Connecting series PV panels

Arkansasoffgrid
Arkansasoffgrid Solar Expert Posts: 117 ✭✭
in Solar Beginners Corner #1
When making the series connections of 3 panels, should the panels be "covered" so no power is being generated during the string connecting?
8-420AH US Battery L-16s, Midnite Classic 150cc, Whiz Bang Jr, Magnum MS4448PAE inverter/charger,  4590w Canadian Solar panels. Honda EU2000i generator.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Connecting series PV panels

    Panels are a current source: without a circuit they produce no power. You can plug them together without worry of arc or spark so long as there is no load connected to the output.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #3
    Re: Connecting series PV panels

    Two issues...

    1) you don't want to get shocked. Three panels in series is pretty close to 120 VAC shock--And DC shocks can be worse. If you are comfortable working on "hot 120 VAC connections", you can make these up too (use insulated tools, don't work with two hands--one on wire, second grounded to metal framework, etc.). Make sure that any electrical boxes/equipment are properly grounded before making up hot connections.

    2) current flow... Making up the MC 4 connectors, you do not want current flow. Making sure the DC disconnect/breaker is off (if you have one) and or making up a non-MC4 connection last will reduce arcing and prevent damage to the MC4 connectors.

    Many years ago, folks who worked with electrical circuits were pretty cavalier working with low(er) voltages.

    Today, there have been enough people that have been injured or even died hours/day or so later after getting hit with 120/240 VAC--That the doctors and regulatory agencies are much more careful and preventing any shocks in the first place and even mandating trips to the ER after "minor" shocks.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #4
    Re: Connecting series PV panels

    What i did was tape all the mc4s male and female pairs together but not connected. Route the pv cables tie them down neatly and terminate at the combiner. PV breaker off as said above. When ready to make live, clip the mc4s, one string at a time. Then check voltage and polarity at combiner. Finally, when your happy flip the breaker on (makign sure that the controller is also first on). Done slowly and mindfully, its a safe enough procedure, but best have someone nearby just in case. Same as working with batterys, or chainsaws...

    And for those that try and get away without a combiner (like i did inittally), you have a related problem. How to service the disconnect, with no way to depower the array outside? Combiners are good for that...among other things.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Connecting series PV panels

    You can power down an array by covering it.
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  • Arkansasoffgrid
    Arkansasoffgrid Solar Expert Posts: 117 ✭✭
    #6
    Re: Connecting series PV panels

    Thanks, that seems like the safest way for me.
    8-420AH US Battery L-16s, Midnite Classic 150cc, Whiz Bang Jr, Magnum MS4448PAE inverter/charger,  4590w Canadian Solar panels. Honda EU2000i generator.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #7
    Re: Connecting series PV panels

    Remember that even a little amount of light leaking through a "less than black" blanket/tarp can still energize a panel with enough current to shock (0.001 amps) or kill (0.015 to 0.100+ amps).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #8
    Re: Connecting series PV panels
    BB. wrote: »
    Remember that even a little amount of light leaking through a "less than black" blanket/tarp can still energize a panel with enough current to shock (0.001 amps) or kill (0.015 to 0.100+ amps).

    -Bill

    Funny, at night down here in FL when it is a clear sky and a full moon, my PV voltage sometimes shows around 13-14v (my pv runs at 101 voc). Not enough amps (if any) to bring the controller out of silent/sleep mode but just interesting that even reflected sunlight off of the moon could produce a tiny bit of voltage.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Connecting series PV panels
    jcheil wrote: »
    Funny, at night down here in FL when it is a clear sky and a full moon, my PV voltage sometimes shows around 13-14v (my pv runs at 101 voc). Not enough amps (if any) to bring the controller out of silent/sleep mode but just interesting that even reflected sunlight off of the moon could produce a tiny bit of voltage.

    When I had three in series on the 12 Volt system the MX60 would wake up under a full moon and try to start, but of course there was never enough current for it to stay active. This is the difference between the relative ease of achieving Voc (and thus > last V triggering a start attempt) and actually producing power.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #10
    Re: Connecting series PV panels
    jcheil wrote: »
    ... just interesting that even reflected sunlight off of the moon could produce a tiny bit of voltage.
    Of course what is really happening is that the light is producing full voltage but at low current and the internal leakage resistance of the cells is dropping the output voltage down below what we are used to seeing as Voc.
    SMA SB 3000, old BP panels.
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