what components for my first build for max efficiency

[patriots]

I have 4 LiTime 12v 100ah batteries, 60A controller, 3kW PSW inverter, and several 265w panels.. im a bit confused on the 3k vs 2k inverter options to preserve my batteries and optimize my system. also the mppt controller vs standard. i don't think mine is mppt. I just don't have the knowledge to put this together correctly for best results of all components, or if I even have the correct components to begin with. This will be for a small back up home system.

any advise is welcomed.

TIA

chris

 

[MichaelK]

If you don't even know what you have, why don't you take pictures of every single component and post them here, so we can figure out how to put it together. Be sure to get pics of the back of your panels, of the specifications sticker.

 

[patriots]

https://a.co/d/aXjHdqq controller
https://a.co/d/hGFjs1r inverter
panel
and as stated above 4= 12v 100ah lifepo4 batteries

 

[MichaelK]

Your controller is PWM, which means it just acts as on on/off switch to prevent over-charging. It does NOT transform the incoming solar voltage down to battery charging voltage like a MPPT controller will. With a Vmp of 31.4V, these panels are totally unsuitable for a 12V battery system. Voltage that high could potentially damage your batteries, but more likely, the resistance of the batteries will drag the operating voltage of the panels down to ~15V? That means your 265W panel becomes a 105W panel.

It would work reasonable well for charging a 24V battery bank, but each panel would need to be wired in parallel, not series, so you'll need copper wire thick enough to carry the relatively high current from the array to the controller. Assuming you might see as much as 32A potentially coming from the panels, you'll need at least 8 gauge wire to carry the load. 10 gauge is rated for 30A, and might be marginally acceptable, but you're pushing that wire close to or past it's limit.

Since you have a 12V inverter, you are making some poor choices here. 3000W is really above what is practical for 12V. Any chance you can sell it and purchase a 24V inverter instead? Sticking with 12V with what you've already bought is mostly a mistake.

First, four 12V batteries in parallel will be very hard to keep balanced. One battery will be always charged better than the rest, and one will always receive less current than the rest. If the manufacturer rates those batteries as being able to be wired in series, I would go with at least 24V.

If you decide you don't want to give up 12V, then get rid of that PWM controller and replace it with a MPPT controller. How many of those 265W panels do you actually have? If it's an even number, you could wire them in series pairs, for a Vmp of ~63V. A entry-level MPPT controller is Epever's Tracer 4210AN, which can handle two of those panels in series. With four of those panels, you could wire them 2S2P into the controller. That means two parallel strings of two panels in series.

With three panels, it's a bit more difficult. Three in series would give you a Voc of ~116V, so you need a more expensive higher-voltage controller like the Tracer 6415AN or 8415AN. The 60A version is 200$ on Amazon right now.

So, you've got to make some choices now to fix your mistakes. Get rid of your cheap PWM controller and replace it with an MPPT, or replace your 12V inverter and go with a 24V version. The LiTime manufacturer states their battery can be wired in series, up to four, so you have the option of creating either a 24V or 48V system. If it was me, I'd try to get my money back and replace both the controller and the inverter with better choices.

​

 

[MisterSandals]

I just don't have the knowledge to put this together correctly for best results of all components, or if I even have the correct components to begin with.

This is hard to watch. You need to stop buying stuff until you get this worked out.
It sounds like most of all you want t o make your 4x batteries work and thats doable.

Remember, the SCC is the heart and brains of your system and worth investing as much as you can there.

Do you have a budget or level of reliability in mind?

This will be for a small back up home system.

Is this keeping a medical device powered to keep someone alive or (hate to say "just") to power a beer fridge?

 

[patriots]

well guys, that's why im here.. like i mentioned, Im trying my best to put together a system that makes sense, but obviously, im not an expert on this stuff...mistakes will be made. The "make better choices" comment seemed a little funny considering Ive already said I don't have the knowledge to build a system the way you "experts" would.. right? but thanks for the encouraging words.

I picked up 6 of these panels (cheap) long after i had already purchased the inverter, and controller. I can probably return/replace some of these other components to make it work better, but id like to be able to use at least 2/4 of these panels for the system.

probably even return the batteries for 2-24v instead. just needing to know what will make this as simple to use , and efficient as possible?

thanks again

 

[patriots]

This is hard to watch. You need to stop buying stuff until you get this worked out.
It sounds like most of all you want t o make your 4x batteries work and thats doable.

Remember, the SCC is the heart and brains of your system and worth investing as much as you can there.

