putting some in series. 2S3P or 3S2P would be better than 6P. You’ll get better low light performance.

Yeah this is the part I need to gain more understanding about! Initially I was thinking 24V battery meant 24V panels were necessary.

So it looks like the all-in-one kit is more simplistic and "idiot-proof" in terms of being able to screw it up, but more expensive than shopping around for the individual components that do the same thing, then mounting them on a board.
 

porkchopexpress

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So, if I choose 12V panels vs. 24V, this means that I would (roughly) need to have twice as many panels to accomplish the same amount/rate of charging, right?
 

robby

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So, if I choose 12V panels vs. 24V, this means that I would (roughly) need to have twice as many panels to accomplish the same amount/rate of charging, right?
Your panel voltage will not be 24V it will be higher. As stated before look at the Vmpp and Voc values on the specification sheet or post the make and model of the panels. The next person to come along can then help you figure out the right arrangement.

Just so you understand, the panels may be wired up to obtain a certain voltage for example 150V and that is fed into your charge controller which will lower it down to the voltage needed to charge your batteries and run the Inverter.


I
 

sunshine_eggo

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Due to the evolution of the industry prior to MPPT, there are such things as 12V and 24V panels, though their relevance as such are less important in these days of MPPT. They are 36 cell and 72 cell panels, respectively. They have a Vmp of about 18 and about 36V, respectively. It is common to find those advertised/documented as 12V or 24V NOMINAL. They are the panels you would need to use on a 12V or 24V PWM controller, respectively.
 

Rednecktek

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Translation: "This panel can charge a 12v battery, but not a 24v" = 12v panel. "This panel could charge a 24v battery but doesn't make enough to charge a 48v" = 24v panel. It's all marketing speak to tell you what your nominal voltage should be when using the panel they're selling you.
 

Steve_S

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Configuring a system "on paper" and just want to make sure I'm correctly understanding how all the components and numbers work together.

(2) 12V/200aH LiFePO4 batteries in series for a 24V/200aH system, handles 4800 watt hours?
(6) 320W/24V solar panels. Wired in parallel because they're already at 24V
EPEVER 80A MPPT Solar Charge Controller 12V/24V/36V/48V DC. The 1920W from the panels divided by 24V system tells me 80A is the proper rating?
Power Bright ML2300-24 2300 Watt 24 Volt DC To 110 Volt AC Power Inverter

As mentioned before I had looked at the LV2424 all-in-one, but wanted to look at this from a standpoint of individual components, as this would give me a better understanding of how and why everything in the solar system works the way it does...
Your off to a fair start but lets do this a tad differently to save you hassle & cash. Most folks like that.
1) Build a single 24V/8S 200AH / 5120Wh or 5.12kWh pack. This requires only One 8S BMS, and One Fuse (200A). If you are setting up a 24V based system then Build a 24V Battery, don't put two 12V in series unless you have no choice (like buying rebuilt dropins)

2) The EPEver is a Good Quality Value brand and pretty flexible, there are several models, It may be more prudent to go with the 100A Model because a 200AH Battery can take 100A Charge and if you add another in Parallel for more Amp Hours the two battery packs will divide the charge and virtually everyone grows their system at least Once but usually more... Happens ALL the time, so this is a bit of future-proofing.

3) SOLAR PANELS. Forget 12V panels they are 3x more expensive because they are NICHE. the "24V" Panels are always higher voltage and best bang per buck. See the Three Examples below. Panels placed in Series increase Voltage while panels in Parallel increase Wattage, so string configuration is essential to get the most out of the panels.

4) Powerbright Inverter, this is a mid-low quality "Value" product. Coin Toss, efficiency, longevity and other things to consider. Are you going to "depend" on this system or is it something that's just a hobby ? Depends on use and how necessary (dependable) you need. AIO's do make it a LOT simpler and saves on many ancillary bits like breakers, fuses, wiring etc... BUT there are drawbacks, like higher standby power consumption and such. Also whether or not you want a High Frequency MOSFET Based Inverter/Charger or a Low Frequency Transformer base.

