Need help on a few things for off grid solar setup

24

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  • PhotowhitPhotowhit Solar Expert Posts: 5,022 ✭✭✭✭
    edited April 2016 #32

    In a 48 volt system, my guess is you will be fine with 10 gauge, In you are combining at the array and running a single set of wires to your charge controller, you will be around 70 volts 28 amps. Looks like 8 gauge will Bring you in for a 3 percent drop. The voltage from the panels will drop off in the heat but should keep you in the charging range for a PWM charge controller. This is where the advantage of an MPPT type charge controller can help, you typically want your incoming voltage to be around 2x the charging voltage. So your wires would typically carry around 120 volts (4 - 60 cell panels in series) That will carry 30 amps on 10 gauge wire with a 3% loss or output from a 4000 watt array. Though this might get you close to dangerous VOC numbers.

    Mid Missouri here. Only problem I've had is I quit getting the batteries for my emergency radio for the Nuke plant down the road. They use the power companies address list!

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Personally I use genasun and Morningstar MPPT.
    When they say that they are 97% to 98% efficient they mean it.
    I measured input and output power and those were the numbers I got. 

    For a 60 foot run go with the highest voltage that you can. With the Morningstar you can run up to 80 or 90 OCV on the solar panel side to charge a 12 or 24 volt bank. But if you go with the highest allowable input voltage to charge a 12 volt bank efficiency will drop a few percent.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • justinleejustinlee Registered Users Posts: 53 ✭✭
    as far as mixing the panels what do I need to be looking for.I have to 24 volt panels that could make 48 two parallel with my 48 volt system with the 16 12 volt panels but how do I know these will be compatible what do I need to look for thanks
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    More or less, for series connected panels, you want the Imp to be within 10% of each other (i.e., 5 amps and 5.5 amps maximum difference).

    And for parallel connections, you want the Vmp of the parallel panels/strings to be within 10% of each other too (i.e., 72 volts and 79 volts).

    To be clear a "24 volt panel" in our "battery world" terms is Vmp~36 volts (or ~35 to ~38 to ~40 volts). This would allow you to use a PWM controller from your "24 volt array" (again Vmp~36 volts) to your 24 volt battery bank.

    Many "24 volt" panels are really Grid Tied type panels with Vmp~30 volts--That is too low of voltage to have a single panel effectively charge a 24 volt battery bank.

    However, if you have Vmp~30 panel, you can put two in series for Vmp-array~60 volts, and use an MPPT type charge controller to take the "high voltage/low current" of the solar array and efficiently down convert to "low voltage/high current" needed to charge the 24 volt battery bank.

    So, do you have a mix of panels today (or looking at buying). Exactly what is each type of panel's Vmp/Imp ratings. And what charge controller are you thinking of using (and is this a 48 volt Lead Acid battery bank)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    well I have 2 extra panels that I had from before that we're 24 volt each and I figured 2424 is 48they are 16.9 amps I believe at 230 watts each. is it possible to run those into those original panels I was telling you about if I wired those in 48
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    Those watts and amp numbers do not make sense.

    If it was 230 watts, 8.45 amps, then
    230w / 8.45a = 26.9 volts Vmp

    A typical 230 watt panel is Vmp~30 volt panel and
    230w / 30v = 7.67 amps

    What voltage battery bank do you want to run (and AH rating)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    yeah I believe you're right...I am out here today so I'm going to walk over there and get the numbers off the back of them I believe there around 8 amps a piece with a total of 16 amps that's what I was thinking...I have those 16 12 volt panels that I'm setting up and I also have these 24 volt panels and that's what I was wondering if they were compatible if I wired the 24 volt panels in 48 as I am going to wear these 16 12 volt panels in four rows of 48.if I could run those together it would be nice.I have definitely made up my mind that I'm going with 48 volt system this is why I bring this up
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    the panels are sharp solar module.. ND-u2 30q2bx
  • VicVic Solar Expert Posts: 2,975 ✭✭✭✭
    edited April 2016 #40

    Hi justinlee,

    You said,  "   ...   I also have these 24 volt panels and that's what I was wondering if they were compatible if I wired the 24 volt panels in 48   ... "

    As BB Bill,  and believe Photowhit noted before,  these PVs are NOT,    NOT  24 V PVs.   They ARE 60 Cell PVs,  with a Vmp (the voltage rating that matters most for compatibility) of about 30 volts.

