diy solar

diy solar

New 40' container power house build.

Put 2 in series. Repeat for a total of seven strings of 2. Then parallel those. "2S7P"
One problem with 7 panels in parallel, connected in series with another 7 panels in parallel, is if some strings were unplugged, current from 7 panels would be forced through fewer panels - that's too much current for the diodes. Or the wires.

There should be fuses or breakers for each string. Here are some ideas:




 
I am getting confused, Original Poster, bought 3 breaker combiner panel, BUT discussion was about 6 breaker combiner boxes.
OP has 7 pairs of PV in parallel.
 
Reading first post, he has 20 panels.
I think he's trying to put in 7 pairs of panels, maybe because that hits wattage limit of charge controller.
But as I said earlier, he could use all of them if at different orientations. So I think 10 strings of 2 panels is good.

 
Mopat and Hedges,

From: Sep 16, 2020
I need an 2S 7P configuration, per Ian delivering 125volts and 42Amps at the charge controller, keeping voltage under the required 145VOC /Vdc.
So my current systems is limited to 14 of my 20 panels, in a 2-Series x 7-Parallel to achieve this maximum panels used.

I need to keep the Controller under 145 volts VOC, each panel is 64.9VOC and 6.46A ISC.
1. As my new path is to create a group of 14 panels, each pair in series, then parallel the 7 strings, which will not fit in my combiner box but only requires one breaker at 63A (70A if Midnight solar made one, they skip from 63A to 80A).
2. The 64.6A ISC x 7 panels = 45.22A. Multiplied by 1.5 for excess per code is 67.83A for a Breaker, which Midnight solar does not sell, and 80A is too large. My question is; At multiplier of 1.4 = 63.08A is that big enough?
3. I assume there is no issue with delivering the 7 strings to a pre-combiner box, with a 8 position bus bar for positive and one for negative. Then feed the single wire into the Midnight combiner box with the breaker and I have met my need to both shut off power and protect the inrush voltage to the Charge Controller. Is this a safe assumption?
4. I suppose can put 7 breakers in a 6 breaker box if necessary, they simply clip to a DIN rail, I can have a 7 breaker bus bar cut out on a water jet if necessary, like this 8 position bar.
1601164725143.png
 
Mopat and Hedges,

From: Sep 16, 2020
I need an 2S 7P configuration, per Ian delivering 125volts and 42Amps at the charge controller, keeping voltage under the required 145VOC /Vdc.
So my current systems is limited to 14 of my 20 panels, in a 2-Series x 7-Parallel to achieve this maximum panels used.

I need to keep the Controller under 145 volts VOC, each panel is 64.9VOC and 6.46A ISC.
1. As my new path is to create a group of 14 panels, each pair in series, then parallel the 7 strings, which will not fit in my combiner box but only requires one breaker at 63A (70A if Midnight solar made one, they skip from 63A to 80A).
2. The 64.6A ISC x 7 panels = 45.22A. Multiplied by 1.5 for excess per code is 67.83A for a Breaker, which Midnight solar does not sell, and 80A is too large. My question is; At multiplier of 1.4 = 63.08A is that big enough?
3. I assume there is no issue with delivering the 7 strings to a pre-combiner box, with a 8 position bus bar for positive and one for negative. Then feed the single wire into the Midnight combiner box with the breaker and I have met my need to both shut off power and protect the inrush voltage to the Charge Controller. Is this a safe assumption?
4. I suppose can put 7 breakers in a 6 breaker box if necessary, they simply clip to a DIN rail, I can have a 7 breaker bus bar cut out on a water jet if necessary, like this 8 position bar.
View attachment 23760

"So my current systems is limited to 14 of my 20 panels, in a 2-Series x 7-Parallel to achieve this maximum panels used."
Ah, but as I keep saying, you can hook up 20 panels, 2S10P, and not exceed wattage or current that would come from 12 or 14 panels, 2S6P or 2S7P.
Just aim the 10 strings in various directions. If they are at an angle to each other, area presented to the sun at any given time is less, so amps and watts is less. But earlier and later in the day, it will make more power than a single orientation would. Spreads your production over the day.

