Beginner, need assistance

[Stanman17]

Hello y’all I’m new to solar, I think I’m on track but may need confirmation or correction. I have 10 100watt solar panels, standard probably 20v 5a each. I’ve been going back and forth on series wiring 5 then the other 5 separately, taking the 2 neg and 2 pos from all the panels and running them into a combination box grounded before the charge controller. So would that work? Or should I do 5 parallel groups of 2 panels series together. Any advice would help, one result would be 40v 25a leaving the combination box, the other result 100v 10a leaving the combination box to the renogy 100a charge controller. 10 gauge wiring for all of this okay as well?

Another question sorry, I have 6 12v renogy 100ah batteries in parallel, should I connect the pos and neg from charge controller AND inverter on the same pegs from each end? Or alternate where one connects. Thank you so much, I have some concerning questions just wanna make sure I set my first solar array up right for efficiency. Any feedback would be greatly appreciated!

 

[BentleyJ]

The voltage and amperage rating of the Charge Controller is the determining factor in how to connect the PV panels, series vs. parallel. Charge controllers range from 100V up to 600V DC. Higher voltage requires more expensive electronic components in the Charge Controller

From a wiring consideration, higher voltage PV strings are favorable as it reduces the number of circuits (may eliminate the need for combiner boxes) and lower currents (because higher voltage gives equivalent Watts with lower amps) allow the use of smaller ga less expensive wire.

Victron offers a full line of charge controllers. That would be a good place to start looking.

 

[Mattb4]

Concerning your Array setup. Would need to know panels specifications for Voc, Vmp, Isc and Imp. Also would need to know your charge controllers specifications for Voc and max current if it has one. Also it could help if you could give some idea if you have any shading issues.

For 6 batteries in parallel I would recommend a bus bar setup. You could even do this with 3 in parallel to bus bar (pos and neg to bar from battery 1 pos and 3 neg respectively) the other 3 parallel connected to bus bar in the same fashion with equal length cables. Make sure that the output cables can handle the amperage. From the Bus bar you would have connections for your inverter and the SCC. .

 

[MichaelK]

I think you are making some serious design mistakes. Starting out, the fact that you are buying 10 12V panels suggests that you did not to the amount of research you should have. You pay a price premium for 12V automotive panels, and you would have saved a lot of money if you had gotten larger high-voltage residential panels. You might save a bit of money going 12V with a PMW controller, but the breakeven point is about 300W. Since you already have an MPPT controller, you are simply wasting money.

Although not manditory till you have three or more strings, it's a best practice to either fuse or breaker each individual solar string. I like breakers, ever for just two strings, because I can just flip of a string if I want to do any troubleshooting.

Six parallel strings of small batteries is a mistake. If you need 600Ah of storage, you should have purchased 600Ah batteries. This is what I myself have to make ~600Ah string.

4 CS 17P | Rolls Battery

www.rollsbattery.com

That Renogy controller has a 150V limit, doesn't it? 5 in series is clearly a better choice. I think thinking about having pairs of panels in series is just another example of inadequate research before buying.

Lastly, if you need to power stuff that needs 600Ah of storage, you most likely would have been better off going with a higher system voltage than 12V.

 

[Stanman17]

I think you are making some serious design mistakes. Starting out, the fact that you are buying 10 12V panels suggests that you did not to the amount of research you should have. You pay a price premium for 12V automotive panels, and you would have saved a lot of money if you had gotten larger high-voltage residential panels. You might save a bit of money going 12V with a PMW controller, but the breakeven point is about 300W. Since you already have an MPPT controller, you are simply wasting money.

Although not manditory till you have three or more strings, it's a best practice to either fuse or breaker each individual solar string. I like breakers, ever for just two strings, because I can just flip of a string if I want to do any troubleshooting.

Six parallel strings of small batteries is a mistake. If you need 600Ah of storage, you should have purchased 600Ah batteries. This is what I myself have to make ~600Ah string.

4 CS 17P | Rolls Battery

www.rollsbattery.com

That Renogy controller has a 150V limit, doesn't it? 5 in series is clearly a better choice. I think thinking about having pairs of panels in series is just another example of inadequate research before buying.

Lastly, if you need to power stuff that needs 600Ah of storage, you most likely would have been better off going with a higher system voltage than 12V.

Yes sir I may have made some design mistakes, what would you recommend I do? Should I attempt to wire solar panels in 24v, and the six batteries in 24v and buy a different inverter? The inverter I bought is renogy 3000watt 12v, so that’s why I’ve been holding onto 12v system but if it’s possible to wire everything differently for 24v my renogy 100a charge controller would be able to handle it I believe. I wanted to purchase more future proof, I messed up badly with the inverter though, my ignorance.