    REAL 24 V PVs have a Vmp from about 35 - 37 volts.   Those Sharp PVs have a Vmp of about 15% lower than any REAL 12 V PVs,  wired in series,  in your case,  wired in strings of four 12 V PVs,  compared to strings of two of the 230 Watt Sharp PVs.

    Two of those Sharps  will not have sufficient output voltage to contribute any real charging.

    EDIT:  Did search for a similar number to what you posted above,  and even eliminating the space between the 2 and 3 (these are 230 watt PVs,  would bet),  still there are no hits on that number ...   but almost all 230-ish watt PVs ARE 60 Cells,  and that makes the Vmp between about 29.5 and 30.7 V.   Generally the Poly PVs having Vmps in the lower part of that range ...

    Not to try to be too assertive ...   FWIW,   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.
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    okay that being said what about wiring those two panels in 48 and putting them on a separate charge controller and then going to the same battery Bank..or does the same issue come into play no Matter a separate charge controller or not
  • VicVic Solar Expert Posts: 2,975 ✭✭✭✭
    edited April 2016 #42

    Hi justinlee,

    Could you please confirm the model number of those tow Sharp PVs?   There are a number of Sharp 230 watt PV model numbers,  and it would really be good to be speaking about the exact PVs that you have   ...

    OR,  could you please note what the label on the rear of each of these PVs says for the Vmp,  and Imp,  and good to confirm that each of these two PVs are identical ...

    Thanks,   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.
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    Pmax 230.0 w. VOC 37.1. Isc 8.48 amp. Vpmax 7.67 a. Ipmax 600 v. Max system voltage 600v. Max series fuse 15 a
  • VicVic Solar Expert Posts: 2,975 ✭✭✭✭

    Hi justinlee,

    Thanks for the data on those Sharp 230 W PVs.  Doing the calc,  looks like with 230 W,  and the noted Imp of 7.67A,  that the Vmp is very close to 30.00 Volts (29.99 V).  And in poking around on the net,  looks like that the ap-130s have a surprisingly high Vmp of about 18.9 V.  So two of those in series yields about 37.8 V string Vmp.  This difference is quite large,  more than 20 %,  so these two types of PVs will probably not work at all well together.

    Furthermore,  the String Vmp of the two Sharp 230s will be 60 volts,  which will mostly be insufficient to add much charge for a 48 volt battery,  especially a Flooded battery..

    This may not be worth the effort to try using the Sharps with the APs.   We do not yet know what type of Charge Controller (CC) that you will wind up using,  but even with a PWM CC,   it seems that the contribution of the Sharp PVs will be fairly small,   IMO.

    FWIW,    Thanks for the info,   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.
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    I have another question.... At what point in how many amps or batteries or panels wired together do I have to start being concerned about getting an electrical shock while wiring this up.... For example if I had 16 6 volt batteries wired in two sets of 48 paralleled.... How dangerous would it or could it be to service the batteries and accidentally touch the positive and negative at the same time with the combined increased amps..... Or better yet the solar panels combined into 48 volts knowing my total will be 27 amps or so
  • PhotowhitPhotowhit Solar Expert Posts: 5,022 ✭✭✭✭

    48volt can be dangerous, but just treat it all like it will kill you!

    understand that there is no trouble working when the circuit is not complete. Run your panels in series to a breaker that is open, then close the breaker when you're ready to initiate your system. When I here about big arcs I cringe. I believe you will need a combiner box for the strings of panels as well. 

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    So just the wiring of the battery Banks separate from the solar can also be a danger I guess?
  • PhotowhitPhotowhit Solar Expert Posts: 5,022 ✭✭✭✭
    justinlee said:
    So just the wiring of the battery Banks separate from the solar can also be a danger I guess?