"but only requires one breaker at 63A"
Needs one fuse/breaker per string. That is what the "maximum fuse" spec on your PV panel label is for. If there is a short in a panel, the other 6 strings dump 35A into it and melt something. (That's why we like like high voltage series strings and no more than two strings, e.g. 7S2P, if our charge controller can take that high a voltage. All my stuff is designed around 600V absolute max. Look Ma! No Fuses!)

"My question is; At multiplier of 1.4 = 63.08A is that big enough?"
The idea was to get 1.25 x continuous current to avoid nuisance trips. Cold day, current can be higher than label. But your charge controller won't be operating panels at Isc, rather at Imp. Worst that can happen is breaker trips, so you should be fine. If we were sizing wire to operate with no breaker, then would want to use worst-worst case figures.

6 awg rated 90C has ampacity 75A (in bundle of 3), or 105A (single conductor in free air.) So I don't think you really need a breaker on that size wire.

"I suppose can put 7 breakers in a 6 breaker box if necessary, they simply clip to a DIN rail, I can have a 7 breaker bus bar cut out on a water jet if necessary, like this 8 position bar."
That is the thing to do (the breakers on DIN, at least.) Lots of commercial parts are tinned aluminum. I think copper would be the way to DIY.

"water jet"
You kids with your newfangled toys! I grew up with an arc welder and oxy-acetylene torch. Want to see how I get a 1.25" nut off my tractor when I don't have enough air and the right wrench to do it?
I need to make a breaker panel cover with a rectangular cutout for DIN transfer switch. Water jet would be a way if I had access. I don't have a neat way to make rectangular inside cuts, just round holes with a Greenlee Slug Buster.
Such a busbar I'd probably drill and chop with bandsaw. But your CNC water jet is going to be more steady than me with bandsaw. I don't even have access to a Rotex punch like I used in school. Picked up a cheap used HF drill/mill lathe, but the vertical spindle is stiff.
 
OK, sounded like you bought a Midnight Solar 3 breaker combiner box.
So feed it with 3 pair and 4 pair;
14 x 327 = 4578 watts That SPF3000TLLVM-48P is rated 4500, it will be fine.
You can use their 63 amp Over Current Protection Device on each string as a PV disconnect.
MC4's can combine the (3pair, 4pair) strings; they'll be under 30 amps. 10AWG fine to combiner box.
 
So just get short MC cables and cut in half to make pigtails for the combiner.

Each string should have a fuse. You can put MC4 fuse holders in line.

 
My Combiner box is a re-purposed 125a service panel with a new Din rail and two 63A breakers installed with the buss bar pictured in my response above on 8/26 with 8 connections for breakers. (I'll attempt adding photos later). Made a custom breaker cover plate, using 22 gauge galvanized, and had the hole for the 7 breakers cut out with the water jet, Just $10 for labor. Nice clean hole with great square corners, (See blue tape in pic.) No need for an oxy acetylene torch here.. ;#D
I'll lay out two strings of two panels near these boxes on my patio for testing/mock up tomorrow. I will say the cabling has been challenging with all the 2AWG and 6AWG connections and finally determining how to attach safety disconnects and though panel connectors, proper welding wire sheathing etc. None of the 3/8" ends, butt connectors, orange sheathing etc are available locally, even Red 2AWG welding cable is non existent here in Lake Havasu.

The Midnight Sun 3 breaker box is now mounted on the steel lid of the battery box/ power wall, as it was too small for the seven, 10AWG wires and all the combining. This little box now supports, an 80A double breaker that accepts the 2 AWG wire directly. (My Growatt supports up to 80A charging).

Tomorrow I mig weld the new flat panels created to flatten the box top to allow for the small Midnight Solar 3 breaker box to provide my battery shut off on the battery case.
 