If I wired the panels in pairs of 2, the combiner box would have fuses for each of the 5 connections in correct? (Eco Worthy 6 sting input) So wouldn’t that be a better bet than 5 in series only having two inputs to the combiner box? Like you said you like to put breakers or fuses on each panel or pair if possible? I apologize I know I’m a noob I’m trying to understand before I make any mistakes wiring stuff together, make any last minute changes if I can to return the inverter to change to a 24v system. Thank you for your input MichaelK.

 

[hwy17]

Although not manditory till you have three or more strings, it's a best practice to either fuse or breaker each individual solar string.

There is no purpose in fusing 1 or 2 strings.

 

[Stanman17]

Concerning your Array setup. Would need to know panels specifications for Voc, Vmp, Isc and Imp. Also would need to know your charge controllers specifications for Voc and max current if it has one. Also it could help if you could give some idea if you have any shading issues.

For 6 batteries in parallel I would recommend a bus bar setup. You could even do this with 3 in parallel to bus bar (pos and neg to bar from battery 1 pos and 3 neg respectively) the other 3 parallel connected to bus bar in the same fashion with equal length cables. Make sure that the output cables can handle the amperage. From the Bus bar you would have connections for your inverter and the SCC. .

No shading issues, will be propped in an open field. Voc of single solar panel is 21.6V, Vmp 17.9V, Isc 6.24A, Imp 5.71A. The charge controller can handle 150V input, max 100A. It’s the renogy 100A. Bus bar is the part of the equation I’ve been missing, thank you so much for your help on that front sir. Going to do more research on the steps you provided. Thank you Mattb4.

 

[Stanman17]

Hello y’all I’m new to solar, I think I’m on track but may need confirmation or correction. I have 10 100watt solar panels, standard probably 20v 5a each. I’ve been going back and forth on series wiring 5 then the other 5 separately, taking the 2 neg and 2 pos from all the panels and running them into a combination box grounded before the charge controller. So would that work? Or should I do 5 parallel groups of 2 panels series together. Any advice would help, one result would be 40v 25a leaving the combination box, the other result 100v 10a leaving the combination box to the renogy 100a charge controller. 10 gauge wiring for all of this okay as well?

Another question sorry, I have 6 12v renogy 100ah batteries in parallel, should I connect the pos and neg from charge controller AND inverter on the same pegs from each end? Or alternate where one connects. Thank you so much, I have some concerning questions just wanna make sure I set my first solar array up right for efficiency. Any feedback would be greatly appreciated!

This is what I have mapped so far, going to be making changes shortly. Any input be greatly appreciated, I apologize I know I’m a noob, but I need to learn and understand, I am open to criticism.

 

[Mattb4]

10 panels at 21.6V therefore would need to be connected 2 strings of 5 series connected to your combiner box. This will give you 108Voc and a current of 11.42a. Depending on run length to combiner box (not required for 2 strings but handy) you could use 12awg.

Be aware that the 100a SCC rating is maximum battery charge current.

 

[MichaelK]

Just to be very clear first, is this your charge controller?

I don't want to give you the wrong advice based on the wrong electronics? With a limit of 150V, there is not a very good reason not to put 5 panels in series to make 5A 100V DC panel strings. I would however stop buying 12V panels completely. At 1W/$ they are grossly overpriced. Purchase larger, high-voltage residential panels instead. They may be commonly referred to as "grid-tie panels". Shop locally for those instead of mail-order. Shipping is the killer in solar panel pricing. With cash and carry purchases, you should be getting new panels for 2-3W/$. Maybe 4-5W/$ for used panels.

Renogy does not market the best stuff. Used quality panels I purchased off of Craigslist outperformed new Renogy panels. I am not impressed with their batteries either. With six of them, you are kind of stuck? As a general rule, the more parallel strings of batteries you have, the more poorly balanced they become. You could make a 24V system, with 3 parallel strings, but I think even 3 is too many, but of course not as bad as six. You could make a 48V system with four of them in series, but you are stuck with two extra batteries. One alternative is to buy two more of those batteries and make a 4S2P battery bank. However, I loathe the thought of recommending the purchase of more Renogy batteries. So, maybe a 3S2P 24V system is the best alternative you have.

If you want to buy more panels, first remember the two following mantras.

