Clipping

HotRodHotRod Registered Users Posts: 82 ✭✭
edited May 2019 in Grid Tie and Grid Interactive Systems #1
Hey guys! I have a question about why my system is clipping my array off at around 5kW? My array is 13.4kW. I have 2 6848's running in master/slave mode. I have 2 80-600 charge controllers. Shouldn't I be seeing close to the 9.8kW the charge controllers are restricted too? Or at least 80% of that.

Settings for the following images;
grid support enabled
grid support voltage was set to 64.1 as suggested in the manual
sell enabled

This was a clear sunny day. little haziness in the morning. No reason for those dips or the 5k clipping.
2 Schneider XW+ 6848 inverters
2 Schneider MPPT 80 600 Charge Controllers
Combox
40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • mcgivormcgivor Solar Expert Posts: 3,490 ✭✭✭✭✭
    #2
    What loads are there creating the sags, or what are the loads during the day?  Could it be the array is supporting loads, sometimes dipping into the battery thereby requiring some current to go towards the battery to maintain voltage setpoints? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #3
    PV output with load overlay
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #4
    I believe it was in the manual where I read that the equipment has a hard time distinguishing between reactive power and load power. Can the mysterious 2kW load that comes in right when the system starts clipping to 5kW actually be generated power?
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • mcgivormcgivor Solar Expert Posts: 3,490 ✭✭✭✭✭
    #5
    There are some significant loads, which it would appear the grid is supporting to some extent, what is the battery voltage in the critical 10:00 to 12:00  area ?
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #6
    the battery, same day
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • Dave AngeliniDave Angelini Solar Expert Posts: 5,422 ✭✭✭✭✭
    #7
    Who installed this please? Where/what manual does it say 64.1V in the manual?
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    edited May 2019 #8
    Dave Angelini, I installed the equipment.

    Conext XW+ Inverter/Charger Oweners Guide, Page 3-30, 1st paragraph, last sentence.

    Edit: Not sure if it matters but that manual is 975-0240-01-01 Revision G, April 2016
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    #9
    It's likely not directly related to your issue, but... 
    Charge controller capacities are rated by output current (80a in your case?), not wattage.  At 54v, 2x80a controllers might output ~8.6kw, less derating for ambient heat, altitude, restricted airflow, etc.  At nominal bank voltage, it would be ~7.6kw.  To get to 9.8kw, you'd need to be at absorb voltage on a pretty cold (near freezing) bank. 

    There's often a maximun array size restriction, which limits the degree to which the controller can be "overpanelled".  Overpanelling can be beneficial on light overcast days to still get useful power, but too much can be a problem, hence the restriction.  
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    edited May 2019 #10
    Estragon, thanks. Yes, I overpanelled specifically for overcast days. And it works nicely. I'm still covering all my nighttime usage on the most overcast days. I just worry about the dips in charging dictated by cloud coverage.

    If the equipment does have an issue distinguishing between load power and reactive power, then the mystery ~2kW load that shows up as the panels start producing is probably produced energy and that plus the ~5kW from the panels put me right around the 7-8kW output I was expecting the system to put out. 

    Equipment temp is heavily controlled. The equipment is inside the house, air-conditioned, and has yet to see room temps above 75°F at full tilt, sunny day, 88°F outside.

    -Jason
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • a1certifieda1certified Registered Users Posts: 34 ✭✭
    #11
    Curious about the sell voltage of 64.1V issue as well.  I have a 6048 system and arbitrarily set the sell voltage for 0.2V above float with the rudimentary understanding that a full bank "likes" to be at float voltage for their overall healthy and well-being.  So a sell voltage right above float (my battery manufacturer recommends 54.6V) seems to me to be simulating keeping the bank voltage near float and selling anything in excess.

    Two questions about setting the sell voltage significantly above float voltage:  
    1) Is it god for the batteries to be seeing such a high voltage for prolonged periods of time?
    2) Are you somehow decreasing the quantity of watts sold back to the grid by keeping the voltage that high?