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Any suggestions on "Near free ware" for creating visual image of the flow of PV to Charger/Controller, with batteries, switches and disconnects? Something like this one? Interactive-Solar-Wiring-Diagram-Facebook-Image-1024x538.jpg
Note: On Youtube I found someone posting several diagrams, he listed a service to draft up one for you, but at $375,/hr that is about three times what my back surgeon makes at Stanford University Hospital.
 
We are starting this off grid project with the following equipment just received:

Parts, starting place;
* 40' container located at 6800' Summer 97 degrees, Winter 10 degrees.
* Growatt 3000w 120v output, 48vdc input from Watts247
* 20 solar panels, 327w used Sunpower
* 800KW Lithium, 48v BMW batteries, from Battery hookup
* 2awg cables with disconnect below the panel, 60w breakers on each of the two battery packs to de-rate them a bit.
* Plan to string second Growatt 3000 to add input charging and run the AC on camper next summer.

Loads:
* Small RV Camper, one AC unit, microwave
* Charging battery powered tools
* Laptop

Unkowns:
How to group and connect the 327w solar panels to not exceed voltage limitations.

* 80A MPPT / 6.5Amps per solar panel + 12.3 panels.

Growatt's limitations.
* 48v
* Input 80A MPPT
* Input 40 from Generator

Solar panels limitations;
* Rated power max 327 Watts
* Voltage 54.7 Volts
* Current Input 5.98 Amps
* Open circuit VOC 64.9 Volts
* Max series fuse 15 Amps

** By my calculations, I can only attach 12 panels to the Growatt 3000w. Even if I chose the 6000w unit I gain 220v AC but can only attach some 15 of my 327w panels. I am not sure which is the better option.
I bought these 327-watt panels and also found to be limited to 2s configuration then parallel them in a combiner box as I also bought outback 80 amp flexmax scc. seems like I am on a similar path as you. i built an insulated 8x8 shed for batteries inverters and scc. good luck with all.
 
the shipping container is a great time saver I think. as I am building - almost done building an 8x8 insulated wood frame solar power shed. how did you insulate the shipping container? I may go with one of them on my next solar build.
 
Ever consider pointing your pv in different directions ? Currently I have 1 array optimized for summer. 1 for mornings & I am about to install the one thats ideal for winter. I am doing it this way for a few reasons. The plan is to have 5 arrays. East, west, summer, winter & main. If I just went with 1 main I would have to deal with snow to get going after storms. On those days that start & or end with sun but are cloudy all day, got power. My winter array wont collect as much snow & will be easier to clear than the summer array.

My goal is to have a 200amp panel system that should need a 800ah battery. With only a 200ah battery. I'll be adding wind also. By having pv pointed all around & wind I'm trying to down size my battery to 1/4 to recommend size.

As long as you add these anti back flow devices that are like $12 on ebay you'll be okay
 
Ever consider pointing your pv in different directions ? Currently I have 1 array optimized for summer. 1 for mornings & I am about to install the one thats ideal for winter. I am doing it this way for a few reasons. The plan is to have 5 arrays. East, west, summer, winter & main. If I just went with 1 main I would have to deal with snow to get going after storms. On those days that start & or end with sun but are cloudy all day, got power. My winter array wont collect as much snow & will be easier to clear than the summer array.

My goal is to have a 200amp panel system that should need a 800ah battery. With only a 200ah battery. I'll be adding wind also. By having pv pointed all around & wind I'm trying to down size my battery to 1/4 to recommend size.

As long as you add these anti back flow devices that are like $12 on ebay you'll be okay
The key is regulating battery charge current to optimal value.
How will you do that? Link to "anti back flow device"?

I get away with undersize battery and oversize PV with AC coupled SMA Sunny Boy and adjustable battery charge current of Sunny Island.
Some other brands with DC coupling can do the same (Victron?)

I'm also in the process of spreading out array orientations. Started out all 2:00 PM due to previous time of use rates. I'll have multiple angles to deliver more Wh/day while limiting peak watts. Off-grid, same idea works to reduce battery cycling.
 