Do you have a budget or level of reliability in mind?

Is this keeping a medical device powered to keep someone alive or (hate to say "just") to power a beer fridge?

what else is there to buy? besides hardware to build a components board? without the understanding of how it works, these items obviously show the guy like me, just enough to get us to buy it thinking it'll work.. I have a nephew with diabetes and we at minimum want to power a small fridge for his insulin, but a more powerful system would be ideal.

 

[MisterSandals]

I have a nephew with diabetes and we at minimum want to power a small fridge for his insulin, but a more powerful system would be ideal.

You need to figure out how much power you use on a daily basis (watt hours per day) so you can determine how much you expect your system to produce. This is the only way to size a system.

I can probably return/replace some of these other components to make it work better, but id like to be able to use at least 2/4 of these panels for the system.

Depending on your power needs, we can figure out which can be used and which should be replaced if possible and which will not work at all.

The inverter which draws 3000W+ at 12V is completely unusable. If it were 24V or 48V then it would be more likely useable.
3000W / 12V = 250A which is absurd.

The solar panels look like they can easily be put to use.

But the next step is to figure out you power use and expectations for this system.

 

[MichaelK]

what else is there to buy? besides hardware to build a components board? without the understanding of how it works, these items obviously show the guy like me, just enough to get us to buy it thinking it'll work.. I have a nephew with diabetes and we at minimum want to power a small fridge for his insulin, but a more powerful system would be ideal.

OK, here is what you can do to make this a well-functioning system. Wire your 12V batteries 2S2P. That is two parallel strings of two 12V batteries wired in series to make a 24V battery bank. Use a minimum of 4 gauge copper wire between the batteries, and to the inverter. A gauge or two smaller if you can afford it.

Get rid of the PMW controller, and buy a MPPT. This 80A Epever will work for you for 352$ on Ebay. You might get by with a somewhat cheaper 6415, but you won't have any headroom for expansion. If you want to guarranty even more potential for future expansion, select the 8420 or even the 10420.


Get rid of the 12V inverter and replace it with a 24V version. I'd take a look at Samlex. The PST-2000 was my original choice, but it's price has gone up recently, so maybe look at the PST-1500. That will be big enough to run lights, TV, and a refrigerator. You have to choice of either using the NEMA plugs in the front, or hard-wiring the inverter directly into a main electrical panel.


The 8415 charge controller has a 150V limit, so you could wire three of your 265W panels in series for a Vmp of ~94V. The Voc will be 116V, but raise up to 145V at -40 degrees. That should be within the safe limit of that controller. You could wire two parallel strings of your three 265W panels in series to use all six panels. A total of 265W X 6panels = 1590W. Good array size for a 24V system. Even in December, I'd expect that array size to make you at least 4kWh of power on clear, sunny days.

If you want even more potential for future expansion, look at the Tracer 100A 200V controller, at 413$. This would allow you to buy and additional two or three panels to upgrade the array wattage all the way to ~2400W. Wire six panels as 3S2P, eight panels as 4S2P, or nine as 3S3P.





To simplify future expansion, replace array fuses with a combiner box. For three parallel strings of solar, fuses or breakers are manditory. But, even with only two strings, a combiner breaker box simplifies your life. Hunt for deals online. I've gotten a six-bay Midnight combiner for 63$. 12AmpDC breakers would be appropriate for your solar strings. Do NOT try to substitute cheaper AC breakers. They are dangerous for handling DC current.

 

[patriots]

You need to figure out how much power you use on a daily basis (watt hours per day) so you can determine how much you expect your system to produce. This is the only way to size a system.

Depending on your power needs, we can figure out which can be used and which should be replaced if possible and which will not work at all.

The inverter which draws 3000W+ at 12V is completely unusable. If it were 24V or 48V then it would be more likely useable.
3000W / 12V = 250A which is absurd.

The solar panels look like they can easily be put to use.

But the next step is to figure out you power use and expectations for this system.

honestly, a mini fridge and possibly a couple of smaller space heaters and a way to cook meals.. (grid down scenario for very basics) But having more power stored as backup or a rotation option for use is all im looking for. (charging a battery or 2 while using a battery or 2.) If i get the same inverter in a 24v 200w version, and an mppt 30 or 60A controller, would that do well with the panels I have? also, running the batteries in series/parallel or exchanging for 2-24v 100ah batteries.. wouldn't that be simpler? I know I may have to spend more money, but Im not gonna spend hundreds more. upgrade SCC and inverter to work better with 24v batteries

 

[MisterSandals]

honestly, a mini fridge and possibly a couple of smaller space heaters and a way to cook meals..

