Help please- off grid system review

dawgleader1
dawgleader1 Registered Users Posts: 7 ✭✭
Hey all, I'm a newbie to solar and I'm working on my first system.  I'm not located in the Arizona area but I used to live in Nevada for awhile and I'm hoping to see if anyone here can offer any help or advice on my new/ first system here in South Carolina.   I've been doing quite a bit of research and asking for advice wherever I can and I've taken that advice to come up with what I hope is a solid plan. I will still preface this by saying I'm a moron when it comes to this kind of thing and my eyes can go cross when trying to understand electrical and engineering. That being said I've come up with what I think is a workable and safe system.

Backstory: My goal with the system is to have an off grid, emergency back up electrical system. This would be for powering the essentials after a bad storm, a downed tree, or zombie apocalypse. We'd mainly be using it to keep the refrigerator and freezer going and, if we have an abundance of sun coming in, maybe run a microwave or toaster oven here and there. I live in South Carolina and I'm counting on 4ish sun hours a day, less in the winter and more in the summer months of course. I'm trying to make it where my panels are mobile so that we can take them down during 'normal times' and put them up when needed and even move them from spot to spot during the year to collect as much sun as we can. My idea is that the inverter/ battery powerwalls will always be plugged into a home AC outlet to keep the batteries fully charged so if we lose power, we have 20kwh already on hand and then we'd throw the panels up and drop the already prepared cable to collect sun until electricity from the grid is restored.

The system: I have 15x 250w solar panels, 2x 48v 10kwh all-in-one battery powerwalls, and 2x 48v 3000w Growatt all-in-one inverters. I have attached the spec sheets below for review. I will be connecting my panels in 3s5p connection for almost 3800 watts total, the battery powerwalls in parallel to give me 20kwh of power storage, and the inverters in parallel to give me a total of 6k watts from my inverters. The best places on my property with the best sun exposure for the panel set up will be between 100-150' from the inverters & battery powerwalls so I'm trying to utilize proper gauge wire to limit loss and guarantee safety. I'm planning on using 6 AWG wiring for my solar panel array since it's rated for up to 55a; I'll be using 4 awg for my inverter and battery powerwall connections. I am planning on inserting a breaker between the solar panel array and the parallel connected inverters as a safety precaution. In an attempt to make it easy and clear, I've attached a couple sketches below to show my plans. All comments, advice, suggestions, and warnings are greatly appreciated but I have a few specific questions:

1) Is the attached (picture below) breaker ok for this purpose? if not, what's wrong with it so I can look for a better option? Or do I even need a breaker since my Growatts have built-in protection? I felt redundancy in this case was a good idea since I don't want to burn my house down or damage my system.
2) Do I need to add any additional breaker or fuses between the battery powerwalls and inverter? many of the schematics I've looked at have them but with my powerwalls I believe they have all the necessary protection built-in, but I may be wrong. If I need to add a fuse or breaker here please advise on what I would need.
3) Am I good on the 6 awg wire for my panel array? From the calculators and charts I've looked at, if I'm understanding them correctly, I would be running 4-5.5% loss, which I think I'm ok with unless there is a safety issue I'm not aware of yet. From what I understand, going with 4 awg would result in a 2.5-3.5% loss, so not a HUGE difference in the grand scheme of things, at least I don't think. I've found some 6 awg wiring that I'm probably going with and have attached the picture below, is this good or should I look at something different. I wasn't able to find any reasonable price on 4 awg, at least not yet, but if that's what I need to go with I'll do some more digging.
4) with the wiring above, since I want to be able to move my panels from spot to spot on the property and this isn't a year round, out in the weather system, is is ok just to run the cable across the ground? Or do I need to run it through a PVC conduit pipe or even underground?
5) Do I need to incorporate a bare copper ground wire? I don't think I need it but I have seen some people talking about it so just wanted to check. If so where along the line would I connect that?