Solar Input -> SCC -> Batt.
I run 24V, my solar input can be 200VDC and 2100W on a sunny day and the SCC turns that into 80A @ 27.5V (bulk charge rate). If I wanted to do that with 12V/200W panels it would take a lot more panels at a much higher cost and less efficient. A GOTCHA ! Shading can really mess stuff up ! If you have 4 panels in a string series and one panel gets shaded that entire string takes a hit ! So the layout and setup is really important to prevent reduce that.

Hope it helps, Good Luck.


Canadian Solar 335W mono Solar Panel​

Watts (STC)335 W
Max Power Voltage (VMPP)37.8 V
Max Power Current (IMPP)9.0 A
Open Circuit Voltage (VOC)44.5 V
Short Circuit Current (ISC)9.57 A
Max System VoltageDC 1000 V

LG NeON 2 340W mono Solar Panel​

Watts (STC)340 W
Max Power Voltage (VMPP)34.5 V
Max Power Current (IMPP)9.86 A
Open Circuit Voltage (VOC)41.1 V
Short Circuit Current (ISC)10.53 A
Max System VoltageDC 1000 V

Longi 355W mono Solar Panel​

Watts (STC)355 W
Max Power Voltage (VMPP)33.5 V
Max Power Current (IMPP)10.6 A
Open Circuit Voltage (VOC)40.7 V
Short Circuit Current (ISC)11.1 A
Max System VoltageDC 1000 V
 

Rednecktek

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For my understanding, does this mean "will not charge 24v battery" or "will charge, but will do so very slowly and inefficiently"?
It won't reach enough voltage to feed a 24v, but it will feed a 12v. Most of the 100w "12v panels" generate about 18-20v, so it'll charge a 12v, but doesn't generate enough to feed a 24v. Even many "24v panels" are actually trying to produce 30-40v, so enough to charge a 24v, but not enough for a 48v.

The VoC listing on the panel specs will be the maximum theoretical voltage the panel can produce. When you're charging a system you need MORE voltage to charge than the battery actually holds to get electrons to flow into the battery.

When you see "12v", "24v", "48v" on systems and batteries and the like, that's the "nominal voltage" of the system. When you throw a meter on a 12v battery, it should easily read 12.5-13.5v depending on the charge and type, but we still call it "12v" because of old timey specs back when these things were being invented. Even modern LiFe batteries will show an easy 14v on a meter, but we still call it a "12v nominal" system. Old nomenclature holds on forever! :)
 

porkchopexpress

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When you see "12v", "24v", "48v" on systems and batteries and the like, that's the "nominal voltage" of the system. When you throw a meter on a 12v battery, it should easily read 12.5-13.5v depending on the charge and type, but we still call it "12v" because of old timey specs back when these things were being invented.
Ah... right, like the inverter in my work van... the digital display shows like 12.8, and more while the vehicle is actually running and charging the battery. Starting to grasp these concepts!
 

porkchopexpress

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Your off to a fair start but lets do this a tad differently to save you hassle & cash. Most folks like that.
1) Build a single 24V/8S 200AH / 5120Wh or 5.12kWh pack. This requires only One 8S BMS, and One Fuse (200A). If you are setting up a 24V based system then Build a 24V Battery, don't put two 12V in series unless you have no choice (like buying rebuilt dropins)

Sorry, what's the 8S BMS? I've been reading up and checking out various Youtube tutorials, but didn't see that component in the mix?

4) Powerbright Inverter, this is a mid-low quality "Value" product. Coin Toss, efficiency, longevity and other things to consider. Are you going to "depend" on this system or is it something that's just a hobby ? Depends on use and how necessary (dependable) you need. AIO's do make it a LOT simpler and saves on many ancillary bits like breakers, fuses, wiring etc... BUT there are drawbacks, like higher standby power consumption and such. Also whether or not you want a High Frequency MOSFET Based Inverter/Charger or a Low Frequency Transformer base.

Yeah, I was more or less searching Amazon for an inverter with a certain set of specs... not for the purpose of buying that particular one, but making sure I have the understanding of how the numbers fit together.

