System Test Day in T-24 hours.. Guess the wattage..

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ywhic
ywhic Solar Expert Posts: 621 ✭✭
in Off Grid Solar & Battery Systems #1
Well I have 1 panel on my 25 degree angle mount.. (my location here (NJ) calls for for 36 spring and 12-16 for summer..) I'm in between at 25 degrees..

The panel is a 145w DMSolar..

Specs are:

VMP 18
IMP 8.05
VOC 21.6
ISC 8.95

Morningstar TS-45 (PWM) controller.. TS meter..
Combiner Box (QO Breaker Type) (with 2 1/2 Feet of 6AWG to the controller).. 5 feet of 6 AWG wire to battery.

a single 10' of 10AWG PV wire that will be cut in half for the testing (5' leads)..

PICT0025.JPG

25DegAngle.jpg

Today I got 20.6 VOC at 1:30 (83 F outside)..

Anyone like to guess the wattage and volts to the controller for tommorrow at 1:30pm facing SOUTH (like the above picture)??
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #2
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    You might need to move the fence a bit farther from the front of the array... Winter/morning/afternoon may cast shadows (keep shadows to zero if at all possible during ~9a-3p at least).

    Note the Voc is not very useful... Set up a test fixture (switch+hunk of wire) for a dead short... More or less 1,000 w/m2 ~ Isc.

    And:
    • (Imeasured-sc/Isc-rated) ~ fraction of full sun.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #3
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    Thanks... I will back up the panel away from the fence tommorrow.. (fence doesn't move, the panel does)..

    I don't know what you mean by dead short??? Not worried about a test fixture as I have the actual components..

    Tommorrow I will have the panel wired with 5' of wire to the combiner and then the charge controller and meter then to the 12v battery.. I should be able to get some usable data..

    I can't do the inverter part of the test as I don't have any yet.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #4
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    The "test fixture" I was suggesting was a pair of MCx connectors, a switch, and a length of wire. You can "dead short" solar panels, but you really should not do it without a switch. Plugging/unplugging and DC wire with current flowing (typically >12 VDC) can create sustainable arcs--which in this case--could damage your MCx connectors (hence the switch).

    If the array output is less than ~10 amps, most DMM's will measure DC current directly (connect your MCx wiring to the DMM directly). For more than 10-20 amps, you should use a DC current clamp meter.

    But--you really do not need to do this testing (other than as a one off/diagnostic test)--I was just suggesting Imeasured-sc as a better representation of what is happening with your panel vs Voc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #5
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    Ok.. thank you.. I've been making lots of notes since joining the forums.. you folks have really helped..
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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #6
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    Ok.. after much mumbling..

    Came up with about 110 watts from the 145w panel.. I had no load.. just the battery charging.

    Numbers started at 83w and 5.8a and then slowly went up as the 2 hours of testing progressed..

    Got a high of 111w and 7.4 amps in PWM... (my panels were at 25 deg angle and should have been at 12 degree for my location)

    Ended up in Bulk at 112w and 7.6a.. Also said 16.2 AH accumulated.. Thanks to Cariboocoot and BB for the numbers explanations..

    PICT0027.JPG

    Cloudy at 11:30 am..
    PICT0030.JPG

    Solar panel voltage then.. (was about 80' F).
    PICT0031.JPG

    [video=youtube_share;KelMmC8xOnA]http://youtu.be/KelMmC8xOnA[/video]
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    For people who like math:

    112 Watts * 100 / 145 Watt STC rating = 77% efficiency!

    Anybody surprised? :D
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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #8
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    Monday or Tuesday (if not sooner).. I will be adjusting the angle down to 12-16 degrees for my 40.XXX lat here in NJ..

    Maybe the numbers will go up abit.. but I am happy with the 110-112w per panel (glad I got 5).. :cool:

    Got my Killawatt meter in today.. so I can play with that now..
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    al,
    solar noon on the summer solstice would be lat -23.5 degrees. this would be the highest the sun will be in the sky so for all other times of day or the time of the year the sun will be lower in the sky meaning a higher pv angle.

    40-23.5=16.5 degrees at solar noon summer solstice. going with a smaller angle than this will not get you more power and may even start subtracting a tad of power.
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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #10
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    Re: System Test Day in T-24 hours.. Guess the wattage..
    niel wrote: »
    al,
    solar noon on the summer solstice would be lat -23.5 degrees. this would be the highest the sun will be in the sky so for all other times of day or the time of the year the sun will be lower in the sky meaning a higher pv angle.

    40-23.5=16.5 degrees at solar noon summer solstice. going with a smaller angle than this will not get you more power and may even start subtracting a tad of power.
    Monday or Tuesday (if not sooner).. I will be adjusting the angle down to 12-16 degrees for my 40.XXX lat here in NJ..

    Maybe the numbers will go up abit.. but I am happy with the 110-112w per panel (glad I got 5)..

    Got my Killawatt meter in today.. so I can play with that now..

    Correct.. I read 12 on macslab and then 16 on macslab based on 2 or 4 panel tilts a year..

    I'll do like a 16 angle then.. I just want to get as much as I can from the panel in my silly testing..

    My numbers for when in TX (30.69 lat) from macslab are:

    Summer 3.93
    Autumn 27.77
    Winter 51.31
    Spring 27.77

    Probably just either do 7 for summer and 45 for winter (macslab says 7.54 and 46.05).. or just set at 25 degree for year round (macslab says 26.42 for year round)..
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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #11
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    Does anyone think hooking a 2nd panel to it would be good to see the numbers??

    I would fathom it would be the same voltage but higher AMPS (or AH) getting fed into the battery..

    I could drag a 2nd panel from my storage down the road and do a 2nd test on Wed/Thursday..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
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    Re: System Test Day in T-24 hours.. Guess the wattage..
    ywhic wrote: »
    Does anyone think hooking a 2nd panel to it would be good to see the numbers??

    I would fathom it would be the same voltage but higher AMPS (or AH) getting fed into the battery..

    I could drag a 2nd panel from my storage down the road and do a 2nd test on Wed/Thursday..

    Parallel panels and that's what you get: same Voltage, higher Amps. You will also see less time at Bulk & Absorb for the same SOC recovery as the higher current will recharge faster.
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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #13
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    Anyone got a suggestion for a 12v load I can put onto the battery.. so I can make this thing cycle abit??

    I'm thinking a bulb on a socket maybe??

    I won't have my inverter for 3 weeks as I am saving for the SW 2000 Xantrex..
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  • Generic
    Generic Registered Users Posts: 27 ✭
    #14
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    Re: System Test Day in T-24 hours.. Guess the wattage..

    Leaving your battery at near full capacity won't hurt it. But if you want something to do with it maybe you could use a 12v fan. I use mine every night while I sleep. It uses 1.1 to 1.8 amps depending on the speed. Cost me about $50 but it's probably run 3000 hrs so far and still going strong.
    I also like the math. That's only about 1.7 cents an hour if it stopped working right now.
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