1) In series volts add, while amps stay the same. In parallel amps add, while volts stay the same.

2) When mixing panels in a series string, any voltage can be paired but amperage must be within 5%. When mixing panels in different parallel strings, any amperage can be paired, but voltage must be within 5%.

If you want to buy additional panels in the future, and you already have five 20V panels wired in series for 100VDC, all you need to do is match any other panel string to the same voltage (mantra 2, sentence 2). Shop for 60-cell grid-tie panels with a Vmp of ~33V. Three of those in series would give you the 99-100VDC to match up with the strings you already have. Actually, any voltage between 95-105V is going to be perfectly fine.

Then replace the 12V inverter with a 24V one. There are better choices then Renogy. What kinds of loads will you need to support. Lights, TV, computer, and a frig is easy. Big power tools, or anything with a big electric motor that starts under load has what's called a "starting surge", which is typically 3-5X the documented power draw, for just 500 milliseconds or so.

Read the fine print of the inverter you chose to buy. Ignore how MUCH they can surge. Pay close attention to how LONG they can surge. The cheaper high-frequency transformerless inverters typically can surge for less than 1 AC cycle, or <16 milliseconds. Quality transformer-based inverters can surge for between 5-60 seconds (not milliseconds), and are perfect for big power tools.

For my workshop, I power that with Schneider's Conext 4024 inverter. I've run a cement mixer, 1.6hp air-compressor, and a 7" saw, all at the same time, without the inverter blinking! It does however cost 3X the price of lessor inverters, but it can run 3X more stuff. You get what you pay for! It also puts out split-phase 120/240VAC, and has a built-in generator charging circuit.

 

[MichaelK]

There is no purpose in fusing 1 or 2 strings.

I disagree. Although there is no code requirement for adding a breaker, I would breaker even just two strings. You never want to disconnect a solar string in the daytime because of the threat of arcing. If you need to troubleshoot a problem string, it's safer to flip a breaker to first cut the current.

 

[hwy17]

I disagree. Although there is no code requirement for adding a breaker, I would breaker even just two strings. You never want to disconnect a solar string in the daytime because of the threat of arcing. If you need to troubleshoot a problem string, it's safer to flip a breaker to first cut the current.

1 or 2 strings can't generate enough current to trip an OCP like a fuse or breaker, so there is no purpose in the OCP function.

As for disconnecting, that's a requirement for a disconnect, the IMO disconnect is a popular one. Some people decide for themselves that a breaker is a convenient or affordable substitute for an IMO or other plain disconnect, but it's purpose there is not as an OCP.

No matter what your disconnect is: IMO, Breaker, or just unplugging an MC4, in all cases you would want to disable the charge controller or inverter first, so that current is not flowing when you disconnect, and therefore it won't arc.

 

[Stanman17]

Just to be very clear first, is this your charge controller?
View attachment 205301
I don't want to give you the wrong advice based on the wrong electronics? With a limit of 150V, there is not a very good reason not to put 5 panels in series to make 5A 100V DC panel strings. I would however stop buying 12V panels completely. At 1W/$ they are grossly overpriced. Purchase larger, high-voltage residential panels instead. They may be commonly referred to as "grid-tie panels". Shop locally for those instead of mail-order. Shipping is the killer in solar panel pricing. With cash and carry purchases, you should be getting new panels for 2-3W/$. Maybe 4-5W/$ for used panels.

Renogy does not market the best stuff. Used quality panels I purchased off of Craigslist outperformed new Renogy panels. I am not impressed with their batteries either. With six of them, you are kind of stuck? As a general rule, the more parallel strings of batteries you have, the more poorly balanced they become. You could make a 24V system, with 3 parallel strings, but I think even 3 is too many, but of course not as bad as six. You could make a 48V system with four of them in series, but you are stuck with two extra batteries. One alternative is to buy two more of those batteries and make a 4S2P battery bank. However, I loathe the thought of recommending the purchase of more Renogy batteries. So, maybe a 3S2P 24V system is the best alternative you have.

If you want to buy more panels, first remember the two following mantras.

1) In series volts add, while amps stay the same. In parallel amps add, while volts stay the same.

2) When mixing panels in a series string, any voltage can be paired but amperage must be within 5%. When mixing panels in different parallel strings, any amperage can be paired, but voltage must be within 5%.

If you want to buy additional panels in the future, and you already have five 20V panels wired in series for 100VDC, all you need to do is match any other panel string to the same voltage (mantra 2, sentence 2). Shop for 60-cell grid-tie panels with a Vmp of ~33V. Three of those in series would give you the 99-100VDC to match up with the strings you already have. Actually, any voltage between 95-105V is going to be perfectly fine.

