Array with different panel voltages

fergussonfergusson Registered Users Posts: 4
edited October 2019 in Solar Beginners Corner #1
i have been at this for 28 years and there is always a new question 
i have a 12 volt system dumb I know changing soon
some panels are 21volts and some are 26 volts is it ok to mix them ?
or are some canceling out others?
 Thank you 
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Comments

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    They are not “canceling” each other out, but like battery voltage, they will seek the lowest voltage in the string.  I assume your “Papal” voltage is not some devine inspiration?

    tony
  • BB.BB. Super Moderators, Administrators Posts: 32,023 admin
    What kind of charge controller? PWM would be fine... The Vmp-26 volt panels will produce a few Watts less.

    Are you taking about Voc or Vmp for the panels?

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • fergussonfergusson Registered Users Posts: 4
    I have some very old controllers
    and I don’t know what VOC or VOM is
    i am happy they aren’t canceling out I was told they were 
    im just not getting the Amps that I should out of each array I have three
    80 Amps 50 Amps and 60 Amps
    they aren’t putting that out
    thank you for you very prompt answers
    tri star controlers 
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited October 2019 #5
    It depends on details, but you might be losing 10% of the watts of the 26V panels or 5% of total watts (as compared to the case of all panels being the same voltage).

    I am available for custom hardware/firmware development

  • fergussonfergusson Registered Users Posts: 4
    I loosing a lot more than that
    ive been at this for quite a while it seems like I know nothing
    thank you
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    Have you tried checking to see if there are specific panel(s) underproducing? 

    Generally, you should get ~75% of rated amps in full sun with proper tilt, and enough of a load to use the current.  With 190a total, that's ~140-150a of load.  What is your load (eg if battery charging, what size bank in amp-hours, and what type batteries (eg flooded lead acid,))?

    A clamp-on DC amp meter is handy for debugging problems like this.  Absent that, you could try covering individual panels with a tarp or whatever and watch output to get a rough idea.  
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators, Administrators Posts: 32,023 admin
    We really do need to know details... All panels connected in parallel to the controller(s)?

    As Estragon suggested, you can cover one panel at a time and see how the system responds (batteries should need charging, or you have some loads connected, such as an electric heater, so the controller is outputting its maximum current.

    Also, can you tell us the voltage at the Vpanel input of the controller(s) and the Vbatt output voltage?

    And, for better/easier debugging of any DC power system, getting a DC Current Clamp Meter (Digital multi-meter) will help a lot--Very nice to have if you are going to work with DC (and AC) power systems very often.

    A decent DC/AC Current Clamp DMM is around $100 (USD) and you can find ones that are "good enough" for $50 or less:

    https://www.amazon.com/gp/product/B019CY4FB4 ($100)
    https://www.amazon.com/gp/product/B07546L9RT ($50)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,023 admin
    I should add there are AC only Current Camp DMMs (with DC voltage measurement capabilities). These are perfectly good meters...

    However, they cannot measure DC current and are not useful for our DC needs.

    Be careful when reading the product descriptions... They can be a bit confusing at times.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2littleharbor2 Solar Expert Posts: 1,628 ✭✭✭✭
    Look in the specs and you need to see a DC current rating along with an Ac rating. If no DC rating move on.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • fergussonfergusson Registered Users Posts: 4
    Well guys we don’t need to worry any longer the house burned down yesterday 
    because I bought a cheap controller it started the fire
  • mike_smike_s Registered Users Posts: 133 ✭✭
    In parallel, with a PWM controller, you're not losing anything. They're all running at battery voltage. A mix of panel voltages doesn't change that.

    Parallel, with MPPT, some won't be running at peak efficiency.

    Series, with MPPT, it's the difference in I(mp) current that matters, not voltage.

    Sorry about the house. I hope you're joking.
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    fergusson said:
    Well guys we don’t need to worry any longer the house burned down yesterday 
    because I bought a cheap controller it started the fire
    Oh boy, I hope that's just a figure of speech or a joke.   It's also a reason to have the power gear NOT in the main house.
    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 ,

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