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Need help with Siemens SP75 solar panel

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  • Need help with Siemens SP75 solar panel

    I bought 5ea of these used 75w panels and want to run a koi pond. The panels are 17v with 4.4 amp output. Anyone has info how to parallel these panels and what controller to be used so I can connect to my 900w inverter to run a AC pump and UV sterilizer? The pump and uv light are under 100w. Thx
    Last edited by gfong; 04-03-2018, 11:44 PM.

  • #2
    Sadly, you need one more panel, or only use 4.
    The 17V panels will not allow for a healthy battery, usually 18-22V are needed. So the panels need to be wired 2 in Series, and then two series strings wired in parallel 2S2P
    This would give you about 35V which would need a small MPPT controller to downconvert to charge a 12V battery.

    The risk of using a 17v panel in parallel with a PWM controller, is that you will never quite fully charge the batteries and they will slowly degrade.
    Powerfab top of pole PV mount (2) | 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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    • #3
      Thanks Mike. Can I just run 5 parallel which will give me 17V and about 22amps, then goes to a controller to drop to 12v, then hook up a inverter to 110 AC so I can run AC pump and AC UV light? I was thinking to run everything in DC, but I don't see DC UV lights for pond. I am not plan to run it at night so I am not charging to battery.

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      • #4
        You can - BUT After 17V goes through a controller, you only have about 15V to work with. That will charge a battery to almost 95% on a cold day. On a warm or hot day, as the PV panel voltage sags from the heat, you will seldom complete a charge cycle, and slowly kill the batteries.

        17V is such an odd number, because it is not useful as a single panel. Normally, panels are rated 18-19V for 12V charging. So if you are in a cool area, never deeply drain the batteries, you might eek by with what you have. But when outdoor temps get over 80F, you are not going to get 17V anymore. Keep a close eye on the system voltages.
        Powerfab top of pole PV mount (2) | 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

        Comment


        • #5
          Siemens 75 watt panel.JPG Here's a data label from a SP-75. It is a 36 cell 12 volt panel. Older lower efficiency cells, still considered a 12 volt panel though. I would imagine, in real hot climate the voltage might get too low to equalize a battery
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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