Well that about wraps it up. I've attached as much info that I can think would be relevant but if you need to know something else to make suggestions pleas just ask. Thank you very, very much! I greatly appreciate any and all help offered.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Welcome to the forum DL1,

    Before I (we) go into the details about your system design (needs more breakers/fuses at least)--I would like to nail down your loads and expected system usage... You have 6 kWatts * 2 for 12 kWatts of inverters and 20 kWH of storage--Near "full power" (10 kWatts) that would drain your battery bank in 2 hours. With designing your system based on your loads/needs--Generally the loads you have done conservation (energy star refrigerator/freezer, LED lights, using natural gas/propane/wood/etc. for heating, and such... Just to give you some ideas:
    • 1,000 Watt*Hour per day (30 kWH per month) system (lights, RV water pump, laptop, cell phone charger, and other small loads)
    • 3,300 WH per day (100 kWH per month) system--Add well pump, washing machine, TV, Refrigerator, more lights and computer usage.
    • 10,000 WH per day (300 kWH per month) system--A very energy efficient home with natural gas/propane for heating/cooking/drying clothes, extra freezer, etc.
    • 30,000 WH per day (900 kWH per month) system--Most north American homes are around 300-1,000 kWH per month (all electric home, A/C in Texas, etc. --More energy--Texas can be approaching 3,000 kWH per month).
    I have two suggestions for "backup power":

    First--A generator... 20 kWH of electricity is around (~4 kWH per gallon) 5 gallons of gasoline. Store 10-20 gallons of gasoline (with preservative), a smaller genset (like a Honda eu2200i) to run a couple fridge/freezers, some lights, radio, etc... And perhaps a second genset in the 3.5+ kWatt range both for backup (things fail), and to use when more power is needed (shop tools, portable saws, large well pump--pump to cistern).... 10 gallons of gas will run an eu2200i (or perhaps an eu3000is) for 5 days. Just recycle the gasoline into your vehicles once a year. Heck of a lot less money up front vs a large solar power system + Li Ion battery bank... And virtually no maintenance (I have pickled a couple Honda eu2000i gensets for 5-12+ years--And they both started on the third pull with the stored gasoline).

    For a purely backup system... Genset is hard to beat cost wise... If you have natural gas or propane tanks on property--There is your fuel "storage".

    Second--Solar Power--Suggest that you aim at a 3,300 WH per day system. That will run one refrigerator (and probably a second freezer during the sunny parts of the year) and give you lights, small water pump (if needed), possibly run a washer a couple times a week (during sunny weather). That would be something like a 1,200-1,500 Watt AC inverter and a ~650 AH @ 24 volt battery bank (using Flooded cell lead acid "golf cart" batteries or better). Keep a small genset+AC charger for winter/stormy weather.

    Big solar power systems are expensive--And cost money to maintain (primarily the battery banks). Just sitting for backup power, or actively cycling--The battery costs--New batteries every 5-10+ years (guess), The inverters/charge controller/etc. -- replace every ~10+ years.

    The quick 3.3kWH per day system calcs:
    • 3,300 WH per day * 1/0.85 AC inverter eff * 2 days storage * 0.50 max planned discharge (for FLA bank) * 1/24 volts = 647 AH @ 24 volts
    Rates of charge run from 5% to 10%-13% typical... 5% for emergency/backup systems/sunny weather usage... 10%-13% for full time off grid typical:
    • 647 AH * 29 volt battery bank charging * 1/0.77 panel+Controller deratings * 0.05 rate of charge = 1,218 Watt array minimum
    • 647 AH * 29 volt battery bank charging * 1/0.77 panel+Controller deratings * 0.10 rate of charge = 2,437 Watt array nominal
    • 647 AH * 29 volt battery bank charging * 1/0.77 panel+Controller deratings * 0.13 rate of charge = 3.168 Watt array "typical" cost effective maximum
    And sizing the array based on your location, hours of sun per day, and how much genset runtime you will accept. South Facing, fixed array, Columbia SC:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Columbia
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 56° angle from vertical:
    (For best year-round performance)

