Need help with figuring out module wiring- I'm not getting this.

showmeshowme Registered Users Posts: 63 ✭✭

Now that I've got my poles in and one rack up, I'm finally going to have to deal with the 48v system's panel wiring. I plan on using Midnite Solar charge controllers, but have waited until I completely understand the formula involving wiring panels in series, and when to parallel the series' together. I've searched myself blue in the face but can't seem to find a simple (or any) answer to this problem. Here's the set up. I've got 24 LG Neon2 320w modules which will be mounted 12 each on two MT Solar top of pole mounts. I'm running a 48v system (2 Trace Xantrex SW5548 inverters, new in boxes).

  And here is where I get confused. I am under the impression that the series of panels have to add up to the 48v in the system, then will need to be paralleled together from there. My trouble is I don't get how this formula is figured. Maybe someone can educate me. Here are the specs of my modules-

LG320N1K-A5

Vmpp -33.30 v

Impp = 9.52 A

Voc - 40.80 v

Isc10.19 A

Max System voltage - 1000v

Although I've searched everywhere, I still don't understand how to get a panel or panels that are rated at 40.8v open circuit to be run in series for a 48v system. What is it that I'm missing here? Seems like everyone is aware of the answer but me. Thanks for your help.

"Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


Comments

  • AguarancherAguarancher Solar Expert Posts: 315 ✭✭✭
    edited December 2021 #2
    48v is the output of the charge controller to your battery. The input to the CC can be much higher. Midnite has a string calculator on their website. A string is multiple solar panels connected in series.



  • VicVic Solar Expert Posts: 3,145 ✭✭✭✭
    Hi showme,

    Have not heard of "Interstate Workman" batteries.

    The decision on exactly what PV string configuration,  really depends mostly on the nature of the batteries that will be used,  and depending on the max input voltage capability of the Charge Controller.  Your coldest temperatures will be a factor for the string Voc of the PV arrays.

    In general,  with most MPPT Charge Controllers (CCs),  like the MidNite Classics,  you will want PV string Vmps,  around 85 - 100-ish Volts,  when using Flooded Lead Acid batteries,   and CCs with a nominal maximum Voc input of about 140-ish volts.

    As  suggested,  run your PV string configurations,  using the MN String SIzing Tool,  and carefully check the Notes,  at the bottom.

    Let us know how you are doing.    Vic 
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • mike95490mike95490 Solar Expert Posts: 9,572 ✭✭✭✭✭
    Voc is the number to use.   Most charge controllers have a 150V input limit.  40.8 x 3 panels in series = 122.4V 
    Now if you are in an area that gets cold, panel voltage increases a bit, as things get colder.   3 panels in series should be good, but you better run the Midnight String Sizer to make sure a frosty cold morning won't overvoltage the controller and fry it.
    https://www.midnitesolar.com/sizingTool/index.php

    Looks like you are good to -35F with 12 panels per Controller  ( 3s4p )
    You will need a couple of combiners and 8, 150 vDC circuit breakers around 15A  ( look for the MAX SERIES FUSE spec on the panel label )


    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • showmeshowme Registered Users Posts: 63 ✭✭
    edited December 2021 #5

    Thank you very much for this information, everybody! Just to be clear on the batteries, those Interstate's were from a full system I bought, and they were a few years old then. They are similar to Trojan's L16's. Unfortunately, I've had to store them outside in their box, and failed to keep them heated the second year I had them, so they are pretty much unusable I'd say. I plan on using LiFePo batteries in the system, but as with the cc's, I'm still trying to figure out just what I need. I'm retired and 63 years old, so I'd like to get batteries that will last and won't need my constant attention as I age. (I'm in pretty good condition right now, though).

    My problem was 'how do I string panels together that are almost 48v themselves??', so this clears up my misconception of the total voltage. I wasn't clear on the relation between the cc and the amount of voltage input. This now makes sense.

    Which brings me to another question. I've always been confused on the MS cc's, as that I would expect the higher number models to handle higher voltages, but it doesn't seem to work out that way. Or am I mistaken again? I think I'll go back with the information you all have given me and try to figure this out. Any other comments would be greatly appreciated. Lee

