Sanity Check Please

vdub

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May 31, 2021
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I have a question concerning fuses; both how many amps and placement. This diagram is my system. I have 58 foot run from the panels, through the forest, to the solar controller. I really want to get this right as I don't want to burn down my cabin or the forest.

I'm enclosing the 58' run inside pvc pipe and burying it about 14" deep. That should keep the squirrels from molesting the wire and shorting it out. I'm thinking a single 20A fuse at point E on the diagram is all I need. But maybe a couple 15A fuses at points C and D, too? Or should I move the 20A fuse closer to the MPPT at point F? Or, should I have a 20A fuse at both points E and F?

I've enclosed an image of the specs for the panels, as well as the MPPT specs. These panels are the used $50 unbranded panels that Will found and recommended. They are all working perfectly near as I can tell, of course, I'm only measuring voltage at this point. Even in overcast weather, I'm getting 30V on each panel.

In addition to my question on the fuse, what kind of kill switch do I need? I can't believe I have to spend $67 on Amazon for a stupid switch, however, it will have 60V passing through it. Isn't there something cheaper?

If someone (or maybe a couple people smarter than me) could check this diagram against the various labels and capabilities and tell me if it makes sense, I'd really appreciate it. Please, in particular, check the MPPT label against what I will have going into it. I think I am understanding the input correctly and not exceeding the limits, but not absolutely positive.

Really appreciate any help I can get before connecting things up. Thanks!
 

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Jgb3

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E53FC0DD-E335-41D9-BDED-AE3B5F2F6BA6.png
AliExpress
And I would put 2 15 amp fuses at c and d but I’m no expert
 

vdub

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Thanks for you reply. The two "series" fuses would be outside, so need to get IP67 in-line fuses. But, I tend to agree, can't have too many fuses.

A follow-up question.... I think I'll put a 20A circuit breaker at point F. Wouldn't the circuit breaker work about as well as anything for a cutoff switch? Sure should, right?
 

vdub

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I am getting to old and over-thinking things. I used to be pretty quick, but no longer. After working on that diagram for a couple hours and pondering, ie., questioning, how it was coming together, I pulled out Will's book and, low-and-behold, it's almost exactly like what he discusses. With one, notable exception -- these panels must be either old, non-standard, commercial, or all three, since they are 30V. 30V doesn't appear to be standard, however, if my calculations are correct it is an acceptable input for my Tracer 6415AN MPPT.

The input of a 2s2p system will be 60.6V x 16.5A for about 1,000 watts, so well within the specs of the MPPT. I should be quite ok.

And, I checked on the difference between a switch and a circuit breaker. For the most part, but not totally of course, the difference is frequency of use. I think I can get by just fine using a 20A circuit breaker (at point F) and then a 70A circuit breaker going to the battery as on/off switches, since they will be seldom used once the system is turned on.

Battle Born says my batteries should last 15 to 18 years and I expect the same from the MPPT and maybe 10 years on the solar panels. Given my life expectancy of 95 (according to the insurance companies), I will precede the death of my solar system by quite a number of years, at which point it will be my kid's problem. :cool:
 

newbostonconst

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The fuse/circuit breaker protects the wire and is on the up stream side of flow. Your panels being such a long run should have the fuses at the panel. If the run is very short like 10 feet the placement isn't as important. Where current flows in both directions on a long run fuses should be at both ends of the wire. This usually happens with grid tie inverters.

Battleborn batteries have a hard time powering up invertors so be where. I have a 4k inverter and the battery goes into fault mode ever time and has to be reset.

I don't see any grounding.

From what I looked at, nice job.
 

vdub

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I have one Battle Born already hooked up to my invertor, which I've had for about 6 years and I'm charging the battery with a generator. So far, no problem with start ups on the invertor. I wouldn't even know how to reset the BB.

I did put in an iron grounding rod near where all my equipment is in the small building (if you looked at the picture). I put the iron rod in "just because I had it". I know it should be copper. The rod is in about 4 feet. However, I've never hooked it up. I have asked several people about grounding and most have said, "just let the system take care of it". That is, the "system" will act as ground. That doesn't make sense to me. I believe I may have a ground through the panels, because the t-posts are in the ground anywhere from 3 to 5 feet through rock, roots, or anything else that got in the way, they were driven deep. But, you are right, I should put in a real ground with real copper. Thanks!
 

anadiner

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I am getting to old and over-thinking things. I used to be pretty quick, but no longer. After working on that diagram for a couple hours and pondering, ie., questioning, how it was coming together, I pulled out Will's book and, low-and-behold, it's almost exactly like what he discusses. With one, notable exception -- these panels must be either old, non-standard, commercial, or all three, since they are 30V. 30V doesn't appear to be standard, however, if my calculations are correct it is an acceptable input for my Tracer 6415AN MPPT.