    JanFebMarAprMayJun
    3.67
     
    4.03
     
    4.89
     
    5.47
     
    5.40
     
    5.23
     
    JulAugSepOctNovDec
    5.18
     
    4.95
     
    4.81
     
    4.80
     
    4.05
     
    3.67
     

    Lets guess 3,300 WH per day, and 4.0 hours of sun (not a bad guess for non-winter, and you still have a fair amount of winter sun):
    • 3,300 WH per day * 1/0.52 off grid AC system eff * 1/4.0 hours "break even month" = 1,587 Watt array "break even"
    I use "break even" to indicate this is an average (more or less) best case harvest for November/February. In off grid systems, you generally design a larger solar array so you have "enough power" during bad weather, and reduce (or possibly eliminate) genset runtime... So, for example say you have a refrigerator and evening LED lighting at 2,000 WH per day usage... The rest of the appliances are either turned off during bad weather or run the genset... So a base load system should use around 50% to 65% of the "predicted system harvest":
    • 2,000 WH base loads * 1/0.65 fudge factor = 3,077 WH solar harvest for 2,000 WH per day base loads
    • 2,000 WH base loads * 1/0.50 fudge factor = 4,000 WH solar harvest for 2,000 WH per day base loads
    Solar panels are just "single weight" glass panes with an aluminum frame. Normally, they are mounted to pretty substantial racks to take wind storms and hail. Just staking panels on a grass lawn--A light wind can knock them over an break them (they are tempered glass--even a good scratch can shatter the safety glass).

    These days, Racking is roughly the same price ($ per Watt) as the panels (excluding labor).

    Those are my suggestions--Your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Stop buying stuff!

    At first glance, you need a combiner box at your solar array. It will combine each string of 3 solar panels with a fuse or breaker with the other strings.

    Your described "Powerwall" isn't. a Powerwall is a Tesla 'thing' that includes an inverter/charger.

    Your chosen breaker is only AC rated, it should not be used with DC circuits.

    Doing something portable with a 3750 watt array, would be a pain. Even if you could make perhaps 2 trailers and have locations with pre-established anchor points. It really sounds over whelming.
    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.
  • dawgleader1
    dawgleader1 Registered Users Posts: 7 ✭✭
    Hey BB, thank you very much for your input, the help is much needed and greatly appreciated.  

    First point, is I already have the listed components above.  I already have the 2x Growatt inverters, the 2x battery packs, and the 15 solar panels.  So unfortunately if I purchased not the ideal component, I need to try to use what I have unless it's unsafe or completely stupid to do so for some reason.  The only thing I'm missing is the wiring, fuses, and breakers.  I'd like to order that now so that's why I'm posting on here to get some input.  I've learned a lot during my research and getting advice from people but, figuring up watts, amps, voltage, and understanding all of this kind of thing give me a headache and my eyes get blurry.  So, I'm looking for help from some experts like you to tweak my plan so that I order the right wiring and don't burn my house down.  

    Secondly, to clarify, my inverters are 48v/ 3000w each so that would put me at a total of 6000w on the two vs the 12kw you mentioned in your first paragraph.  A small thing since the rest of your point remains valid, but I wanted to point that out.  As far as draining my battery pack quickly, in 3-4 hours if you take the combined 6kw on my 20kw batteries at max, if there is nothing connected to the batteries drawing or it's a minimum load like a refrigerator and freezer at  around 4kwh/day on the bare necessities, then it won't be pulling the full 6kw, it would only pull the needed energy so my battery power would last, I hope, a few days, even without any sun.  Unless I'm missing something here, as I said I'm brand new to this kinda thing.  

