merging panels. old and new

kamchukakamchuka Registered Users Posts: 51 ✭✭
just wanted to ask before i started throwing sparks. I have 4 older 75 watt panels now (not sure brand). I just purchased 2 new 200 watt evergreen panels and a new 60 amp mppt controller. can someone give me a holler if this set up will not play well with each other. heres what i plan to do....or was told to do, but doesnt sound right to me.
old) 75 watt, open circuit votage of 21.7, rated 17.0
new) 200w, VOC 35.0 Vmp 28.3
 4 old panels series/parallel 2 and 2. 2 new in series, then wire both sets in series into one controller. 
I was going to leave current system in place and wire new panels into new controller and straight to battery bank. 

magnum 2k (12v)
1400ish ah fork lift battery

thanks in advance, jim
700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 

Comments

  • mike95490mike95490 Solar Expert Posts: 7,249 ✭✭✭✭
    So here's the rules.
    Panels in parallel :  Vmp needs to be +- 10% of each other
    Panels in series : Imp needs to be +- 10% of each other
     You will need to look at the stickers on the back of the panels and see what they say.

    so
    >  4 old panels series/parallel 2 and 2. 2 new in series, then wire both sets in series into one controller. 
    is not perfect.   I would use the 4 old  as you describe, and then wire the new 200w both in parallel
    75w   2s,2p
    parallel with
    200w
    200w
     That gives you 4 strings, so you should use a protected combiner box.


    But no matter how you wire those panels, you are way under paneled for the battery, and it will die of Stratification long before you can wear it out.

    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 ,

  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    i supplement power with the genny. laundry every 3-4 days. thats a 4-7 hour burn depending on DOD and the dirtyness of the work ive been doing. i charge them at 100+ amps, all 4 stages. im hoping to extend this to a week, if my wife can take the smell! 
    correct me if im wrong but isnt that 3 strings? 2x24v into old controller and one 48v into new controller.
    thanks man! post is in the ground and we have good sun today so I'll install everything and make real good friends with my volt meter.....see what happens.
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • BB.BB. Super Moderators Posts: 26,758 admin
    Depends on how far off "optimum" you want to aim for.

    Your 4 old panels are Vmp~18 volts (or 17.5 volts). Two in series is Vmp~36 volts. That is find for a PWM charge controller on a 24 volt battery bank... You have a 12 volt battery bank? So, you would use 4x Vmp~18 volt panels in parallel with a PWM charge controller. Or you can put 2 series * 2 parallel and an MPPT type charge controller to down convert to 12 volt battery bank (Vbat~15 volts).

    The 200 Watt panels are Vmp~28 volts. That is too high of voltage for a PWM controller to charge a 12 volt battery bank. And too low of voltage to charge a 24 volt battery bank (need Vmp-array35-40 volts for a PWM controller). If you put two panels in series, that would give you Vmp-array~56 volts and you could use an MPPT controller for 24 volt battery bank.

    Assuming you have a 12 volt battery bank, your Vmp~28 volt panels in parallel (or even series) to a MPPT controller to charge the 12 volt battery bank would be fine.

    Now, you have Vmp~18 volt panels an Vmp~28 volt panels... You cannot (efficiently) put the sets of panels in any "useful" series/parallel combination that would be "efficient" at generating power for you.

    However, I have a question, can you confirm the 200 Watt Evergreen panels you have? They may be Vmp~18 volt or Vmp~18/36 volt (configurable) panels. If so, that is a different answer (you can parallel all of the Vmp~18 volt panels to a PWM controller very nicely) or series/parallel them for Vmp~36 volt array into a MPPT controller to your 12 volt battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    Thanks Bill!
    Heres where im at. everything is in the air and I have wired the old set in series to gain 80-83 (confirmed) volts. Now the new set is pumping out 65-70 in series. the theory was wire the 2 in P and straight to a 60 amp MPPT charge controller but with the volts being so far apart ???
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • BB.BB. Super Moderators Posts: 26,758 admin
    edited October 2 #6
    There is no optimum Vmp  voltage. What Vmp-array voltage should the mppt controller pick. What voltage will the mppt controller pick?
    At this point, see what you get.

    (4x75w + 2x200w)*0.77 controller&panel deratings = 539 watt typical best harvest  peak

    Into a partially charged battery back (and or DC loads) around noon on a clear sunny day.

    If you get within 85-90% of that value, you are doing fine. If you get 1/2 that amount, need to look at things closer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    old hollywood bed frame and scrap steel'll get it done. plugged it all in, volts from old panels dropped to match the new ones (65) in the shade.
    i got 21 amps durring a burst of sun and they were partially shaded...not to shabby! I'll know tomorrow what the real deal is.
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    I cant get 5 minutes of sun!!!! anyways i'm getting up to 28 amp bursts in overcast! hovering around 20 amps. pretty dadgum happy with that. my old panels and controller were topping out at 16 amps under full face melting sun.
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • BB.BB. Super Moderators Posts: 26,758 admin
    28 amps × 14.0 volts = 392 watts....

    Getting there.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    35 amps in direct sun. I'll get 2 more panels in Nov and be done. I need 2 kw a day and that will do even through winter...mostly 
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
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