The input of a 2s2p system will be 60.6V x 16.5A for about 1,000 watts, so well within the specs of the MPPT. I should be quite ok.

And, I checked on the difference between a switch and a circuit breaker. For the most part, but not totally of course, the difference is frequency of use. I think I can get by just fine using a 20A circuit breaker (at point F) and then a 70A circuit breaker going to the battery as on/off switches, since they will be seldom used once the system is turned on.

Battle Born says my batteries should last 15 to 18 years and I expect the same from the MPPT and maybe 10 years on the solar panels. Given my life expectancy of 95 (according to the insurance companies), I will precede the death of my solar system by quite a number of years, at which point it will be my kid's problem. :cool:
Me too on the getting too old and over-thinking it... hence I went cross-eyed when the diagrams started. How did I end up back in college studying for an exam?

Bottomline, I too have a shed build. I too am rigid about being fire resistant BUT not a fan of fuses cuz seen surges jump em. Yet hey add them but dont rely on them.

Me:
- conduit
- overshoot awg cabling
- use welding blanket pieces as spacers
- ive even put up firebrick...
- multiple ground
- (this works cuz lived it) bottlenecked cabling from OFC to copper aluminum rt before breaker. A big surge came. When it hit the aluminum, snapped the wire but stopped surge dead in tracks. Note: when I say bottleneck, meaning using heavier gauge then the aluminum is required gauge.
 

vdub

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Yes, I over-do it, too. If my calculations say to use 10 gauge, I'll use 8. I guess its an old age thing -- more money than brains. Not a bad position to be in, tho. :)
 

MichaelK

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these panels must be either old, non-standard, commercial, or all three, since they are 30V. 30V doesn't appear to be standard, however, if my calculations are correct it is an acceptable input for my Tracer 6415AN MPPT.
No, these are standard grid-tie panels, and an excellent choice for your new system. They are NOT designed to directly charge a 12V battery, but you are correct that your charge controller will transform the high raw solar voltage down to your battery voltage.

You match the fuse/breaker to the current flowing through the wire. Standard is 1.56X the running amperage. So, 8.27A X 1.56 = 12.9A. Since no-one makes a 12.9A fuse/breaker, buy the 15A version. So, positions C & D should have 15A protection. Position F should be 25A.

A four foot steel rod is an inadequate ground. You need a 8' long copper-clad steel rod. It is not made of solid copper.

What is your system voltage? If 24V, you could bump up the number of panels to six and wire them in a 3S2P configuration. You'll get less voltage drop at 90V instead of 60V. How cold are your winter lows? The open circuit voltage of these panels at freezing will be ~40Voc, but three panels in series would be 120V. Your 150V controller should be able to handle that, but we need the winter low to make an accurate recommendation.
 

vdub

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Good info! Thanks very much. I only found out last winter what the lows were when I had 3 trail cams reporting the temp. Up until then I had no idea because we can't get to the cabin for about 3 months out of the year due to snow. But, actually, don't you mean my high's? They won't be producing any power at all until daylight. But anyway, I was pleasantly surprised to see that the low's stayed at above about 18F and the normal daily high would be right at 25F to 30F. That's why I went with the Battle Born's with the internal heating pad. I also hope that the battery BMS and the solar charger will have enough smarts to protect themselves from serious harm.
 

anadiner

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Yes, I over-do it, too. If my calculations say to use 10 gauge, I'll use 8. I guess its an old age thing -- more money than brains. Not a bad position to be in, tho. :)
I went thru a major fire a few months ago but way before then had experienced crazy surges.

I do spend a lot on wiring but feel its not just safety. A lot has do with cabling is extreme long term. Batteries need replacing and eventually technology will have me upgrading panels, inverters and controller. Like when MPPT showed up.

Also like Im doing a bigger more permanent build right after this one. (Hence buying a reel even tho I dont trust my crimping). Will be re-using cabling.