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


  • littleharbor2littleharbor2 Solar Expert Posts: 1,694 ✭✭✭✭
    edited December 2021 #6
    The Midnite Solar's higher number models handle higher input voltage. A classic 200, for example will work with up to 200 volts, open circuit. and step down the output voltage to match your batteries. The  thing is with the higher voltage models their max charging current is lower. The one unique thing about the Midnight Solar CC's is their Hyper Voc ability to not be damaged by even higher voltage inputs. They go into Hyper Voc mode to protect the controller from voltages up to the model number plus the nominal battery voltage. If you are running a Classic 200 with a 48 volt battery bank you have a maximum limit of 248 Voc and are still protected from frying your controller.
     In your case you can series wire 4 of you panels and be comfortably in the voltage range with a Classic 200 or 200 SL. It also looks like you can use 3 strings per controller and be slightly over paneled which isn't a deal killer so two controllers will handle all 24 of your panels.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • showmeshowme Registered Users Posts: 63 ✭✭
    Thanks, littleharbor2, that helps. I didn't know if I was to keep the whole line at 48v, or to run them in series to add them, which has been cleared up somewhat per your description. The point is to compound the voltage until just under the number of input volts the charger will handle.  I was completely mixed up before this post. Now I need to land on a specific model and I need to figure what size combiner box I'll need. I just saw a Midnite Solar with 6 series breakers and 2 250v(?) breakers for cc's.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


  • littleharbor2littleharbor2 Solar Expert Posts: 1,694 ✭✭✭✭
    You don't necessarily want to raise the voltage as high as possible. You can series wire 2 or 3 panels and have more parallel strings. Sometimes you use higher voltage for longer runs from the panels to the CC so that you don't have to spend a fortune on heavier gauge wire.
    Typically, the combiner box will mount near your panels and then you can run a single pair of wires from there to the CC or the PV breaker adjacent to the CC. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • showmeshowme Registered Users Posts: 63 ✭✭

    Thanks, again. I didn't mention that I'll be using a temporary garden 'shed' I'm building to house the equipment in until we build our house down at the property next spring/summer. I've poured an 8x8 pad for a small building that sets between the two arrays, which are 30' apart, so to begin with we can power our 5th wheel that is there. After the house is built, we'll transfer the bulk of the equipment up to the house, which will be about 270' from the arrays and shed (at the back of the clearing visible behind the right pole). I'm also trying to figure out what I need for that run, and what to leave in the unheated shed when that happens.

    I plan on mounting combiner boxes either on both poles and join them in the shed, or maybe just running the wires straight to the shed and having a single combiner box there that would be left there after the move. Or is that a bad idea?

    Here are a couple of pics, the 1st is pre-pier pours without the shed slab form yet. The second is what I've got so far on the first array. The MT Solar mount was actually fun to build. But I'm a retired Ironworker, so this is my cup of tea. And to be able to adjust the inclination each month-easily- is just icing on the cake.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


  • showmeshowme Registered Users Posts: 63 ✭✭
    Hey, guys (Aquarancher, Vic and MIke), I checked the MS string sizing tool, and the 150 looks like what I'll be using. Also, thanks for the heads up on the combiners and breakers, Mike. I have to admit, now that I'm passed my initial confusion on volt sums, I'm starting to understand this. My next question is, if anybody is still listening, does anyone have a drawing or picture of a good, clean wiring job of how the array should look? I'm having trouble visualizing how the wires get from the series connection points after leaving the panels' wires. Run them all back to center and head for the pole? Where do the wires enter the conduit enroute to the combiner box? What type clips are best for Iron Ridge XR1000 rails? I don't want to wire it and then find out there's a better, nicer looking way. Here's a pic of the back of my unfinished (until it's wired) array.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


  • PhotowhitPhotowhit Solar Expert Posts: 5,811 ✭✭✭✭✭
    Here's a scary combiner box, All UL equipment rearranged, you can see a little of the wiring in the back ground. This a 20 panels wired in strings of 2, this combiner box uses fuses, and is actually split into 2 arrays going to 2 charge controllers.

    The power center looks a bit like this, though an inverter was added above the ProSine for yard work, until I replaced the Prosine with the Magnum 4024 a couple years ago. This is under the array, the solar array strings come in from behind into the Midnite E-Panel (a breaker box configured for solar)


    Here's a couple closeups of the E-Panel with the wiring direction mapped out, red positive, blue negative;
    As setup this is just a DC breaker box, I added a AC breaker on the unused Din rail (they come with a transfer switch for this Din rail for a generator, I've never used a generator with my systems), and did my Neutral - Ground connection here later.


    BTW-You haven't asked us about grounding connections for the panels yet...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • PhotowhitPhotowhit Solar Expert Posts: 5,811 ✭✭✭✭✭
    I really like stainless steel spring clips to help keep wires orgainized on the back of panels. Not the ones I used, can't recall if there are UL listings for this.

    PHITUODA 150pcs Solar Panel Cable Clips Trailer Wire Clips Stainless Steel 08534  22mm Length

    https://www.amazon.com/dp/B08KRHSPJP/ref=sspa_dk_detail_3

    There will also be 'Lay-in-lugs for your grounding wires, read up before you screw in these lugs, it's a common failing point, I recall something like 40% fail after a few years, even when properly installed! There is a new WEEB(?) system you might look into.