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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #12
    1) Is it good for the batteries to be seeing such a high voltage for prolonged periods of time?
    My float voltage is still set at 54v as per the battery manufacturers specs. Here is what they recommended, and it's what I'm using in my inverter.
    Bulk= 59.4
    Absorb= 58.2
    Float= 54

    2) Are you somehow decreasing the quantity of watts sold back to the grid by keeping the voltage that high?
    Great question. One I can't wait to discuss with Schneider this afternoon. All I know at this point is that if I change no other settings other than GSV, The system Will produce ~9kW at 49.5v and ~5kW at 65v. I've only gotten it do put out 9kW once. All other times it stays between 7-8kW under same weather conditions.  Will report back when I know more.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • littleharbor2littleharbor2 Solar Expert Posts: 1,547 ✭✭✭✭
    #13
    Cold temps and cloud edge effect will give you highest output, for brief periods of time.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • a1certifieda1certified Registered Users Posts: 34 ✭✭
    #14
    HotRod,  

    My fear would be that the system is using all those watts to try to keep the battery bank at 65V and therefore limiting the amount available for selling back to the grid.  

    The thing that I wish were different about these systems is that all the PV goes "through" the batteries before going to its ultimate destination -- charging/absorbing, floating, loading, selling.  Wish there was a (smarter?) way of splitting the power before it got to the batteries.  Then the system could compute a charging power required to keep the system at float and then just send that amount to the batteries and send the rest to the inverter directly to either power loads or sell back to the grid.  

    The behavior that I've noticed with my system is that where there is ample PV input available, the PV charges the batteries as expected.  But when the bank gets "full" (i.e. at float voltage) all the power ends up "overcharging" the bank (my interpretation of seeing the voltage go to 4 volts above float voltage in a couple of seconds) followed by the system "overselling" the bank (my interpretation of seeing the voltage go to a volt or two lower than float voltage), followed by the cycle repeating itself over and over again, second by second thousands of times /day.  A picture below demonstrates this odd behavior.

    My settings are similar to yours.  Absorb 58.8, Bulk 58.8, Float 54.6, Sell 54.8


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  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    #15
    Power for loads and selling to grid doesn't really go "through" the batteries.  In float, ~ 1% of bank capacity will be used to keep  the bank at float voltage.  With no other loads, that's all the pv and charge controller will produce.  If there are added loads, pv will produce more, with that current going to the load, not the bank.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #16
    This is a pretty typical day for my batteries. The GSV was set t 65v around 5am. Y can clearly see where I dropped it back down to 49.5v around 630-7pm to the system back into keeping the battery as the primary power source. Never goes above the 57.6v programmed into the CCs.



    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #17
    My mysteriously perfect day. GSV set to 49.5v. I do not like that tug of war at the begining of the day before the battery went into float, where that stopped. From 9am til around 3 it just rocked. Then as the sun waned, it started tug of war with the grid and battery again. I'm learning, but I've not gotten it to do that again even on the clearest day with the same settings.


    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • a1certifieda1certified Registered Users Posts: 34 ✭✭
    #18
    Do you have graphs for Grid Input vs. Grid Output and Grid Input vs. Load Output on that same day?



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  • a1certifieda1certified Registered Users Posts: 34 ✭✭
    #19
    Your first graph seems to make sense to me.  See if this narrative rings true to you:

    System starts getting PV around 7AM.  System goes from resting voltage of 51.X V to absorb V of 57.X V.  Stays at absorb voltage for minimum absorb time (is it 90 minutes or so?) and then goes to float voltage of 54V until PV starts to wane around 5PM and then gradually fades to no PV input around 18:30-19:00 when we see the voltage drop back down to resting voltage of 51.X V.

    I'm glad to at least see you get the crazy see-saw/zig-zag that I can't figure out as well.  Although yours seems to be concentrated in the shoulder areas of the day (dawn and dusk) whereas mine seems to start after some sort of time interval which I assumed was the min absorb time, but upon closer examination might not be the case.
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #20
    No, that's a screen shot from May 20th. I still haven't picked up a memory card for the ComBox yet.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #21
    Wow. I just reread my comment. What a disaster. 

    "System starts getting PV around 7AM.  System goes from resting voltage of 51.X V to absorb V of 57.X V.  Stays at absorb voltage for minimum absorb time (is it 90 minutes or so?) and then goes to float voltage of 54V until PV starts to wane around 5PM and then gradually fades to no PV input around 18:30-19:00 when we see the voltage drop back down to resting voltage of 51.X V."