    Third, I agree a generator is a great go to.  I have already invested in a 4500w gasoline, sinewave generator.  I live out in the boonies and not close to any natural gas like in the city and I wasn't really keen on getting a big propane tank mounted in the yard just to hold propane for an emergency even though I did look into it and considered it.  I felt the best investment for the long term was a mid-sized solar system that I could move and change as needed.  So that's when I started my research and tried to come up with something I could build myself.  While I'm willing to invest in this I didn't want to go overboard and invest $20K+.  I did quite a bit of research and investigated a bunch of battery options.  That's were I came up with my 'powerwall' battery packs which I though would give me enough, 20kw, power to not only run our necessities but also get us through a couple days of no sun if the power loss is due to bad weather.  So with my system at a combined 6kw on the inverters, 20kw on the combined batteries, and me pulling in around 3700w per hour on my panels, if I get 2-3 hours of sun on average days and up to 5 hours on a good day then I felt this would supply us for quite a while on the bare needs and even allow us to splurge on really sunny days.  With keeping the batteries connected to the grid with an ac plug, that keeps the batteries full so we have 20kwh of power from minute one of a power loss.  If it's something short term like a couple to a few hours or so, which is almost always the case, then we don't have to lug out the generators or the solar panels, we have enough power on hand to last us easily.  If it's something more major and the outage runs into a day or longer we can put the panels out and cut back to the bare needs to hold us through where we could last a few days without any power or sun if we had to but if we can get sun we can last much longer.  At least this is my overall idea of how this all pans out in my cloudy mind.  

    Lastly, your point on my idea of the panels being mobile, that was a pie in the sky idea.  I realize that each of my panels weigh 40lbs plus the mounting, wiring, etc.  I'm not naïve enough to just stake them in the ground, even though I am pretty stupid sometimes, lol.  I do plan on making a racking system, probably a wooden one that can be mounted in different parts of the yard depending to the time of year and sun.  I wouldn't be moving the panels hour to hour or even day to day, but maybe from week to week or more realistic month to month as in the Winter we get a different and lower sun pattern than during the other seasons.  Again, just an ideal situation in a perfect world, maybe not realistic or doable.  Right now I'm trying to get my solar plan down so I can order the last parts of the system such as my fuses, breakers, and wiring.  I'll be working on the racking system later, it will probably be on a wood structure so I can take it down when normal times abound.  

    I hope this clarifies some of my thought process and ties it into your input.  Please remember I'm new and never done this before so I'm sure some of my ideas and plans are off base.  I'm just hoping for as much great advice I can get so it can be the best possible and safest system for my family even if it's not perfect or and ideal setup.  Thanks so much for helping out.  Anything you can clarify or add would be very welcome.  
  • dawgleader1
    dawgleader1 Registered Users Posts: 7 ✭✭
    Hey Photowhit, thank you for jumping in and helping me out.  

    As you've suggested I've slowed down in my purchasing and tried to do more research.  I jumped the gun on a couple things but I got worried and pulled the trigger.  I started doing research and initial plans on this in the middle of 2019 but was pretty laissez faire about it and being new needed to do a lot of research before I was comfortable.  I talked to some people, did some reading, and discussed ideas with some battery and inverter suppliers but I kept getting mixed information from one source to another and it just confused me more.  Then we rolled into early 2020 and all crap let loose and we had Covid, China trade issues, lockdowns, economic problems, trucking issues, and other problems popping up.  So I jumped and ordered the stuff that I was pretty sure I wanted anyway because I was worried about things getting really bad and not being able to get what I wanted any more.  So I ordered my inverters, my batteries, and my solar panels figuring I'd put it all together a little later with things I could get more locally and USA based.  So that's why I have what I have.  Knowing what I do now I'd probably have still gotten the same battery packs and solar panels but would have gotten a different inverter set up.  But oh well, it is what it is.  So now I'm trying to do my due diligence on proper lay out of my plans and ordering for my wiring, fuses, and stuff to put it all together and make the best system I can with what I have and not got bankrupt doing it.

    I understand that my use of 'powerwall' is myself loosely using the term, I know 'powerwall' is a trademark of Tesla but I like the way it sounds and it does communicate that I don't have just a bunch of battery cells or Battleborn batteries laying around.  My batteries are, hopefully, fully integrated with solid, quality bms and safety features.  I did a lot of research before I bought my GSL battery banks/ 'powerwalls' and think/ hope I got a good product.  I can provide any specs if you'd like or think that would be helpful.  