    I believe you want tinned copper, which I'm not seeing on Amazon. Also must use thread cutting SS screws and star(?) washers. Been a while though...

    Ground Lugs lot of 20


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • RCinFLARCinFLA Solar Expert Posts: 1,453 ✭✭✭✭
    edited December 2021 #13
    One other important thing for MPPT controllers is the minimum panel voltage needs to be at least 5 or 6 volts above the maximum battery voltage.

    Most all MPPT SCC are buck switching converters, meaning they only step down in voltage.  They need some input overhead voltage for switcher to operate and overhead voltage for MPPT search algorithm of MPPT controller to verify it has found maximum power point.

    Not having enough PV overhead voltage above battery voltage can result in MPPT controller just dropping back to PWM mode of operation which results in less power output from PV array.
  • showmeshowme Registered Users Posts: 63 ✭✭

    Great information, guys! Thanks very much. Photowit, that's a clean looking set up. I'm impressed with your power center build, too. Thanks for the detailed pics. This helps a lot. I've got a bag of clips from Iron Ridge, but they're plastic and they only mount on the top of the rail and hang to the back of it. Since my modules are laid out in landscape style, they don't give much help as far as crossing horizontally. The ones in your link look easier to route the wires with. I will say those grounding lugs you say are prone to fail are what I'm using. I believe they're IR brand too.

    RCinFLA-thanks for the heads up on that. I'm looking at batteries right now, and will go with LiFePo's although I haven't decided which brand yet. Kilovault and Discovery are the front runners so far.

    One thing I'm trying to get right at this stage is the wiring from the modules to the combiner box, and doing it neatly. I've seen some pretty bad looking pics of 'finished' projects, with wires dangling everywhere, wrapped around boards, etc. After plumbing and wiring half a dozen investment houses over the years, I've gotten kind of anal about routing wires as neatly as possible. Any pics of the backs of arrays out there? It looks to me that with my array, I'll have to homerun wires returning from the outside panels to the center of the rack, then will need to direct them to the conduit entrance which I'm assuming is normally at the top of the pole?? Also, what type of weather head is normally used as the wires enter the conduit at that point.

    Per the question about grounding, I'm finding a lot of information on that. But I will get back on here for expert advice when I get to the point of that, which is the first thing I'm doing. I will ask this- is 10g heavy enough for ground wire, or should it be heavier? Thanks again for all the help and replies. I get on my computer once in the morning and once in the evening, and jump right on this forum to see what's new. (I don't use a smart phone, and there's no signal at the property yet (40 miles away from our house). I'm sort of like a kid in a new playground right now.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


  • mike95490mike95490 Solar Expert Posts: 9,572 ✭✭✭✭✭
    You do realize that much of the power of the top center panel, ( with the shade from mast on it ) will not produce very much power, because of shading.  depending on the panel layout with bypass diodes, it may not contribute anything , or at the most, just 2/3's of rated power.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    I believe the "Mast" is part of the hoisting mechanism for lifting the array into place. The mast/lifting system will be removed and a panel installed in that location (my guess--you can see the cable which in a picture).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    I suggest (and confirm with NEC/local electrical code)--6 AWG minimum for grounding. 6 AWG minimum to manage lightning current, and also "heavy enough" to avoid damage when connecting to exposed ground rod/etc.

    If you have lightning issues in your area--There is a LOT MORE READING required.

    Also need to look at current(s) in system to ensure that 6 AWG is heavy enough for "safety grounding" (i.e., short circuit between a "hot wire" and metal grounded framework/etc.)... For example, if you have a 250 Amp breaker for battery bank, you may need >6 AWG for safety ground (again NEC has details for code requirements).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • showmeshowme Registered Users Posts: 63 ✭✭
    edited December 2021 #18

    Mike- this is an MT Solar rack, which allows me to set the whole thing myself. It's made with a collar that wraps around the 8" poles, and an insert for the top of the pole that then gets a 2x2 square tube with a picking eye set inside of that. A 1 ton chain fall is used to lift the collar up the pole after the rack is built, panels are attached (except for the one the pole goes through), and then the collar is tightened and secured at the top of the pole, after which the last module is added. They're really cool. I built the whole thing by myself at shoulder level. No crane, no ladder (except for the last module), and it took me less than a day working alone to get the first one up. You can see the second one still bundled on it's pallet, on the slab between the array poles. Best thing about it is it has a screw type adjustment handle that will let me adjust the arrays each month for direct sun, and it's easy to turn. Here's a 2 minute animation of what I have-

    Bill- thanks for that information. I had pretty much decided 6g will be what I use, and have been trying to decipher NEC's code's as I go. Thanks for all the input.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


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