Minimum voltage from a PV

westbranch
westbranch Solar Expert Posts: 5,183 ✭✭✭✭
in General Solar Power Topics #1
Is there a place to locate the minimum voltage a PV panel will output? Not found on the Man. site for my panels. Does it exist or ?

ie does a 12 v panel produce less than the 12 v at any time, for instance in early morning before sunrise?

I have noted my SB 2000e kicks in in the morning and it is always at or just above the overnight resting voltage, as it should be and that is when the reverse flow relay is activated. Its activation point is for > .1 A input from the PVs, the unit consumes .1 A

So I was wondering if there is lower V that is being created for a small period of time but not able to be seen on the CC display as it displays Batt volts...

Cheers
Eric
 
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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Comments

  • System2
    System2 Posts: 6,290 admin
    #2
    Re: Minimum voltage from a PV

    Not that I know of. Not sure where you're headed with this question, but a typically "12 volt" panel will output at least 20 volts open circuit in daylight. BUT bare in mind, that it isn't voltage that charges a battery, it's current in amps, which require voltage to force those amps through the battery to do the charging. More light = more current. You can have in an open circuit, full or almost full voltage at the PV terminals, even on a heavy overcast dark day, but no useful current to do any charging.
    In other words, you need lots of light to produce the amps, and when you have the amps, the voltage will automatically be there.
    In the dark, the PV output will be 0 volts, and as the morning sky starts to brighten, the voltage will gradually come up, but no amps are available to charge until lots of light is striking the panels and by then the voltage has been up full for some time.
    Hope this helps.
    Cheers
    Wayne
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #3
    Re: Minimum voltage from a PV
    Wayne from NS Cana wrote: »
    as the morning sky starts to brighten, the voltage will gradually come up, but no amps are available to charge until lots of light is striking the panels and by then the voltage has been up full for some time.

    that is what I thought,;) it was just a fleeting question as we are always dealing with Vmp and Voc, but there is seldom mention of the opposite...
    Just that I have never seen what happens before the batt starts to get charged, the relay only clicks when my PVs put our more than the resting voltage AND .2 amps from the panels. CC uses .1, almost like an alarm clock except that it gets earlier and earlier.

    thanks,
    Eric
     
    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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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Minimum voltage from a PV

    Cool man :)
    All the best
    Wayne
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
    Re: Minimum voltage from a PV

    Eric,

    Every panel I have ever seen puts out 0.00 volts with no light,,,Going up from there with light! LOL.

    Tony

    PS Had 35cm of snow in the last 24! Temps still hovering about -3. Don't expect to see freezing until sometime later this week. At this rate we will have ice 'till June!
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Minimum voltage from a PV

    tony,
    i don't think you have long to wait as it's warming up nicely here in pittsburgh with things starting to green up so can you be far behind?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
    Re: Minimum voltage from a PV

    Another 12cm's this afternoon. 10 day forecast is colder than normal, but no more snow!

    I love it, my wife however is getting tired of it,

    T
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  • Telco
    Telco Solar Expert Posts: 201 ✭✭✭✭✭
    #8
    Re: Minimum voltage from a PV
    icarus wrote: »
    Another 12cm's this afternoon. 10 day forecast is colder than normal, but no more snow!

    I love it, my wife however is getting tired of it,

    T

    Need to hurry up and solve global warming then, before you guys up there freeze to death. I know I'm tired of the below average temps in the Oklahoma area, it's freakin' April and we are still having frost warnings at night and 50F degree days. We should be seeing 40-50F degree nights and 70-75F degree days by now.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #9
    Re: Minimum voltage from a PV

    Global warming is not everyone, every day has warmer temperatures. Its the average temperature is higher and the swings and extremes get larger and more frequent.

    For any one that pooh-poohs global warming, they should watch
    http://channel.nationalgeographic.com/channel/sixdegrees/

    1/4 of the world population water comes from glaciers ... and in about 15-20 years allot of those will have been melted, some thought it would be Melina’s, but with the rising global temperatures it much quicker

    You think we have problems now, wait when there is no water for India and surrounding countries.

    Related, in about the same time frame, the amazon will be gone, thanks to the use of BioFuels

    http://www.huffingtonpost.com/chris-mcgowan/biofuel-could-eat-brazil_b_64466.html
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #10
    Re: Minimum voltage from a PV

    I am a firm believer in human caused climate change, but I don't want to debate that here. We got another 15cm yesterday along with 75 km winds for lots of drifting. On the other hand it is bright sunny and my panels are putting out 130% of capacity this morning, with temps ~-10c and lots of reflection off the snow and lake ice. Hooray for MPPT!

    Tony
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  • System2
    System2 Posts: 6,290 admin
    #11
    Re: Minimum voltage from a PV

    Yeah, I too had awesome production on those winter days with the natural reflection off the snow adding to the sun. And the highest ever was during those days but with the sky having lots of super bright clouds as well, with the sun shining between them. So I had light from the sun direct; light from the clouds and light from the snow. Now the snow's gone and I really see the difference.
    Wayne
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