Do you realize that a small space heater is likely about 1500W? A stove could be even higher.

4x 100Ah x 12.8V = 5120Wh

You would be able to power your mini fridge for a day along with about 3 hours of 1 small space heater.

To recharge from empty this in a typical day, 3.8h of quality solar in january (see attached):

5120Wh / 3.83h = 1337W of solar operating at 100% (perhaps 1800W of panels).

1337W / 28V battery charging = 48A solar charger (very reasonable at 24V battery)

 

[Bluedog225]

Welcome.

You are all over the map. Your latest post dramatically changed your request.

This group can help you learn. As already suggested, start with understanding how many watts you need per day.

You can get there by understanding volts times amps equals watts. volts*amps=watts

With this formula you can look at any of your appliances and determine how many watts you need.

Once you get there, come back and we can help pick some equipment.

 

[patriots]

Welcome.

You are all over the map. Your latest post dramatically changed your request.

This group can help you learn. As already suggested, start with understanding how many watts you need per day.

You can get there by understanding volts times amps equals watts. volts*amps=watts

With this formula you can look at any of your appliances and determine how many watts you need.

Once you get there, come back and we can help pick some equipment.

ok.. forget cooking.. I don't even "need" it for that and forget the heaters too... jeez. Can i just power a basic mini fridge on 2-24v lifep04 batteries with a 24v inverter and an mppt scc? I don't know what you guys know and would like reading responses that don't make me feel so stupid. even though im sure you think I am because im not as savy as you concerning solar yet. I don't have the actual appliance i would be using yet and figured it would be better to have a system that would be MORE than required to power items mentioned above than one that's not.

so, are the following components a good start to store minimal power?

2=265w panels (I have a total of 6 but don't think i would need all of them to power up 2 batteries at a time)
60A MPPT SCC
2000w 24v inverter
2=24v lifep04 Li Time batteries

That's all Im asking for at this point. If you feel its necessary to remind me oh how uneducated I am, you don't need to reply.. Maybe someone who isn't as "smart" might be willing to help a new guy out without the condescending remarks.

Thanks anyway

 

[Bluedog225]

We’ll be happy to help. How many watts do you need?

 

[Bluedog225]

And yes, you can start with what you have and learn by using it. It’s good you have lithium batteries. Lead acid are earlier to kill.

 

[MisterSandals]

Maybe someone who isn't as "smart" might be willing to help a new guy out without the condescending remarks.

I hope you didn't take my comments as condescending, i was trying to be informative and helpful.

2=265w panels (I have a total of 6 but don't think i would need all of them to power up 2 batteries at a time)

I'd plan on using at least 4 to start with since 2S2P is easy and only requires 1 pair of Y connectors:

https://www.amazon.com/BougeRV-Connectors-Branch-Parallel-Adapter/dp/B0753X68PS/

Down the road, you will want to use all your panels. There's <almost> never too much. And depending on the max input voltage of the SCC you choose, you can put either 2 or 3 panels in series, twice for 2S3P or 3S2P. 2S3P will work with a 100V max SCC and a 3S2P will require at least 140V max input voltage.

For an SCC, if you are in this for the long haul and are depending on a high level of reliability, this is where to invest in a little better equipment. If you have a budget in mind or a reliability/longevity target, you can get a number of recommended SCCs.

60A MPPT SCC

Are you looking at the EPever recommended in post #9 by MichaelK?
This is a good choice for middle of the road price/quality/reliability from what i have seen/read.

For an inverter, i don't have a feel for what to recommend since you mentioned a few big watt items (over 1500W). Now is probably the best time to get the inverter you can grow into. They're not cheap.
The 2000W Samlex you list is a good, better than average choice. You may get by running a fridge and small heater concurrently but it'd pushing it.
If it wasn't clear, with a 24V battery (your 4 as 2S2P, or a different 24V 2x in parallel) will handle up to about 2000W well:
2000W / 20V cutoff / .85 = 118A (very reasonable fusing and wiring rated for 150A)
3000W / 10V cutoff / .85 efficiency = 177AA (wiring and fusing which is manageable but sized over 200A)

Hopefully this is helpful. I think you're on the right track.

 

[Dagoth Ur Does Solar]

ok.. forget cooking.. I don't even "need" it for that and forget the heaters too... jeez. Can i just power a basic mini fridge on 2-24v lifep04 batteries with a 24v inverter and an mppt scc?