    As far as my choice for the breaker:  To be honest with you, that being an AC breaker didn't register. I was originally going to go with the breaker attached below but it's only rated to 72volts and with my 3s5p I'll be at 90.9VMP, so I didn't think it would work or be safe so I went with the other one that I saw was rated at 400v, it didn't click that it was ac vs dc. So, thanks for pointing that out, I'll have to dig into some other options, unless you have a suggestion. As far as the fuses for the strings I didn't know if I needed them or not since It was being wired into an all-in-one inverter that has protection but I did consider it and looked at the fuse below for that purpose. It's a 15a and I'll be at 8.27a per 3 panel string so I think that would suffice, or I could go with a 10a of the same if 15a is overrated. I had also found the mini breakers below but they are only rated to 24v and start at 20a which I thought was under rating on the voltage for my system and over on the amps. I'll definitely look into some other breaker/ fuse options. 

    And then, as you point out, the 'mobile' idea part of my panel array is a pie in the sky thing.  Please see above, I went over my vision in my response to BB. 

    Thanks for helping out, any other points or advice you can offer would be fantastic.  I hope to get as much feedback as you have the time and patience to provide.  Thank you!
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    I wouldn't buck the system, with 3 panels in series the only option of the 3 that is likely to match your curcuit would be the inline fuse with the appropriate fuse if one is available.

    Better to run the series of panels into a combiner box. Since you will be using the inverter chargers to charge the battery bank, You would be running 3 strings to one and 2 strings to the other. The one serviced by 2 strings, wouldn't need breakers or fuses each string as 1 string couldn't over power the other, so none needed. The inverter/charger serviced by 3 would need a combiner box for the 3 strings. Something like this would work in a weather tight enclosure;
    Midnite Solar Baby Box Enclosure for 1-4 Din Rail Breakers

    https://www.solar-electric.com/baby-box.html

    ...and use Midnite DC breakers;
    Midnite Solar MNEPV 150 Volts 15 Amps DC Circuit Breaker
    https://www.solar-electric.com/midnite-solar-mnepv-15-amps-circuit-breaker.html

    Use a UL Power block or some other combiner to connect the output. You could even use Y connectors to combine the negative lines if you can use 10 gauge to run to the inverter charger.

    I assume the battery banks are lithium, Please be aware that lithium can NOT be charge when they are below freezing and may be 'wonky' below 40 degrees. So need to make precautions!

    Lithium doesn't really need to be maintained at or near full, but you don't want them to go below 10-20% or it shortens there life (or above 90% long term) But you should be aware of your state of charge and able to maintain it in between.

    A trimetric or other type of shunt based battery monitor might be advised.
    Bogart Engineering Trimetric TM-2030-RV Battery Monitor

    https://www.solar-electric.com/bogart-engineering-tm-2030-rv-battery-monitor.html

    Need to figure out how well the inverter chargers work together. I don't know how well the inverter chargers work with each other, do they sync up their sine waves? ...or sync up/ communicate with each other when charging, also don't know about any restrictions in using your battery banks in parallel. Do not take any chances with lithium battery banks!!! They can rapidly dump their stored energy. Think instant welding!
    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.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    I would strongly suggest getting breakers.  You will have several identical strings, and being able to shut down some, and measure against it's brethren ( and cistern) is invaluable for ease of troubleshooting.  i use the charge controller's internal metering as a measure as good as any.
    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 ,

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    So you intend for the Grid to be your backup generator.  Any plans for cloudy weather & the Grid being down ?
     I've got over a week coming up, of really poor generation -   (kudos for Weather Underground - www.wunderground.com )
    for having % cloud cover in their forecasts.




    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: 33,431 admin
    DL1,

    Sorry... Yea I got the 6 kW total vs 2* 3 kW inverters... I thought I had corrected my math--But obviously, I did not.

