FM80 equalization voltage

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706jim
706jim Solar Expert Posts: 514 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Two recent attempts at equalization using my FM80 were interesting. Equalization voltage was set at 31.0 but the batteries reached 30.2 volts no more. And yes, there was adequate solar, both amperage and time to perform the equalization. Previously this season the voltage reached the programmed 31.0 during equalization.

I tried changing the equalization voltage to 31.8 but charging once again stopped at 30.2 volts.

Otherwise all of the other functions work as expected. My battery bank is 8 L16's in series parallel 740A-hr capacity.

Bulk 29.8 float 27.6 volts. I've checked battery voltage carefully and it agrees with the Outback voltage display.

I thought of doing a system reset but was reluctant to try this as I will be away from the location for the next six months.

Any suggestions?
Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #2
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    Is your array setup? is it setup to provide 130-150% of 31.8 volt VMP?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • 706jim
    706jim Solar Expert Posts: 514 ✭✭✭✭
    #3
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    Photowhit said:
    Is your array setup? is it setup to provide 130-150% of 31.8 volt VMP?
    Yes array will reach about 44 volts when the load goes to zero.
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #4
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    706..,

    To expand on Photowhit's question,  during that EQ,  what was/is,  the Vin to the FM (the PV input voltage to the CC)?  What is the difference twix the PV in,  and the battery voltage?

    And am certain,  that the batteries were fully-charged,  before starting the EQ (?).

    It can require a LOT of current to reach the EQ voltage on FLA banks,  which really need the EQ.

    Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • 706jim
    706jim Solar Expert Posts: 514 ✭✭✭✭
    #5
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    There was definitely enough overhead voltage and current to perform the equalization. It's just that the FM tapered off the current so as to maintain the 30.2 volts I mentioned. Batteries were at float 27.6 when I started the EQ. Something in the FM I just don't know exactly what.
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited November 2021 #6
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    OK,  but,  "definitely enough overhead voltage,  and current",  is not that satisfying.

    IF: the FM-80 can temp compensate the EQ voltage,  and,  if, that was enabled on it,  and, the Trojan batts have a charge compensation coefficient of 0.05 mV/cell/degree C,  AND the batteries were HOT (about 13 degrees C above the probable Reference temp of about 25 C),  then,  this could explain what you seem to be seeing  ... that would be about 100 degrees F,  the way that I look at it.

    Good Luck !!   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #7
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    706jim said:
    Photowhit said:
    Is your array setup? is it setup to provide 130-150% of 31.8 volt VMP?
    Yes array will reach about 44 volts when the load goes to zero.
    Please understand that if 44 volts represents the VOC, or no load voltage. that will NOT be high enough for the charge controller to work properly on a 24 volt system.

    Understand that boB and Robin Gudgel who built the FM80 before opening and building the Midnite classic, recommend a VMP (under load) to be 30% higher than the voltage being exported from the charge controller. 44 volts VMP tends to be 80% of VOC or 44x.8= 35.2 volts.

    At the bottom of the Midnite classic array sizing tool, is this information; 
    Heat also effects the voltage output of solar panels, along with wire drop of DC wiring which can be pretty high when running a long distance, and hard to detect when measuring minor voltage across a DMM.

    Anywho, that's all I was trying to get across, temperature compensating charge voltage would be my next area of discussion.
    Wish I knew more about the FM80. 



    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • 706jim
    706jim Solar Expert Posts: 514 ✭✭✭✭
    #8
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    I will investigate the performance of the system when I'm back next year and the temperature is warmer. There was no problem reaching my 31.0 volt equalization voltage when I did this operation in the summer months. This recent anomaly occurred with battery temperatures at my season's end of around 40-45F, definitely not hot. And panel voltage if anything is higher when the temperature drops. While I never mentioned it, charging current in full sun runs from 40-50 amps occasionally as high as 70 amps.
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    edited November 2021 #9
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    This is not likely the issue, BUT, there should still be a menu item that limits the maximum temperature compensated voltage limits.


    This would be maximum and minimum charge voltage limits and was originally intended for GEL and AGM batteries.

    The EQ may not be temp-compensated but you might look at that menu jut in case.   It has been many years and the last engineer on the MX/FM CCs  may have changed the way that part works.

    AND somewhere in the MISC menu, if still there, should be a "target" voltage at which the FM is trying to get the battery to, temp compensated or not.     Might be worth a look.

    boB




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  • 706jim
    706jim Solar Expert Posts: 514 ✭✭✭✭
    #10
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    Thanks Bob. I will check that when I get to see the system next time. That will be at least three months from now.
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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