I have a vacation lake house and want to build a small cabin on the property... a rustic bunkhouse that sleeps three more people. The main house has regular power, but I thought it would be cool to have this extra unit on solar. So it's not going to be critical for survival or anything like that.
 

Rednecktek

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Yup. You ever seen pictures or videos of people building their own LiFe batteries? You see how they stack the blue boxes together and connect them up in series? Well, if you look at a car battery, you'll see 6 plugs or holes in the top. Lead acid batteries are essentially doing the same thing with ~2v cells strapped together to make a final voltage of about 12v. If you were to cut one open (please don't without the proper safety equipment!) you'd see 6 plastic boxes full of plates and acid all connected together along the top. Same concept, older technology.

I'm sure at some point back in the day there was a conversation that went something like this:

(Insert Sepia Tone Filter Here)

Engineer: Hey boss, I found a way to strap all these lead acid cells together to make a workable battery!
Marketing: Really? That's great! Tell me about it.
Engineer: Well, I found that if I connect up all these 2.2132 volt cells together we get 13.2792 volts which is enough to make the car work.
Marketing: So 6 of the 2 volt cells strapped together?
Engineer: 2.2132 volt, not 2 volt.
Marketing: That's what I said, 2 volt. That 12 volt setup should work nicely.
Engineer: It's actually 13.2792 volts, not 12 volts.
Marketing: But 13 point whatever volts sounds stupid. We'll go with 12 volts.
Engineer: (sigh) OK, sure, whatever.

:LOL:
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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A BMS (battery Management System) has sense leads for each cell.
12V Battery uses 4 cells, 24V requires 8 Cells and 48V requires 16 cells. So for a 24V System you need an 8S BMS.
See this resource I wrote a while back, it will tell you how to build/assemble an LFP Pack and other important tidbits.
Luyuan Tech Basic Lifepo4 Assembly Guide

One rule which REALLY Applies to Solar Systems is KISS ! Keep It Sweet & Simple.
This is the real beauty of All-In-One systems and they also save you a boat load of cash on "Balance of System" components like breakers, wiring, shunts, fuses and more. AIO's are internally "modular" so they are serviceable, they incorporate the Solar Charge Controller (SCC), the Inverter & the Charger all into one tidy box.

Please check this out and it will answer many other questions: Will also has several vids with these.

Word of advice... NEVER USE A FREAKING EXTENSION CORD ! to or from any solar system unless its a "car inverter" with plugs for an extension cord. Do wire to a small SUB-PANEL like a Square-D Q04L100s which can take 4 std breakers or 8 1/2 sized AC Breakers for your output wiring,

REF: https://www.se.com/us/en/product/QO...onvertible-main-lugs-nema1-surface-cover-csa/

See the logical wiring diagram for my systems here:
 

porkchopexpress

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One part I didn't list above would be the wiring after the AC comes out of the inverter (or the all-in-one). I was thinking a breaker box with circuits to a few wall outlets, ceiling fan, LED lighting.

Would this be more or less how to wire it? With the exception that I'm not doing anything with 240V, and the two "hot" connections would both come from the same output on the inverter? And, how will I know how many amps the main breaker switch will be?


Inside-Main-Breaker-Box-Panel-120V-240V-NEC.png
 

Steve_S

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I am 120V Only, this is why I showed you my setup without a 240V Main Breaker. The 4-Slot model is identical to the 8/16 Breaker model here which is in my cabin and shows the Bridge Wire (8 AWG) to connect both sides, this runs all the breaker slots. Also the 240 Breaker will be a problem. If you look at Page-1 of My System Page you will see that the AC runs from Inverter(4000W LF) to Q045 45A Breaker then to the smaller sub-panel where I run the Cabin circuit (30A Breaker) from and power the Pumphouse (well pump & light) with a 15A Breaker.
My Samlex Inverter outputs 4000W@120V=33.3A with surge potential up to 12,000W/100A.