    I actually get up everyday at about 0430. Have a cup of coffee and raise the GSV to 65v so the equipment wont play push-pull with the battery-grid interface. As you can see in the graph, it pushes the voltage to 57.6 on a slow ramp during bulk and then maintains that voltage down to the 2% when it drops into float. If it's a cloudy day I don't mess with it again, but if it's sunny, I'll put the GSV back to 49.5v and watch the system push as much as ~6kW back at Kenergy. Now, if I do that, I really have to babysit the system. Any drop in PV output seems to make the system immediately want the battery, even when the PV is outputting more than load demands. I have seen it say it is producing ~6kW, putting 1.5kW to the loads while putting ~6kW on the grid and using 1.5kW from the battery to maintain the push on the grid. It's short lived, usually less than a minute, but taking the battery from float state to discharge and back to float state in 2 minutes just sounds bad.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #22
    Yesterdays plots. No sun all day.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #23
    How the battery performed, same day.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #24
    Grid, same day, same fashion as you posted.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • mcgivormcgivor Solar Expert Posts: 3,490 ✭✭✭✭✭
    #25
    @HotRod Just a thought but perhaps a battery monitor would provide more accurate measure of its actual battery performance, yeah I know, another device and $$ 

    My system shows the battery being charged at night, the wattage is reflective of the inverter self consumption, so it would seem since it has no shunt to provide accurate data of what goes in and out of the battery, it assumes the inverter's self consumption is charging. When actual loads turn on, the refrigerator for example it appears accurate, but returns to apparent charging once off.

    Currently in just getting into the Combox monitoring, lots of unanswered questions, perseverance will prevail, only wish tech support was more forthcoming and responsive, but it is what it is, I guess.
     



    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    edited May 2019 #26
    This is a good example of the mystery load following the grid output. I'm beginning to think it heat losses in the equipment. It sure isn't load in the house. Repeatedly verified with amp clamps, 3 to be exact, all fluke, all in agreement.

    I'm flirting with the battery monitor. I bought a cheap one from amazon. Its a direct line shunt so I should be able to get some usable info from it, hopefully. As I said, it was cheap so...

    Lots on my plate right now, so I'mma have to back burner this until I get caught up. Maybe in the next week or two I can get the shunt installed and the temp sensor for the CCs.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #27
    I just came across this. Haven't read it yet but, here it is.

    http://www.xantrex.com/documents/Accessories/Combox/975-0704-01-01_RevA(Vendor).pdf
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • mcgivormcgivor Solar Expert Posts: 3,490 ✭✭✭✭✭
    #28
    HotRod said:
    I just came across this. Haven't read it yet but, here it is.

    http://www.xantrex.com/documents/Accessories/Combox/975-0704-01-01_RevA(Vendor).pdf
    That's an earlier revision of the Combox manual that is available on the Schneider website, RevE
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • BB.BB. Super Moderators, Administrators Posts: 30,952 admin
    #29
    Latest Combox Installation Manual I could find "975-0679-01-01 Rev F" (copyright 2015):

    https://www.wholesalesolar.com/cms/schneider-conext-combox-installation-manual-3402706265.2430067.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #30
    I haven't done this much research since I was part of the Army's DPGDS program. The DPGDS was the military's first diesel prime mover with digital controls. We were working with the designers to shake out problems on the fly in the field. I deployed with those units to Iraq in '03 and destructive testing wasn't even conducted (also by us) until 2005. It was learn as you go. This feels a lot like that. 
    My current favorite reading material:
    https://41j5tc3akbrn3uezx5av0jj1bgm-wpengine.netdna-ssl.com/wp-content/uploads/2016/07/Conext-XW-Multi-Unit-Power-System-Design-Guide-975-0739-01-01_Rev-C_ENG.pdf
    https://41j5tc3akbrn3uezx5av0jj1bgm-wpengine.netdna-ssl.com/wp-content/uploads/2018/05/MN20180201_Conext-AC-Coupling-Solutions-Guide-976-0240-01-01_Rev-E_ENG.pdf
    I'm starting to really get my warm and fuzzy on the equipment now. I'll get there, I'm just slow.

    mcgivor, BB, many thanks. Y'all both provide a mountain of good posts in here. Many kudos for all the sharing.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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  • HotRodHotRod Registered Users Posts: 82 ✭✭
    #31
    I feel like I still have a lot of learning to do and I'm sure there's tons of room left for improvement, but here's what I'm looking like right now.

    Battery, same day.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
    · Share on Twitter
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