Then replace the 12V inverter with a 24V one. There are better choices then Renogy. What kinds of loads will you need to support. Lights, TV, computer, and a frig is easy. Big power tools, or anything with a big electric motor that starts under load has what's called a "starting surge", which is typically 3-5X the documented power draw, for just 500 milliseconds or so.

Read the fine print of the inverter you chose to buy. Ignore how MUCH they can surge. Pay close attention to how LONG they can surge. The cheaper high-frequency transformerless inverters typically can surge for less than 1 AC cycle, or <16 milliseconds. Quality transformer-based inverters can surge for between 5-60 seconds (not milliseconds), and are perfect for big power tools.

For my workshop, I power that with Schneider's Conext 4024 inverter. I've run a cement mixer, 1.6hp air-compressor, and a 7" saw, all at the same time, without the inverter blinking! It does however cost 3X the price of lessor inverters, but it can run 3X more stuff. You get what you pay for! It also puts out split-phase 120/240VAC, and has a built-in generator charging circuit.

Yes that is my charge controller sir. I'm homesteading with a shipping container and 30amp camper, I understand the longevity and max power something like the Schneider's Conext 4024 inverter offers but this is my first solar attempt and $1,500 on an inverter is a little out there for me but I assume I asked for it being unknowledge on getting too future proof with the Renogy 100A charge controller. Our main concern we're going after is fridge/freezer, light hot water heater usage, light AC/Heater usage, mostly just lights and alternating things being on, it's a camper anyways we can't run everything at once anyways and heavy tools needing power isn't a necessity of ours either. Maybe power a deep freezer, water pump, and small heater in shipping container. It will probably be a while before we upgrade more solar panels so I don't see that in our cards anytime soon. So with our needs should I go 24V system or stay 12V? Since I have an idea on how to wire the solar panels in, use pos and neg bus bars to split up the 6 batteries into groups of 3? Is there anyway to wire the 6 batteries to work running 12V? Or should I convert the wiring and alter the whole system for 24V now and replace the inverter I bought with a 24V one? Any recommendations on a 24V inverter for our semi-light needs? Thank you so much for your input MichaelK, I really appreciate it.

 

[Stanman17]

10 panels at 21.6V therefore would need to be connected 2 strings of 5 series connected to your combiner box. This will give you 108Voc and a current of 11.42a. Depending on run length to combiner box (not required for 2 strings but handy) you could use 12awg.

Be aware that the 100a SCC rating is maximum battery charge current.

Thank you Mattb4, genuinely appreciated your feedback sir.

 

[robbob2112]

Just a note - not related to the setup - You can use draw.io to make diagrams - it is free and simple to use if you just watch a 15 minute video on getting started.

 

[Stanman17]

Hello everybody, do you guys think this will work or no? I'll buy bus bars and 24V inverter. Does anyone have any advice on more fuses to place, etc. Hope I finally got it lol I really appreciate all the feedback everyone, thank you so much. I hope I'm getting there.

 

[Mattb4]

Looks like your batteries are wired 3S2P that makes them 36v. For 24v you would wire 2S3P.

 

[Stanman17]

Looks like your batteries are wired 3S2P that makes them 36v. For 24v you would wire 2S3P.

Okay extra fuse for that third pos, larger bus bars. Anything else wrong? Thank you Mattb4, I appreciate it.

 

[MichaelK]

Our main concern we're going after is fridge/freezer, light hot water heater usage, light AC/Heater usage, mostly just lights and alternating things being on, it's a camper anyways we can't run everything at once anyways and heavy tools needing power isn't a necessity of ours either. Maybe power a deep freezer, water pump, and small heater in shipping container.

OK, here is where an itemized list of your items, and their wattage needs, becomes very important. Lights and a TV are easy, you are working with items that draw dozens of watts at most. Things like the frig or freezer may draw hundreds of watts, and water heating elements and some water pumps may draw thousands of watts. One of the most common failures I see on this site is people throwing together a system with no firm idea of how much power they need, or how much power they can actually produce. So, make that itemized list FIRST!!!

So with our needs should I go 24V system or stay 12V? Since I have an idea on how to wire the solar panels in, use pos and neg bus bars to split up the 6 batteries into groups of 3? Is there anyway to wire the 6 batteries to work running 12V? Or should I convert the wiring and alter the whole system for 24V now and replace the inverter I bought with a 24V one? Any recommendations on a 24V inverter for our semi-light needs?