The key is regulating battery charge current to optimal value.
I use a Midnite 250. I guess it has all that figured out.

anti back flow

I get away with undersize battery and oversize PV with AC coupled SMA Sunny Boy and adjustable battery charge current of Sunny Island.
Some other brands with DC coupling can do the same (Victron?)
TBH not sure. I haven't had any issues with too much power.

Something to do with wind is a clipper that deals with over power caused by wind. But apparently solar is different & thats not a issue.
 
OK, anti backflow is an ideal diode, may be useful in some cases such as parallel PV strings. My math has said power lost from normal diode in conducting direction is similar to power lost leaking back into a shaded string of panels. Ideal diode would have less loss. A few other places it might be a benefit.

Midnight Classic 250?


So that regulates voltage and delivers up to 63A.
What is the maximum charge rate your battery wants to see? If 63A is fine, no problem.
But is that a 200A lithium battery, or AGM? AGM may want only 20A or 40A charge, and 63A would be too much.
Now what if your panels and charge controllers can deliver 200A? (e.g. three Midnight Classic 250, 189A total output.)
That would be way too much continuous current for a 200 Ah battery.
But, you might want to run a 5kW inverter with the power coming from PV.

So ideally, charge controller output would go up when inverter draws power, go down when it doesn't, maintaining constant 40A charge current to battery.
That is what one of the equipment families can do, I'm told. (I think it was Victron) It would have digital communication between inverter and charge controller.
My SMA does that by altering AC frequency as a way to communicate.

That Midnight charge controller does have an optional shunt, which could be used to measure battery current. The question is whether it has software/settings so it can regulate battery current, while supplying variable current to loads such as inverter.

If you're planning to have excessive size PV and undersize battery, you need to consider that avoid cooking the battery.

For wind, the clipper is probably a shunt load to serve as a brake, and keep wind turbine from overspeeding or delivering excessive voltage.
 
Midnight Classic 250?
Correct.

What is the maximum charge rate your battery wants to see?
150A BigBattery

Now what if your panels and charge controllers can deliver 200A? (e.g. three Midnight Classic 250, 189A total output.)
That would be way too much continuous current for a 200 Ah battery.
But, you might want to run a 5kW inverter with the power coming from PV
I've got a long story system. Learning curve. Going to sell off my battery, MC250 & a 36v 3000w inverter & replacing it with 3 more MPP Solar all in ones 3000w & a 280ah 48v battery I am going to build with the nice cells.

If you're planning to have excessive size PV and undersize battery, you need to consider that avoid cooking the battery.
When I have all those MPP Solar all in ones hooked up they can regulate the charging amperage. Its a setting. You can set max A for both PV & your AC charging source. I am glad you pointed this out tho.

Those back flow deals are to prevent fire. I use used pv. So cheep mounting them cost more than the pv it self. Santan is pretty sweet. I got 2 pallets of 250w & 265w pv for under $3k.
 
Consider fuses, not just the backflow preventer ideal diodes, if you have many PV strings in parallel. Being so simple, they would be more trustworthy than no-name electronics.

I bought pallets from Santan as well. Also a good deal, but went with a premium brand at a different price point.
 
Consider fuses, not just the backflow preventer ideal diodes, if you have many PV strings in parallel. Being so simple, they would be more trustworthy than no-name electronics.

I bought pallets from Santan as well. Also a good deal, but went with a premium brand at a different price point.
Oh ya I have breakers & fuses. Want to be on all breakers but will need to re wire stuff.
 
My Combiner box ... with the buss bar ... with 8 connections for breakers. .
Are those polarized breakers?

I recently figure out that are not able to interrupt current flowing in the reverse direction due to a fault causing a short in one string. And that was the reason for having breakers.

Solution is either diodes so there isn't any backfeed, or ganging all the breakers together so interrupting of current is accomplished by the ones conducting in correct direction.
 
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