It's mostly that one of the very early steps in the planning phase for your system should be "what do I need it to do?" - and if the answer is "run a mini fridge or a chest freezer overnight" that would be a hugely different equation than "I need to run space heaters overnight".

To give you a real world example, my chest freezer uses something like 1 kilowatt hour in a 24 hour period. If you had a 1500W space heater that only ran for about 10 minutes every hour to heat a room, that would be over 6 kilowatt hours- easily much more if it needs to run for longer.

A system to run a space heater for a reasonable period of time can require a far larger battery bank than to run a chest freezer.

Basically, I think we all would encourage you to have a good idea of what you need your system to do and let the good folks here help make recommendations on what to purchase rather than just buying stuff and trying to throw it together.

 

[Rocketman]

One other item I consider essential is a shunt based battery monitor - like. Victron Smartshunt or Victron BMV712 (there are other ones too). The reason I consider it essential is at a glance you will know if your batteries are full or empty- Lithium batteries have such a flat voltage curve - it is impossible to tell by voltage alone.

Also, I agree with getting the mppt solar charge controller.

24v will be better than 12v - one other thing the 12v batteries in series will get out of balance over time. Thus I would use the Victron shunt and hook up the mid-battery monitoring. That way you know when you need to manually recharge them at 12v.

The reason people here keep saying you are “doing it wrong” is because you are buying stuff before you plan your system.

I would recommend:
1. Start by figuring out in watts what you must power in a day. If all you must have is the fridge, then that’s not much, but you also mentioned cooking, heating, etc. The high watt items quickly ramp up the system from a smaller to big very quickly(and ramp up costs too). The inverter purchase is the biggest one and you need to get it right. Too small or wrong voltage and you are rebuying it.

2. Draw up a diagram showing each item with the wires (and wire sizes) fuses, etc. we are very good at spotting errors that way - it is much harder in a written paragraph.

3. Then start buying stuff once YOU know and understand each item. Remember you are the system engineer- it is your job to make sure it all works together as it should.

Along the way you will discover several different price ranges and quality levels (usually called tiers). I like Victron stuff (for lots of reasons) but it is more expensive. Sometimes it’s worth it - sometimes not.

Good Luck!

 

[xjaw4]

The reality of the situation is that even folks with a much larger setup than you are planning may not generate enough power every day to run a fridge in the winter. It is valuable to have more than on way of doing things. Right now tractor supply has an 800w inverter generator on clearance for $169. A propane butane camp stove can be purchased from Walmart for $15. There is a lot that can be done on a small budget. Getting the used solar panels was good, as others have said a mppt charge controller will help make the most of them. A table top ice maker and an insulated cooler could help keep insulin fresh without continuous power.

 

[patriots]

I appreciate the advise. Honestly, I can’t say I have “plans” for what it will be used for. Just a decent backup system to help if we have a grid down scenario. I can improvise if I don’t have a solar system at all. I know there are other ways to survive without electricity, however, needing a degree in electrical engineering to build a good system isn’t what I was dealt. A good system that I can use to assist in normalizing life a little in the event of an extended power outage is all I’m looking for. The balancing act of components is way past my pay grade. I wish I understood it better, but it is what it is. I already have a smaller system in the EcoFlow delta 2 with a folding 160w EF panel, and an extra EcoFlow battery for a more mobil option but was just wanting to set up a more powerful system for emergency use if needed. My head hurts from all the watts, volts and amps talk.. lol. Thanks for the help

 

[Reed Cole]

I appreciate the advise. Honestly, I can’t say I have “plans” for what it will be used for. Just a decent backup system to help if we have a grid down scenario.

That's a valid approach. At a certain point when you're off grid you just have to make it work anyways.

 

[Dagoth Ur Does Solar]

needing a degree in electrical engineering to build a good system isn’t what I was dealt. [...] The balancing act of components is way past my pay grade.

Honestly, if you REALLY have no interest or capability to learn this stuff over time, you really can just buy something like one of the nicer EcoFlow units and their solar panels, and you instantly have a battery backup and solar system that requires no real assembly or knowledge on how to use.

Plug it into a wall outlet, plug in the solar panels, and plug in whatever the hell it is you want to run.

Just to clarify, I'm not trying to sound demeaning- there's absolutely nothing wrong with buying one of those consumer style units- it sounds like you're in the target market for that. They do what most people need during a power outage in a clean package.

 

[Bluedog225]

It will be a lot less expensive if you learn some basic stuff.

