How to check panels

castilloj
castilloj Solar Expert Posts: 208 ✭
in Solar Beginners Corner #1
Hey guys, what is it called when you hook up a voltmeter to the negative and positive of a solar panel not facing the sun?
is it VOC?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: How to check panels

    It's called "a waste of time". :p

    But seriously. Voc is Voltage open circuit. A panel will produce this (but no current) with the merest amount of illumination. There should be nothing connected to the panel leads except the meter.

    It also doesn't tell you much other than that the panel has a Voc of 'X'. Panels can actually make their specified Voc without being able to produce their full current. That's why it is better to test for Isc to see if the panel is any good. To do this you need a meter capable of taking the full current of the panel (for example if the Isc rating is 8 Amps the meter should be able to read 10 or more). And you need full, direct sun.
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #3
    Re: How to check panels

    Im trying to hook up My 9 Photo watts again with my 6 Astros panels again, so i wanted to make sure each panel is working at its maximum.
    right now i have the 9 Photowatts and mppt is showing-
    Array Voltage-90.75v
    sweep vmp- 90.70v
    sweep VOC-112.07v
    sweep pmax-149watts
    and its a very cloudy day.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: How to check panels

    What Cariboocoot said. Check one panel at a time and that will tell you if they are any good. Checking voltage alone, sun or no sun, will NOT give you the answer you need to be looking for. What Cariboocoot said is the proper way to find good from bad panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #5
    Re: How to check panels

    And I will keep pushing the inexpensive DC Current Clamp Meter--Perfect for finding strings that are not carrying their share. Just put the "clamp" across one wire for each string and measure.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: How to check panels
    BB. wrote: »
    And I will keep pushing the inexpensive DC Current Clamp Meter--Perfect for finding strings that are not carrying their share. Just put the "clamp" across one wire for each string and measure.

    -Bill

    Anyone know how to get one of those in Canada? Not in the store or on-line that I can find.
    I know; buy it in the States and pay the mega-$ to bring it in. NAFTA? Whazzat? :cry:
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #7
    Re: How to check panels
    Cariboocoot wrote: »
    Anyone know how to get one of those in Canada? Not in the store or on-line that I can find.
    I know; buy it in the States and pay the mega-$ to bring it in. NAFTA? Whazzat? :cry:

    I ordered mine online using a link to Sears (international) that I believe BB posted one time. Arrived as if it was shipped from a local Sears outlet.

    Edit: Just checked the link he posted below and it does, after a few seconds state: "Now shipping to Canada". Likely the same link I used.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #8
    Re: How to check panels
    Cariboocoot wrote: »
    buy it in the States and pay the mega-$ to bring it in. NAFTA? Whazzat? :cry:

    That's what I'm thinking re ordering in a couple of Midnight lightening surge suppressors :( - - - but for whatever reason, they didn't nail me when I ordered in my clamp meter. Perhaps the border guards were asleep? lol
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: How to check panels

    My foray into the Canadian site netted a listing of "Extech 80A Mini AC/DC Clamp Meter $149.41" with no details for some reason. It comes from the US. Of course shipping and extortion fees (like the 12% HST) are extra. :grr

    Altogether now: "O, Canada ..." :roll:
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  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    #10
    Re: How to check panels

    I use an old Radio Shack DVM that has a 20A rating for testing panels. This one is a Kyocera 135W model:

    dscn6043.jpg

    Also use an Extech 40/400A clamp-on Ammeter. Great product.

    iota75a.jpg

    I generally use the DVM to measure each panel before installation, then use the clamp-on meter to measure strings of panels.

    I brought a 15W panel and two small muffin fans as a show-n-tell to work. When the panel is in full sun, it would bring both fans up to full speed. Indoors, the open circuit voltage was still about 21V, but there was no current available under the fluorescent lights.
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #11
    Re: How to check panels

    COOT, C tire has them but unknown quality $ 60
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: How to check panels

    I don't find anything on their web site, so I'll have a look next time I'm there. Another reason to go to CT! Hurrah! :p

    Thanks, Eric. :D
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #13
    Re: How to check panels

    yup was hanging on the rack beside multi meters
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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