    I highly suggest that you will not move the array during the 4 seasons... People either go with 1 or 2 axis tracking systems, or put some panels facing south east and other south west to get "more hours of sun" per day (virtual trackers)--Great for Lead Acid batteries which need "more time on charge" to get a full charge...

    Or they have an adjustable tilt array... Lay more flat for summer, and more vertical for winter (or near vertical to better shed snow).

    I wonder how many people actually adjust tilt a few times a year--Vs just leave the array fixed (or possibly even buy more panels--That are at a historically low $$$/Watt pricing these days--Just buy and install more fixed panels for more harvest).

    Lithium batteries (LiFePO4 or similar) are pretty near "perfect" batteries for off grid/RV usage... But they do have their own issues... Easy(ier) to damage from over/under voltage. Can be damaged by too high charging or discharging current, etc.

    The "best" solution seems to be the integrated Battery Monitor System that talks with the AC/Inverter-Charger/MPPT solar charge controller... If you do not have this communications, you need to be more careful when running your system to help make sure you do not "stress" the batteries. "You" need to design and operate the system with battery limitations in mind (perhaps do not run the genset/AC charging during daylight hours when your solar array is also providing charging current, etc...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dawgleader1
    dawgleader1 Registered Users Posts: 7 ✭✭
    edited December 2020 #10
    Hey Photowhit,

    I've looked into the breaker/ fuse thing a little more and came up with a couple revisions on my sketches to maybe better protect all of the components.  Please check out the below and let me know what you think.  In this drawing I'm using 15a fuses connected to each of the positive connections off of each 3 panel string, so 5 fuses.  I'm also considering using 15a breakers, as Mike suggested, instead of the below pictured fuses.  Please let me know which you think would be best.  These would feed into the inverters and I'd use one of your suggested Midnite breakers there, 150vdc 70a.  I've changed my inverter and battery connection as someone else suggested so the batteries have better symmetry and between the inverters and batteries I'm using a 100a Midnight breaker.  Hopefully these changes are an improvement and I'm not moving backwards. 

    One last point is you mention lithium batteries.  Yes, my battery packs/ 'powerwalls' are Lithium ion batteries with fully integrated BMSs.  You mention they can't be charged below freezing, I was aware per the battery specs that the lower charge temp was 0c/32F but I didn't know about them being 'wonky' below 40F.  I'll be mounting my batteries and inverters in my garage, it's fully enclosed but is not insulated.  Here in SC we don't run into extreme cold temps but we will run below 32F on occasion during the winter as we're rolling into and we have quite a number of nights we'll run below 40F.  Do you have any ideas on any precautions as you put it?  I wouldn't guess a heater would be a good idea near batteries so anything you could offer would be appreciated.   

    Please offer your opinion on all the above, I apologize for sounding stupid and needing everything drummed down.  Thanks.
  • dawgleader1
    dawgleader1 Registered Users Posts: 7 ✭✭
    hey BB, thanks for coming back.  Trust me, I get all this scrambled like eggs, that's why I'm here looking for help.  lol.

    I'm reconsidering the "mobile" part of my panel idea.  I've gotten quite a bit of 'non-positive' feedback on that.  Thinking about it more I can easily see it would be a mammoth of a project and would also increase the likelihood of causing damage to the system or injury to myself.  So that's shelved, I've started looking into some options as you suggest like the tilting idea instead.  I'll get back to you on that once I have a chance to delve into it more.  

    My Batteries are all in one battery packs/ powerwalls from GSL with integrated a BMS in each one and is completely compatible with my Growatt all-in-one inverters.  I was told, and from what I read in the specs, that the batteries have a full BMS with overcharge and overheating protection.  I hope I understood everything and got what I paid for and the batteries are safe and good quality.  
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    I haven't read your inverter/charger manual, but generally you want an array attached to only one charger. As I said I'm not familiar with the compatibility of your inverter/chargers. It does appear you can parallel up to 6 units (from the specs) I suspect there is some cabling involved, Check the manual for info. 

