? wiring 3 panels in parallel

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lipets
lipets Solar Expert Posts: 61 ✭✭
in Off Grid Solar & Battery Systems #1
I wired 3 panels in parallel, each panel was putting out 6.8 amps and 65 volts.


I ran all 3 positives to a combiner buss bar, and all 3 negatives to another.



When I checked the combiner connections with all 3, the output across the two buss was the same?



Shouldn't the amp readings be higher like triple (20 amps)?



did I wire something wrong?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: ? wiring 3 panels in parallel

    Nope; it sounds like you wired it right. All negatives to one bar, all positives to the other.

    Now, how did you read the current? The combined current would be > 20 Isc which would fry most DMM's.

    Now if you accidentally put one panel in backwards it would negate the current from another and you'd be left with roughly the current of the one remaining panel.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #3
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    Re: ? wiring 3 panels in parallel

    What is the make/model of panels?

    68 volts Vmp or Imp is pretty high for most panels (and makes this something 400 watt panels, each).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • lipets
    lipets Solar Expert Posts: 61 ✭✭
    #4
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    Re: ? wiring 3 panels in parallel

    they are Kerocera ba 195, the voltage is correct.

    Without removing the panels how can I double check the polarity?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: ? wiring 3 panels in parallel
    lipets wrote: »
    they are Kerocera ba 195, the voltage is correct.

    Possibly Kyocera? I know they make a 190 Watt. It would be 26 Vmp and about 7 Imp.

    But as per Bill's math and your original post 6.8 Amps * 65 Volts is 442 Watts. This doesn't make sense.
    Without removing the panels how can I double check the polarity?

    Panels have to be disconnected from at least one bus bar to check polarity.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #6
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    Re: ? wiring 3 panels in parallel
    lipets wrote: »
    I wired 3 panels in parallel, each panel was putting out 6.8 amps and 65 volts.


    I ran all 3 positives to a combiner buss bar, and all 3 negatives to another.



    When I checked the combiner connections with all 3, the output across the two buss was the same?



    Shouldn't the amp readings be higher like triple (20 amps)?



    did I wire something wrong?
    The amp readings will only be higher if you short out the panel output to measure it or the CC and battery are in a position to actually use that additional current.

    Did you measure 6.8A and 65V at the same time, giving you Imp and Vmp with an MPPT type CC and the CC in Bulk mode.
    If you are using a peak catching or even averaging DC meter and the CC is using PWM on the input side (even an MPPT CC might do that if the batteries are not in Bulk) then the voltage you measure will be somewhere between Voc and (Voc - (Voc-Vmp)/2). That could explain [part of] (Thanks Coot.)
    why the product of current and voltage is higher than nominal panel power.
    Another source of error could be that your voltmeter is just messed up. :)
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: ? wiring 3 panels in parallel
    inetdog wrote: »
    The amp readings will only be higher if you short out the panel output to measure it or the CC and battery are in a position to actually use that additional current.

    Did you measure 6.8A and 65V at the same time, giving you Imp and Vmp with an MPPT type CC and the CC in Bulk mode.
    If you are using a peak catching or even averaging DC meter and the CC is using PWM on the input side (even an MPPT CC might do that if the batteries are not in Bulk) then the voltage you measure will be somewhere between Voc and (Voc - (Voc-Vmp)/2). That could explain why the product of current and voltage is higher than nominal panel power.

    It would not explain a Voc of 65 on a panel set that probably has a Voc around 32. The alternating between loaded and unloaded panels will only produce a V between Vmp and Voc: not 2X expected.
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  • lipets
    lipets Solar Expert Posts: 61 ✭✭
    #8
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    Re: ? wiring 3 panels in parallel

    I was taking the readings unloaded without anything attached, no controller no batteries.

    Waiting for the controller to be delivered in few days.

    The panels are 195 watts
    Voc 68.1

    I was rounding it off to 65 for simplicity of the question.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: ? wiring 3 panels in parallel
    lipets wrote: »
    I was taking the readings unloaded without anything attached, no controller no batteries.

    Waiting for the controller to be delivered in few days.

    The panels are 195 watts
    Voc 68.1

    I was rounding it off to 65 for simplicity of the question.

    In that case we can expect the Vmp to be around 55 and the Imp around 3.5, not 6.8.
    55 * 6.8 = 374 Watts whereas 55 * 3.5 = 192 Watts. Isc will be somewhat higher. Perhaps 4 Amps, but certainly not over 6.

    All three panels in series to a dead short should read 3X Isc or in the neighborhood of 12 Amps. If you don't have a DMM that can read 20 Amps on its leads do not try to read the Isc of all three panels at once.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #10
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    Re: ? wiring 3 panels in parallel

    Suggestion:
    If you are going to be working with PV a lot, invest $50 or so and get a clamp type DC ammeter.
    SMA SB 3000, old BP panels.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #11
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    Re: ? wiring 3 panels in parallel
    lipets wrote: »
    I wired 3 panels in parallel, each panel was putting out 6.8 amps
    inetdog wrote: »
    Did you measure 6.8A and 65V at the same time
    lipets wrote: »
    I was taking the readings unloaded without anything attached

    lipets, you can't possibly measure a current (other than zero) from an unloaded panel. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • lipets
    lipets Solar Expert Posts: 61 ✭✭
    #12
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    Re: ? wiring 3 panels in parallel
    vtmaps wrote: »
    lipets, you can't possibly measure a current (other than zero) from an unloaded panel. --vtMaps

    thanks, so my reading om amps is incorrect.

    Need to get the clamp type meter, under load.
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