I inherited a solar energy system that does not work....

zachandme
zachandme Registered Users Posts: 3 ✭
edited June 2016 in Solar Beginners Corner #1
...and I would like to get it to work! :)   Thank you very much for any assistance you can provide.

I have all the specifications of what is in the system and the parts were all purchased within the last year or so.  Some things are hooked up, other not.  All I can say is if it weren't for YouTube and this forum, I'd be completely lost.  My first question is whether I have the top half of the basic layout correct.

12 panels in total, but they are split so that 6 currently feed into 1 plastic junction box, and 6 feed into a second junction box.  The cables came with the panels.
The junction boxes don't do anything but provide a way of bundling the 6 cables.
Wires come out of each junction box and each connects to a battery charger.
Each battery charger connects to two 12v batteries (for a total of 4 12V batteries)
The two batteries are connected together, parallel, but are currently not connected to each other.

It looks like there are cables to connect each pair of batteries to 2 spots marked for mounting "DC Dis"
I assume the plan from there is to connect the DC Disconnects to the Inverter, and the inverter to breaker box.

Specific questions:
  1. Does the layout look reasonable for what I want to do?
  2. Do I need solar junction boxes instead of regular junction boxes?  They look like they typically are for four panels each.  
  3. Is a split system like this with two battery chargers, and two pairs of parallel connected batteries, and two DC Disconnect switches the most efficient?  It seems to me I would be better with one battery charge controller and four batteries connected parallel.

System Description
It's for a studio / workarea (off grid) that needs to power at least one, if not two, computers.  The interior space is roughly 10' x 10'.  There is some LED lights in there now, and I am thinking about putting in some photography processing equipment.  If it doesn't work out as a studio, I have an alternate use in mind that would suit me just fine.

What I have:
12 Ganz GSP-55 PV's (already mounted flat, in series)
2 Plastic junction boxes (already mounted, but completely empty) Home Depot variety with punch outs.
2 Ganz GCC-D10A Dual Battery Charge controllers
4 C&D UPS12-490MR 12V Batteries (brand new!)
1 500 Watt Inverter (Royal Power)
1 Breaker box with 3 30 amp GFI breakers

I have 1/0 and 2/0 cable on my shopping list, along with connectors.  Also two DC Disconnect switches?


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Comments

  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    edited June 2016 #2
    Welcome to the forum,
    I don't know where to begin... everything is wrong, the panels, the controller, the batteries, the junction boxes, everything.

    IMO, you should design a system on paper that will meet your needs, and then figure out which parts of your system can be used.

    Those batteries are not a good choice for an off grid cycling application.  They are designed to live for years in float and then be called into action when the grid goes down.  They have a 20 hr capacity of 139 ah.  Four of them have a capacity of 556 ah at 12 volts = 6.7 kwh.   It would be a good idea to have enough panels to provide a 10% charge rate, which would be 56 amps.  Your panels have a max power current of 3.2 amps, and 12 of them combined are probably a bit anemic for that battery bank. 

    The panels, if used in parallel with a 12 volt battery bank, need to be combined in a proper combiner box with a circuit breaker for each panel. This is for safety.  If one of the panels faults, the combined current from the other panels could backfeed the faulted panel and cause a fire.

    I don't know much more about those particular panels other than they are incredibly expensive per watt.

    I notice that the controller can work at 24 volts.  That would be a good thing for you because you would have fewer parallel batteries (always a good thing) and you could put the panels in 6 strings of 2 panels per string.  That reduces the amount of combining, and the number of circuit breakers.

    I doubt the inverter would work at 24 volts.  If you are willing to replace the controller with an MPPT controller, you have more configuration options for the panels, and will see a gain in your energy harvest under most conditions.

    But really, the first step is to figure out what are your energy needs, and then figure out what use to get there.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3

    I'm not so sure the batteries are a poor choice, While they talk about standby for 10 years they also say 300 cycles to 100% discharge, I'd expect 4x that to 50% discharge. I've never used AGM's though and high rate discharge would seem to be lead calcium. I've never seen "watts per cell" and never heard of a discharge rate of 15 minutes...

    I would say, with what you have, I'd aim to setup as a 24 volt system. The 2 - 10 amp charge controllers can be used to charge a single battery bank of 4 batteries and should work (actually only work) with 6 of your 55 watt panels. It might have been the original designed plan to have a 24 volt system.

    Check the inverter you have to see what voltage it is designed to accept.


    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.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #4

    BTW - What "photo processing" do you plan, not much done with photography that's not done on computers anymore!

    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.
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  • zachandme
    zachandme Registered Users Posts: 3 ✭
    #5
    Thank you so much for your feedback.  Yes, I am designing a system on paper.... or trying to.... but someone with a lot more knowledge than I had put these parts together and I don't have his plans!  I will decipher what you sent me as best as I can, and then take it from there.  I agree that I need to put a list together of what kind of load I'm going to need.  I read that with computers, I need to have a pure sine inverter. Agreed?

    Should I be hooking the panels up in series to gain the extra current/watts? Or does that depend on the load I require?