    I like the panel mount breakers between the battery banks and inverter. Those breakers are designed to 'face mount' so likely you will want a box for them. Also need to check on paralleling the battery banks both with battery manufacturer and BMS manufacturer. Lithium battery banks are not 'my end of the pool' at least not yet... 

    I may read up later tonight...
    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.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Don't forget, you need to order Fuse Holders too, so you have someplace to put the fuses..
    I generally think the inline holders are junk, you have to crawl around and open them up (at night, or with array DISCONNECTED) to check the fuse.
    The holders & fuses (good ones, not the inline junk) will cost nearly as much, or more, as a proper breaker. And it works like a switch
    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: 33,431 admin
    Just to clarify Mike's comment about fuse holders vs breakers...

    There are "touch safe" fuse holders--But if you pop one open under load, they can arc and catch fire... So you cannot use them as "switches" when there is significant current flow.

    http://www.midnitesolar.com/pdfs/MNPV2_4_Pre-wire.pdf (page 4 photo and warning)

    Breakers do both the current trip, and can be switched under load too (there are many types of breakers out there--So read the specifications closely).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dawgleader1
    dawgleader1 Registered Users Posts: 7 ✭✭
    Hey Guys,

    I've been doing some more research on the fuse vs breakers.  I also like the extra flexibility of a breaker vs a fuse however with my panels being mounted so far away from my inverters and battery packs, around 100-150ft, I would have to mount a panel box to the end of my panel racking system to run each of my strings to, and then run my 4 or 6 awg wiring from there to my inverters in the garage. It seems that would raise my costs quite a bit and it seems so much simpler to just utilize the inline fuses.  Please correct me if I'm making the breaker idea more difficult than it really is.  So, taking that into account, I'm leaning toward running my 3 series strings in parallel using the Rich Solar (or Renogy) 15a inline fuses below connected together with a 2-to-1 y branch connector which is rated at 50a and then run them all into the Midnite breaker before my inverters.  I will use the 5' or 10' 10 awg extension cables between the strings as needed to connect them since the cables on the panels won't be long enough to reach all the way across all 5 strings.  Then into the last y connection I'll lock in my 6 awg wiring to run from the panel array to my inverters in the garage.  How does that look???
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    I've been doing some more research on the fuse vs breakers.  I also like the extra flexibility of a breaker vs a fuse however with my panels being mounted so far away from my inverters and battery packs, around 100-150ft, I would have to mount a panel box to the end of my panel racking system to run each of my strings to, and then run my 4 or 6 awg wiring from there to my inverters in the garage.
    That is common and called a "combiner box". When things are a large distance apart, it's very common to have both a combiner box and a breaker ahead of the charge controller. I think it meets code without, so long as there is a fuse or breaker on each string.

    Here's my combiner box, which is a fuse box. It actually handles 2 arrays going to 2 charge controllers.


    Most larger system like the one you are building, will have a breaker box. I use a Midnite E-Panel.

    These are diagrams of the current flow in my Epanel, in 2 pictures. The solar arrays come in from the back at the top. Red arrows are the positive and the blue are the negative.


    ...and the flow from the Charge controllers back through the panel.


    Perhaps as clear as mud, and very crowded, More so after this when I added a breaker for another inverter, and I sould max it out pretty much if I ever get around to installing a 3rd charge controller.

    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.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    edited January 2021 #17
    Cost of wiring... More or less, the cost of 4x 10 AWG copper is "the same" as 2x 7 AWG cable (for every 3 AWG change in gauge, there is a 1/2x or 2x change in cross section sq inches). So the cost of a single heavy cable vs the cost of 2x lighter cable is about the same (there is not much "odd AWG" cable available--So there is an added cost to go from 4x 10 AWG to 2x 6 AWG (more than 2x more copper in 6 AWG cable vs the 10 AWG).

    For solar panels, the fuses/breaker are not really there to protect the main line wiring (like the standard use for fuses/breakers). In this case, you have multiple power sources (multiple parallel connected strings of panels).