Matt made a good call, it looks like the batteries are wired three in series with two parallel strings. As he says, that won't work. You want three parallel strings of two batteries in series, not two parallel strings of three batteries in series to make your 24V bank.

One thing your drawing doesn't illustrate is the wire you will actually use to connect each component? You want to make sure the wire is thick enough to safely carry the number of amps you are pushing through it. Here's a chart that can help...

From the solar strings to the combiner box, just 10 gauge copper is fine. From the combiner to the controller, maybe at least 8-6 gauge, and from the controller to the batteries, 4 gauge. The wire between the batteries and the inverter needs to be the biggest. That's what's carrying the most amps. With say a 3000W inverter, with a battery bank at 25V, you'll be pulling >120 amps to make that 3000W. That's 0 gauge minimum. For my own 4000W inverter, I used 000 gauge, and 0000 for my 6848 inverter. You might find cheaper roll-end remnants at the HomeDepot wire isle. Copper wire is EXPENSIVE. You want to buy enough to make your connections, but you don't want to buy too much because it's so expensive. Make sure you get a good crimp on the ends. Loss crimps result in over-heated connections.

I got the tier-1 inverter because of my power tools, which is powers phenomenally well. If you aren't running cement mixers though, you can get by with a cheaper high-frequency inverter. Just make sure it's sine-wave so your electric motors are protected.

Pay close attention to the watts needed for your water heater. I suspect that will be your largest single load. I'd get an inverter that can handle 2X what the water heater draws. That means, if the element draws 1500W, get a 3000W inverter.

 

[Stanman17]

OK, here is where an itemized list of your items, and their wattage needs, becomes very important. Lights and a TV are easy, you are working with items that draw dozens of watts at most. Things like the frig or freezer may draw hundreds of watts, and water heating elements and some water pumps may draw thousands of watts. One of the most common failures I see on this site is people throwing together a system with no firm idea of how much power they need, or how much power they can actually produce. So, make that itemized list FIRST!!!

Matt made a good call, it looks like the batteries are wired three in series with two parallel strings. As he says, that won't work. You want three parallel strings of two batteries in series, not two parallel strings of three batteries in series to make your 24V bank.

One thing your drawing doesn't illustrate is the wire you will actually use to connect each component? You want to make sure the wire is thick enough to safely carry the number of amps you are pushing through it. Here's a chart that can help...
View attachment 205508
From the solar strings to the combiner box, just 10 gauge copper is fine. From the combiner to the controller, maybe at least 8-6 gauge, and from the controller to the batteries, 4 gauge. The wire between the batteries and the inverter needs to be the biggest. That's what's carrying the most amps. With say a 3000W inverter, with a battery bank at 25V, you'll be pulling >120 amps to make that 3000W. That's 0 gauge minimum. For my own 4000W inverter, I used 000 gauge, and 0000 for my 6848 inverter. You might find cheaper roll-end remnants at the HomeDepot wire isle. Copper wire is EXPENSIVE. You want to buy enough to make your connections, but you don't want to buy too much because it's so expensive. Make sure you get a good crimp on the ends. Loss crimps result in over-heated connections.

I got the tier-1 inverter because of my power tools, which is powers phenomenally well. If you aren't running cement mixers though, you can get by with a cheaper high-frequency inverter. Just make sure it's sine-wave so your electric motors are protected.

Pay close attention to the watts needed for your water heater. I suspect that will be your largest single load. I'd get an inverter that can handle 2X what the water heater draws. That means, if the element draws 1500W, get a 3000W inverter.

I ordered a 4000watt inverter, the water heater is something we won’t use all the time, it’s small only 3gal. With the solar panels I have and not getting any more currently, we will definitely need a 5000 watt predator dual fuel generator for some nights maybe, cloudy days, winter for sure for keeping stuff heated. I know the solar may not be able to power it all but we’re going off grid so propane power/gas power help is going to be needed for certain instances I’ll be working on that today. Weeks ago I wrote a list of what the AC/heat/microwave/fridge pull. I have an idea about what stuff pulls, I just don’t have that much money to spend $6000 or something to be able to be on solar only, that may be in a few more months or next year. Thank you so much for your guys help, your last reply really gave me all the info I needed to be honest, for wiring and fixing the batteries. Thank you so much for your help MichaelK, Mattb4. I think I got it now, you guys helped so much, words can’t describe how much you guys saved me in understanding all of this. If I have any more issues I’ll comment on the post!