    Yes, I forgot about having 4 strings of batteries, I don't like having that many paralleled strings. I'd suggest using a buss bar system, and go ahead and put breakers or fuses on each string. Major pain... I think you are likely to end up with a 48 volt system. I'd suggest biting the bullet and do it now. You can sell the inverter as new, and I think Magnum will honor their warranty from the date of manufacture if someone doesn't have a receipt. I'd ask them directly, It's not a huge group of people and it would be worth asking. Heck if I wasn't hanging in there with my 1800 watt inverter and waiting to see Midnight's Best of all worlds inverter. I'd be interested!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    You lost me sir on the Magnum inverter I don't have one... I'm confused?
  • Raj174Raj174 Solar Expert Posts: 706 ✭✭✭✭
    Just another precaution, if using tools, like screwdrivers, pliers, and wrenches on electrical connections, they should be coated with a rubber or plastic polymer or wrapped with electrical tape. A short with a metal tool when working on DC can cause a really large arc, and it can happen way faster than you can move.  
    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 195AH LiFePO4 no BMS, 4500W genset.
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    Thanks...also my official footage from the panels to the charge controller going to be located in the house is 55 feet..48 volts @27 amps @ 55 feet.......am I still looking for 8 gauge or 6?
  • PhotowhitPhotowhit Solar Expert Posts: 5,022 ✭✭✭✭
    justinlee said:
    You lost me sir on the Magnum inverter I don't have one... I'm confused?

    Sorry mixed threads up...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • Raj174Raj174 Solar Expert Posts: 706 ✭✭✭✭
    edited April 2016 #53
    The PV voltage is over 70 volts right? If the PV voltage is not at least 70 volts then you might have problems charging a 48 volt battery bank.
    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 195AH LiFePO4 no BMS, 4500W genset.
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    They are 12 v 18.9 on open circuit ...is that the number your looking for?
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    18.9 Voc (voltage open circuit) is a bit "odd"... Nominally Voc would be >21 VDC and Vmp would be ~17.5-19.0 volts for a "12 volt" battery charging solar panel.

    Vmp falls as panels get hot... If you have cool batteries and very hot weather--Vmp-array of 70 volts is starting to skirt the edge of "efficient/proper" charging on hot days.

    Are you sure that Voc~18.9 VDC? (voltage open circuit)

    I would guess that Vmp~18.9 VDC is more likely (and much more standard for voltage maximum power).

    Using a voltage drop calculator:

    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=48&phase=dc&noofconductor=1&distance=55&distanceunit=feet&amperes=27&x=70&y=10

    Voltage drop: 1.87
    Voltage drop percentage: 3.90%
    Voltage at the end: 46.13

    That is based on 48 volts... If your array was Vmp-array~18 volts or 72 volts for four panels in series:

    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=72&phase=dc&noofconductor=1&distance=55&distanceunit=feet&amperes=27&x=63&y=4

    Voltage drop: 1.87
    Voltage drop percentage: 2.60%
    Voltage at the end: 70.13

    And 8 AWG wire would be OK. We recommend around 1% to 3% voltage drop--You are getting close to 3% drop.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    my plan is to buy the 48 volt 2000 watt Aims pure sine inverter charger.....what about this charge controler here for my set up?...Aims 60A MPPT Solar Charge Controller scc60mppt
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    BB. said:
    18.9 Voc (voltage open circuit) is a bit "odd"... Nominally Voc would be >21 VDC and Vmp would be ~17.5-19.0 volts for a "12 volt" battery charging solar panel.

    Vmp falls as panels get hot... If you have cool batteries and very hot weather--Vmp-array of 70 volts is starting to skirt the edge of "efficient/proper" charging on hot days.

    Are you sure that Voc~18.9 VDC? (voltage open circuit)

    I would guess that Vmp~18.9 VDC is more likely (and much more standard for voltage maximum power).

    Using a voltage drop calculator:

    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=48&phase=dc&noofconductor=1&distance=55&distanceunit=feet&amperes=27&x=70&y=10

    Voltage drop: 1.87
    Voltage drop percentage: 3.90%
    Voltage at the end: 46.13

    That is based on 48 volts... If your array was Vmp-array~18 volts or 72 volts for four panels in series:

    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=72&phase=dc&noofconductor=1&distance=55&distanceunit=feet&amperes=27&x=63&y=4

    Voltage drop: 1.87
    Voltage drop percentage: 2.60%
    Voltage at the end: 70.13

    And 8 AWG wire would be OK. We recommend around 1% to 3% voltage drop--You are getting close to 3% drop.

    -Bill

    rated voltage is 18.9...open circuit voltage 24.6...
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    Ok. That makes more sense and is what you want.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • justinleejustinlee Registered Users Posts: 53 ✭✭
    Aims 60A MPPT Solar Charge Controller scc60mppt ??     any good for my system??....and this  eMGCByXGxVw6-1ymwDC9q4EaAuA38P8HAQ
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