    Generally, if you look at the panel specs, you will find (for example) a Isc 10 amp rated panel will require a 15 amp series protection fuse.

    The panels probably have at least 12 AWG wiring, which is good for ~20 amps max... So a 10 Amp Isc and 15 amp fuse is well under the rating with 12 AWG cable.

    The issue is when you (typically) have 3 or more strings in parallel of solar panels...

    I.e., if you have one string, no series fuse required. The panel will output 10 amps max, and take 15 amp fuse--So fuse/breaker would never trip.

    If you have two strings in parallel, and short one string (or panel), then the only current source is the second "good string"--Again, 10 amps Isc into a 15 amp rated panel+wiring system... No problem, no series fuses required.

    If you have three strings in parallel, One shorted string is fed by 2x Isc of the "good strings". Then you are looking at 20 amps into a 15 amp max panel+wiring string. Put a 15 amp fuse/breaker on every series connected string (3x strings, 3x fuses/breakers, one in each string).

    Now, you can choose to bring 3x pairs of cables (one pair from each string) back to your battery shed. Put "combiner box" on wall of shed. Bring 2x heavy cables from combiner to charge controller.

    Or, you can put the combiner box at the array, and just bring the heavy cable from the remote combiner box to the charge controller--You may want to put another (larger ~45 amp breaker) next to the charge controller so you can have a nice on/off switch (breakers make good on/off switches--Fuse and fuse holders are not usually rated for switching/opening under load).

    The reason for using 3 breakers at the array (or one per string)--It is very easy to switch off one string at a time to make sure that all three strings are properly sharing current (each 1/3rd of the total array current). If you switch off one breaker and have zero or very low current drop--Then that panel/string/its wiring connections probably has issues.

    You can (more or less) skip the three breaker handy debug process, and get a $50-$150-+++ AC+DC current clamp DMM (digital multimeter). These are very quick, easy, and accurate (if you DC zero them first) to use--Just clip one wire from each string and read the current--All strings "match" current, or one or more low low current--You know where to look.

    https://www.amazon.com/UNI-T-UT210E-Capacitance-Multimeter-Resolution/dp/B075ZHDQFP (cheap, "good enough" for up to 100 Amps)
    https://www.amazon.com/gp/product/B019CY4FB4 (medium price meter to 400 Amps)

    Good quality in-line fuse holders can work. But they need to be water tight and sun/UV resistant. We have had folks with "automotive" style fuses and fuse holders--And even running at less than 1/2 rated current, poor connections at the terminals overheated them and just about started a fire.

    Solar and battery systems can run at "Rated Current" for 5+ hours at a time... Even the standard NEC house wiring stuff is not rated for that... There is an 80% (or 1.25x) derating factor for continuous loads (like gym lighting--Constant known load--Need heavier wiring to avoid overheating in long term operation).

    Placing fuse holders/fuses/breakers in a metal box (especially in a wet/fire hazard location--Such as over a field of dry grass) is not a bad solution long term. Protect your components from damage, reduce the risk of fire, and everything "just works"--You are not going out there every spring trying to debug wiring issues.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dawgleader1
    dawgleader1 Registered Users Posts: 7 ✭✭
    Hey Photo and BB.  I just wanted to wish ya'll a great new year.  I hope you and your family had a good and safe Christmas and New Year.  I've been super busy with a bunch of stuff but I'm still working on this.  I appreciate the new information you gave me and as soon as I get a new plan worked up I'll get back with you guys if you're still willing to look things over.  I'm also playing with the idea of trying to get a consultant to look over my final plans before I 'go live'.  I don't know how much that would cost or even where to find someone but if either of you have any ideas of where I could find a KNOWLEGEABLE and RELIABLE professional that would look over my stuff and talk to me about it that may be helpful to me to wrap it all together.  I have learned SOOO much from you guys and doing some additional research and I think I understand it and have a pretty good plan now, I'm still new to this and get very easily confused by all this electrical stuff.  Thanks again!!