question for crewzer

sawmill
sawmill Solar Expert Posts: 93 ✭✭✭
in Advanced Solar Electric Technical Forum #1
I had read in another post by Crewzer where he had changed his park mpp(mx60) from 77% to 80%. I wonder if he or others could go into detail about this setting and explain how to figure which setting is more efficient for different arrays.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #2
    Re: question for crewzer

    Sawmill,

    The MX60 controller’s active MPPT function does not operate when the controller’s output current is < 5 A. This info is contained in the manual. Instead, the MX60 sets the array voltage at the array Voc times the % setting in the "U-Pick” menu.

    The OutBack factory default "U-Pick" setting is 77%. I found early on that I could increase bulk stage “< 5A” output current by increasing the “U-Pick” % setting to something in the 80% to 85% range.

    Further research has led me to question the 77% default value. I looked at the specs for a dozen or so PV modules in the ~120 W STC to 200 W STC range, and I found the average full-power Vmp-to-Voc factor to be ~80%. I'll see if I can find my report and post it later.

    You can experiment with this setting for your system by entering different “U-pick” values and see which works best for you. You just need to conduct your experiments when controller output current is <5 A and the controller is operating in bulk mode.

    HTH,
    Jim / crewzer
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #3
    Re: question for crewzer

    I'll take a stab at this one,

    If one looks a an IV curve, being off a few percent LOW on the voltage has less of a loss than being a few percent HIGH on the voltage.

    Current goes from 0 to about 95% of maximum current from VOC to VMP, but it does this in only ~20% of VOC value. So if the MX60 parks 5% low from the true vmp, thats 5% less voltage at maximum current vs, 5% more voltage at possibly 20-30% less current.

    The technical term for this is fill factor and thin film is very different than Si and Single Si vs Mono Si have differnences as well. Further irradiance level moves this further ( lower % wise at values less than 1000wmsq )

    I use 78% of VOC in my products for the initial instant turn on and track from that point on.
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  • sawmill
    sawmill Solar Expert Posts: 93 ✭✭✭
    #4
    Re: question for crewzer

    Many thanks to Solar Guppy and Crewzer for taking the time to explain this function especially in a manner that those of us who are somewhat electonically challenged can understand.
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  • backroad
    backroad Solar Expert Posts: 185 ✭✭
    #5
    Re: question for crewzer

    Huh? :):) :):):)
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #6
    Re: question for crewzer

    Duplicate post;)

    Ralph
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #7
    Re: question for crewzer
    crewzer wrote: »
    Sawmill,

    The MX60 controller’s active MPPT function does not operate when the controller’s output current is < 5 A. This info is contained in the manual. Instead, the MX60 sets the array voltage at the array Voc times the % setting in the "U-Pick” menu.

    HTH,
    Jim / crewzer

    I'm surprised they haven't changed that mode/method of operation by now.

    boB :D
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