    I appreciate your assistance.  I am really enjoying the learning process but want to do this without blowing anything up. 
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
    zachandme said:
     I read that with computers, I need to have a pure sine inverter. Agreed?
    Maybe.  The answer is also maybe for motors, and practically everything else.  It s difficult to predict what will work, what will work poorly, and what will be damaged.  Get a pure sine inverter.
    zachandme said:
    Should I be hooking the panels up in series to gain the extra current/watts? Or does that depend on the load I require?
    The answer depends on the battery voltage and the controller.  If you stick to a 12 volt system and your ganz controller, all the panels must be in parallel.  But not all of them... some of them can't be used at all... as Photowhit mentioned (and I should have mentioned in my earlier post) your panels exceed the capacity of the controller (if you operate at 12 volts).
    zachandme said:
    someone with a lot more knowledge than I had put these parts together and I don't have his plans
    I agree that you don't have his plans.   Tell us more about the inverter... it might give a clue as to whether the plans were for a 24 volt system.

    By the way, where is the cabin located?  Those panels are meant for a marine environment and are very expensive per watt... are you in a corrosive environment?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #7
    I guess that Zachandme is posting from around Bloomfield NJ... (cabin is elsewhere?). Just to give an idea of solar radiation for the area:
    http://solarelectricityhandbook.com/solar-irradiance.html

    Bloomfield
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 49° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.22
              		3.88
              		4.44
              		4.68
              		4.83
              		4.98
     
    Jul Aug Sep Oct Nov Dec
    4.99
              		4.87
              		4.73
              		4.30
              		3.29
              		2.93
     
    Zachandme, take your time... Go through the process with us step by step. It will all start to make sense as we go through the process.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • zachandme
    zachandme Registered Users Posts: 3 ✭
    edited June 2016 #8
    Bill - you are pretty close.  The workshop is in pennsylvania in an open area without trees just about the same latitude of Bloomfield NJ.  Going with what Photowhit suggested, I only need 6 55W panels hooked in parallel for a 24v system? That will work with one of my existing battery chargers, provided I use one Ganz GCC-D10A Dual Battery Charge controller.  This may seem pretty basic, but does the voltage on the solar panels or on the batteries determine whether it is a 12v or a 24v system.  I was thinking I had a 48V system because I had 4 batteries each at 12 volt.

    Vtmaps said:  "The panels, if used in parallel with a 12 volt battery bank, need to be combined in a proper combiner box with a circuit breaker for each panel. This is for safety.  If one of the panels faults, the combined current from the other panels could backfeed the faulted panel and cause a fire."

    That's a good heads up to have.  If they are hooked up in series, does the same apply?

    The inverter listed is a Royal Power PI5000 - 12 Power Inverter 5000 Watt 12 Volt DC to 110 Volt AC  (I guess that is what makes it a 12v system?)

    Update:  Just looked up MPPT.  That seems like a no brainer and I should definitely do that!


    - B

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #9
    If you have a PWM controller (also minimum working voltage for MPPT)... Vmp-array~18 volts for a "12 volt battery bank". And Vmp-array~35-36 volts or so for a 24 volt battery bank.
    he
    If you have 6x 12 volt panels, you would put two panels in series, then 3x parallel strings to charge a 24 volt battery bank.

    If you get an MPPT controller, you can run from Vmp-array minimum (18 or 26 volts) to the Vpanel max input voltage for the MPPT controller (depends on brand and model--nominally 40 to 100 vdc for the more common MPPT controllers).

    The "big" reason to get MPPT is because you have a longer distance from the solar array to the battery shed+charge controller. You can run "high" Vmp-array and the MPPT controller will efficiently down convert (~95% efficiency) to the low voltage needed by the battery bank.

    More or less, if the array is on top/next to the battery shed, a PWM controller can work fine. If the distance is multiple 10's of feet to 100+ feet away, you really need an MPPT controller (plus "higher voltage" array) to have a cost effective system.

    Also, if your system is less than ~400 Watts, PWM system may cost less. Over ~800 Watts, an MPPT system usually will cost less and be easier to source + wire.

    As said above--Really like to start with your loads first--Then paper design the basic system. Then finally configure a system and specify the components. Just to give you an idea:
    • 500 Watt*Hours per day (~42 Amp*Hour @ 12 volt per day) = Minimum system (LED lights, cell phone charger, radio)
    • 1,000 WH per day = Nice off grid cabin size. Use propane for cooking/heating/hot water, RV pump for water pressure.
    • 3,300 WH per day = Near normal off grid electric life style. Refrigerator, lights, well pump, clothes washer, computer, etc (very conservation minded).
    You can always use a small genset (Honda eu1000i or eu2000i or equivalent) for powering electric tools and such--Just use the solar for lighting, cell phone charging, and other "quiet time" activities.

    In a few years, if your usage justifies, you can now measure your loads (i.e., from genset) and design a larger system. I would suggest that weekend/seasonal use frequently a genset is less costly 9+ months of full time off grid use can justify going "full" off grid solar (plus genset backup).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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