- A Point: Everyone thinks of the big numbers but we must remember that it is cumulative loads running that we have to think on. I have no yet managed to hit an Overload State ! That includes running my 3HP Compressor (it IS mean ! wanna see surges ?) and even Worse the MIG Welder which hits Surge every trigger pull ! Now I do NOT use those off the Solar, I have a Big Genny for that "Nasty & Rude stuff" but I have tested it and it does take it quite well. NOTE: I would Never Ever do that with anything less than a Tier-1 Grade Inverter. I have a "Value Tier-3" Yiyen APC-3000W/9000W Low Frequency Inverter which I started with, it could handle the Compressor but NOT the Mig but "boy that pushed it!" poor thing got Really Really warm in no time. I did trips its internal "push button" breakers.


1608234476503-png.30542
 

porkchopexpress

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Thanks for all the replies. This thread has been very educational and has increased my grasp of some of the basic concepts of a solar plan.

Another thing I scoped out today was heating/cooling my planned mini-cabin. I researched "mini split" units, but according to what I'm seeing, they use 600 watts at a minimum. According to calculations, to accommodate something like that I'd need to go to about 18 solar panels instead of 6, 800aH batteries rather than 200, plus much higher rated charge controller and inverter. Unless anyone knows something I don't, it probably wouldn't be feasible and would run the equipment cost much higher than I'd want to pay for a somewhat hobby project.
 

Rednecktek

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Thanks for all the replies. This thread has been very educational and has increased my grasp of some of the basic concepts of a solar plan.

Another thing I scoped out today was heating/cooling my planned mini-cabin. I researched "mini split" units, but according to what I'm seeing, they use 600 watts at a minimum. According to calculations, to accommodate something like that I'd need to go to about 18 solar panels instead of 6, 800aH batteries rather than 200, plus much higher rated charge controller and inverter. Unless anyone knows something I don't, it probably wouldn't be feasible and would run the equipment cost much higher than I'd want to pay for a somewhat hobby project.

Yeah, the general consensus with heating is "Anything But Solar" because it eats battery banks alive! As an example, a bog standard 1500w room heater will drain a 100Ah LiFe battery in less than 45 minutes, or a Lead Acid in 20 minutes. If you want to look at heat options, I'm a big fan of the Chinese diesel heaters and have 2 installed in my cabin. They require having fuel, but at 6 gallons a week to keep the place warm when it's 10F outside, no exhaust fumes in the house, and only needing 12v (or 24v are available) it sips the electrical too.

Cooling, well, that's what fans and swamp coolers are for. :)
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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Gotta chime in on heating.
While I am not a Tiny House on wheels my place is right sized for me & Maggie. I buit my home with a Frost Protected Slab Foundation with Radiant Heating in the concrete slab, it's great to step on a floor at 77F when it is -10F outside, or to crawl into a warm bed at 77F ! In my case the Slab is also the thermal regulator & control so in summer I don't get cooked but that also has a lot to do with the Cool Roof System and Rain Screen siding setup too. 105F outside never gets above 82F inside and no AC or Fans either.

All of this said, it is -30C/-22F outside right now. Heating system runs a total of 4 hours in 24 hour period to maintain 25C/77F, electrically run but LPG fuelled. The Radiant System at first was a daunting notion BUT the answer was AT HAND and a Great Solution too. This company provided me with everything needed even the Takagi on-demand heater (cheaper than many places at that) and it is all Top Quality High end products too. Check out the company, they are in Vermont and ship quickly. http://www.radiantcompany.com/ Really great folks and extremely helpful with marvelous support. NOTE: I very rarely praise any company but These guys deserve it !

Radiant Heating can be installed in many ways and can also be your hot water source with the correct implementation and that can kill two birds with one stone.

Note on LPG/Propane.
Being Low Pressure Gas, it is quite possible to use BioGas generated from waste. BioGas from waste is used all over the world and even in places like Alaska ! If anyone tells you different, walk on... There are simple kits and complex industrial setups and it is also very easy to DIY your own. There are MANY BioDigester/BioMethane articles, plans & kits available and it does work. Some Examples here: https://www.builditsolar.com/Projects/BioFuel/biofuels.htm#Methane
 
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