Makes sense to over-gauge at this point BUT the big downside Ive ran into is the controller ports are too small. Cramming/forcing to fit defeats purpose.

So OMG another thing to research... never ends. (the over-thinking). Found, and now dont recall where, a company that cost more but has managed to narrow low awg.
 

anadiner

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I
Good info! Thanks very much. I only found out last winter what the lows were when I had 3 trail cams reporting the temp. Up until then I had no idea because we can't get to the cabin for about 3 months out of the year due to snow. But, actually, don't you mean my high's? They won't be producing any power at all until daylight. But anyway, I was pleasantly surprised to see that the low's stayed at above about 18F and the normal daily high would be right at 25F to 30F. That's why I went with the Battle Born's with the internal heating pad. I also hope that the battery BMS and the solar charger will have enough smarts to protect themselves from serious harm.
Wondering if that internal heating pad works long-term. (I tend to be cynical... believe it when I see it). Theres prob a post about it.

Anyway, when read ur post, immediately thought about those couple times a year temp gets very low. (I was shocked years back my pipes froze up and burst).

I learned to deal with high temps by simple sensor that auto turns on small fans.
 

MichaelK

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I only found out last winter what the lows were when I had 3 trail cams reporting the temp. Up until then I had no idea because we can't get to the cabin for about 3 months out of the year due to snow. But, actually, don't you mean my high's? They won't be producing any power at all until daylight. But anyway, I was pleasantly surprised to see that the low's stayed at above about 18F and the normal daily high would be right at 25F to 30F.
No, I was not referring to your high temperatures. You MUST design your system to handle the coldest winter lows. The first ray of sunlight on a cold January morning is what could destroy your system. You need to use a string calculator to make sure your wiring design is safe. I like Midnight's.

Plugging in your panel specs, you see a 2 panel string only maxs out at 84V, so that is OK.
1631113249555.png
If instead you wired your panels 4S1P, the resulting voltage would destroy a 150V controller
1631113372270.png
A very doable option for you though is to buy two more panels and wire them in a 3S2P configuration. You'd have less voltage drop at 90V compared to 60, and the 52Amps is within the safe limit of your controller.
1631113449697.png
 

anadiner

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Very interesting. While I d string in parallel, I aim for low current. Is the lower voltage goal u mentioned weather related?

The sun affect on panels after cold temps was interesting. Doesnt apply to me (i barely stop wearing shorts in January - thats not a plus btw - too many warm/sunny days gets annoying) but still, interesting.
 

vdub

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May 31, 2021
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Thanks for all the info. I'm rushing off to get my 3rd booster, so have to wait until later to absorb it all. I'm also getting a ground rod for the system. Thanks!
 

vdub

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I contacted EPEver for some more info on if things looked ok. They responded within just a couple hours. The tech support was fantastic. They recommended several changes which I made. I wish our governments could get along -- the Chinese people seem to be phenomenal and they make really good products. So, anyway, the attached diagram is the final for my system. I bought an entire pallet of the used solar panels that Will had tested and recommended. I only wanted 4 panels, so the remaining 16 were sold -- the price including freight was $71/panel. Thanks to everyone for helping me make sure everything was correct and within the limits of each device.

SolarPanelsDiagram.jpg
 

Atomic Ed

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That is a handy calculator you posted about, I did not know about it before.

I'm also in the stages of finishing my system and trying to make use of that tool but I am confused on the temp coefficients boxes. The values from my newpowa panels seem quite different than the default values shown in the calculator and I would also like to be sure I'm safe at low temps. Maybe one of you pros can help me also understand if I am using the correct values here. Below is my panel values

Temperature coefficient of Voc-(80±10)mV/°C
Temperature coefficient of Isc(0.065±0.015)%/ °C
Temperature coefficient of power-(0.5±0.05)%/ °C
NOCT (Air 20°C; Sun 0.8kW/m² wind 1m/s)47±2°C
Operating temperature-40°C to 85°C
 

acdoctor

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Your SCC has a limit of 750 Watts on 12 volt system. I am over paneling mine but my panels are on flat roof. So I never see more than 75% of watts.
 

vdub

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May 31, 2021
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You're right. I could potentially see 999 watts. I wonder if Epever overlooked that when they gave their blessings. This was their return. I have incorporated all their recommendations.

Solar recheck.jpg
 

vdub

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I have sent another support request to epever. They are really good about getting back quickly.
 
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