 

[krby]

I appreciate the advise. Honestly, I can’t say I have “plans” for what it will be used for. Just a decent backup system to help if we have a grid down scenario. I can improvise if I don’t have a solar system at all. I know there are other ways to survive without electricity, however, needing a degree in electrical engineering to build a good system isn’t what I was dealt. A good system that I can use to assist in normalizing life a little in the event of an extended power outage is all I’m looking for. The balancing act of components is way past my pay grade. I wish I understood it better, but it is what it is. I already have a smaller system in the EcoFlow delta 2 with a folding 160w EF panel, and an extra EcoFlow battery for a more mobil option but was just wanting to set up a more powerful system for emergency use if needed. My head hurts from all the watts, volts and amps talk.. lol. Thanks for the help

I know it's tough showing up here and asking questions as a beginner. Glad you're here!

The reason everyone keeps harping on "what do you need it to do" is that enough new people have shown up here asking for help that we've seen that there isn't a good "average case" for how much people need to run off their system. Some people consider keeping the Internet and TV and a PC desktop up critical, others just assume they'll of course be able to use a microwave or a hair dryer. Others have a really old fridge that uses 4kWh per day, while mine uses ~1.5kWh per day.

So, step one is to make a list of the things you need to run, then the things you want to run, then the things that would be nice. Then go figure out how much much power (in watt-hours or kilowatt-hours) those things will use per day. I bought a Kill-A-Watt meter and used it to measure the fridge, coffee maker, wife's hair dryer, etc. Averages are fine, I took the fridge measurement over 48hrs to get an average. For the hair dryer, I measured her using it twice and averaged that.

What you're trying to end up with is a "how much power will I use in over X days". Then decide how long you'd want to go without power. That helps you size the battery bank (how many kWh "kilowatt-hours" can you store?) and helps you decide how much charging from solar you need each day (how many watts in panels?)

 

[MichaelK]

so, are the following components a good start to store minimal power?

2=265w panels (I have a total of 6 but don't think i would need all of them to power up 2 batteries at a time)
60A MPPT SCC
2000w 24v inverter
2=24v lifep04 Li Time batteries

I would say no. I'd expect 530W would be good enough for a 12V system, but I'd say a minimum of four of those panels for a 24V system. Batteries perform best when charged at a certain rate. Of course there are exceptions, but here are some VERY broad guidelines for different battery chemistries.

traditional flooded lead-acid: 1/10th to 1/8th of C
sealed AGM: 1/8th to 1/5th of C
Li: 1/5th to 1/4th of C.

So, in your case, you have two 100Ah strings of Li batteries at 24V. That means YOUR "C" is 200Ah at 24V. Looking at the math, a charge rate between 1/5th and 1/4th means...200Ah/5 = 40A to 200Ah/4 = 50A. So, for your particular battery bank, it most likely will be most happy getting 40-50amp of charging. The 60A controller would be fine for that.

Now, if you assume the minimum charging voltage the batteries will see is 25V, it becomes a simple math problem. 40A X 25V = 1000W of panels 50A is 1250W. So really, at least doubling the number of panels you want is the proper way to go.

There's a second way to look at how much solar you need to have, and that is to base it on what your loads are. A good rule-of-thumb that I've used a long time is use the 1.5X to 2X rule. That is for every watt of load you want to support, have at least 1.5X that sized load in solar panels. It's not carved in stone, but over the years it has worked very well for me in real-world applications.

Let's say you want to run a 1 Liter hot water kettle. It consumes 1000W. Using the 1.5X rule, you should have at least 1500W of solar. So, either scale your solar to your battery, or scale your solar to your load, but both are significantly higher than just 530W.

Now, depending on which controller you choose, you have the choice of wiring four panels as either 2S2P, or as a single 4S1P string. The 6415 controller would be able to handle at least three in series, but for four, you need the 6420 controller.

Now, finally, one more way of determining solar is based on your sunhours (sh). That is, the amount of time per day you can expect to get FULL POWER out of your array. If you are located in South Carolina at about 33-34 degrees North, I'd suggest you'll get about 3 sh in December, and maybe 6sh in June, on clear sunny days. You simply multiply your sunhours by your watts of panels to determine how many watthours (or kWh) of power you can make. So, for example, with four panels totaling 1060W, you could make 1060 X 3sh = 3180Wh in December, or ~6.4kWh in June. On cloudy days, with rain, don't expect to get more than maybe 0.5sh per day. That is NOT going to keep a refrigerator running.