Use of buck converter

BartmanBartman Registered Users Posts: 3
Would there be any advantage to using 24v panels, then using a buck converter to step it down to 12v. Could I make better use of the area available on my roof and produce more wattage for 12v part of system? 

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,053 admin
    I have not heard of anybody trying it... Could possibly work with a PWM charge controller--But you are mixing/matching a buck converter to a PWM solar charge controller. I am not sure that it would be stable for the long term.

    Normally, you would use an MPPT type charge controller--Internally, an MPPT charge controller is (almost always) a computer controlled Buck Converter... Designed to do exactly what you want (although, at a fairly expensive price).

    What is the array Wattage you plan on connecting?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BartmanBartman Registered Users Posts: 3
    I was looking at this buck converter and was open to any size array you could suggest. I was hoping to use an MPPT.

    $138.00$138.00
    Size : 24V TO 12V 100A 1200W
  • BartmanBartman Registered Users Posts: 3

    I like your panels, I probably will be leaving this to the experts. 


    Canadian Solar CS3K-310MS Monocrystalline 310 Watt Solar Panel with Black Frame


  • BB.BB. Super Moderators, Administrators Posts: 30,053 admin
    I actually do not work for our host Northern Arizona Wind & Sun... I am just a volunteer here. Pretty much everyone is volunteering their time and knowledge to help others.

    Regarding your questions... There are several ways to answer you. First, you measure/tell us the loads you want to run and (roughly) where the system will be installed (hours of sun by season), and how you will be using the system (weekend cabin, full time off grid, etc.). Or, you tell us a part of your system (size of battery bank, size of solar array/area where panels can fit, etc.).

    In any case, I highly suggest that do some paper design of your system (different options), to size the components--Then figure out which combination of components will meet your needs/cost point.

    Mixing and matching components from things you have already purchased is usually difficult, and something will simply not fit.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,613 ✭✭✭✭✭
    A simple Buck converter is not likely to work well off of solar, for the long term.  Many factors cause solar power to fluctuate and that will drive a simple buck converter nuts.
    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 ,

  • EstragonEstragon Registered Users Posts: 4,451 ✭✭✭✭✭
    Bartman said:
    I was looking at this buck converter and was open to any size array you could suggest. I was hoping to use an MPPT.

    $138.00$138.00
    Size : 24V TO 12V 100A 1200W
    To clarify, if using an mppt charge controller you don't need a buck converter.  Mppt controllers internally buck voltage down to battery charging voltage. 

    In addition to being able to use larger panels, most can buck down from higher voltage series strings of panels, which can save on voltage drop and wiring costs if there's much distance from pv array to controller..


    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
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Bartman said:
    I was looking at this buck converter and was open to any size array you could suggest. I was hoping to use an MPPT.

    Then you don't need a buck converter.
  • NANOcontrolNANOcontrol Registered Users Posts: 169 ✭✭✭
    I do it, I'm using a modified buck right now on my system.  A MPPT controller is just a modified buck. That voltage converter will not work because the output is likely fixed at 12.0V and that voltage will not charge a battery. Also you need to maintain at least a minimum voltage on your panels. Otherwise the buck converter will drag the panels voltage down and there will be even less power. If you are asking the question here, it is likely you do not have the skill set to do these modifications.
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