Did I get the panels I paid for?

solarnewbie440
solarnewbie440 Registered Users Posts: 2 ✭
in General Solar Power Topics #1
Hi: My first post!!! New install: I am supposed to have 435 watt panels, but the data logger shows as the total as tho they were each 425 watts. Could this be that because the house faces SSE, so that the panels face the sun at SSW, accounting for the slight loss? Or did I not get the 435 watt panels? Looked for a sticker on the backside with a mirror but did not see any, tho I do not want to lift one up to give a thorough look for obvious reasons.
I don't want to hassle the installer unless the answer is obvious. Reading was 1 PM full sun: 0.367kw average per panel.
Thanks for your help and excuse my ignorance.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    solarnewbie440 said:
    Hi: My first post!!! New install: I am supposed to have 435 watt panels, but the data logger shows as the total as tho they were each 425 watts. 
    I don't know what the 'data logger' is, but would think the info would have to be manually entered.
    solarnewbie440 said:
    I don't want to hassle the installer unless the answer is obvious. Reading was 1 PM full sun: 0.367kw average per panel.
    This is fine. Panels are rated in a 'flash' test (Standard Test Conditions, STC) and not allowed to warm up. There is also a Normal Operating Cell Temperature NOCT value which is typically about 75% of the STC. So 367/435 = about 84%, Which is very good.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    As Photowhit says--Those are basically "marketing" numbers. As cells get hot, their Vmp (voltage maximum power) falls. Pmp=Vmp*Imp -- Imp changes a little (actually rises a bit as panels heat up)--But the change is small enough that we normally ignore Imp-Hot/Cold changes.

    Here is a thread that talks about how solar panels "work" in our systems:

    https://forum.solar-electric.com/discussion/5458/two-strings-in-parallel-with-unequal-string-voltages

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solarnewbie440
    solarnewbie440 Registered Users Posts: 2 ✭
    #4
    Hello: The data logger (PSV6) is an interface that connects to the L1 and L2 cables in main breaker box & elsewhere to provide info on the voltages being used, how much is being generated by the solar system, and how much comes/goes from or to the utility that you read out on their app. I did notice on the contract specs that the system is rated 3.92KWp (DC), while the output is shown as peak AC output of 3.34KWp, so maybe it's just semantics. Panels are Maxeon gen 6, hopefully M435's, and not M425's.
    Thanks, I appreciate your input.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #5
    The ability to detect real world differences between 435 and 425 panels will be difficult . 
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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