switching PV panels from series to parallel

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System
System Posts: 2,511 admin
in Advanced Solar Electric Technical Forum #1
Ok, folks...hope you can help. I've built 2 PV panels from ebay cells. 1 is mono, the other is poly. Both panels appx 196W. (49 6x6 8A 1/2V cells in series...7 strings of 7 cells) At max. output, I'll get 24.5VDC @ 8A from each. My GTI turns on @ 14 VDC, & it's max input is 28VDC. (300w constant, 600w peak rating).In low light, I'm not making enough voltage to turn on my GTI (both panels are hooked to the GTI in parallel) What I'd LIKE to do is find a switch or relay that will automatically switch my panels to series when light is low (dawn, dusk, cloudy day, etc.), & then back to parallel when the voltage rises enough to keep the GTI on line. Somebody told me that he thought a solid-state charge controller could do this, but he wasn't 100% sure. Thanks in advance....Doug
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,443 admin
    #2
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    Re: switching PV panels from series to parallel

    Solar panels are pretty much current devices... Once you have minimum light (weak direct sun for example)--the output voltage pretty much Hits Vmp--Then, the more sun, the more current the controller can pull...

    Doing the series/parallel connection for "low light" conditions will not gather any more power--If there is not enough light to maintain something close to rated Vmp--then there is nothing you can do to get the current/power.

    Does your GTI have an MPPT front end of some sort? Or was it designed to run on a battery bank (basically fixed voltage/unlimited current)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #3
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    Re: switching PV panels from series to parallel

    yes, it's MPPT...300/600 "Power Jack" I got on ebay.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #4
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    Re: switching PV panels from series to parallel

    I don't know of any those that are MPPT, do you have an actual brand/model number?

    But regardless, very doubtful that any switching method would work, as it is the amperage that drops in low light, not the panel voltage.
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  • System2
    System2 Posts: 6,290 admin
    #5
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    Re: switching PV panels from series to parallel

    as far as the brand, it's a "Power Jack"..if you do an ebay search for "grid tie inverter", you'll see a couple dozen of theese. The specs are in the ebay ad. I don't know...maybe I am chasing with this...just trying to keep the GTI outputting power for as long as possible...I'm open to any & all ideas about how to do this...Thanks...Doug
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