Stuck in bulk charge

fredb
fredb Registered Users Posts: 11 ✭✭
7 strings of 3 260 watt panels.
48 volt system
dual inverters and charge controllers
2 strings of 8 batteries (6 v per battery)

Yesterday about 5:00 PM I checked the meters. One charge controller (CC) was in float mode as it should be after a long sunny day and the other was in bulk.At the time the output voltage was not 58 volts which is the bulk charge voltage so that was good. I checked the battery specific gravity after an hour of disconnect and they were indeed at full charge. I am concerned that at times the batteries are getting overcharged due to one CC staying in Bulk mode. At times I am sure I have seen the charge voltage at 58 even when the batteries were already charged for the day. Anyone know why it wold stay in bulk mode?


Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Do you have them  connected inn "follow me"
    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.
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited August 2019 #3
    The thing I'm curious about is if the controller in the left pictures is in float, why is it still passing 29.1A to the battery, > than the one in bulk? Has there been a rebulk voltage programmed and what you are seeing is a delayed reaction in the left controller transitioning to bulk because the battery voltage is below what float would normally be FLA, 54V. Normally a rebulk voltage would be set at~ 50V, being near the end of day perhaps this is what's happening.

    Not being a Midnight user this is merely a hypothetical observation, based  on experience with other equipment.

    Edit: Are the controllers on seperate arrays? that would be my assumption but you never know, if sharing with MPPT controllers all kinds of weird things could happen.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    mcgivor said:
     "...if the controller in the left pictures is in float, why is it still passing 29.1A to the battery..."
    It's not passing it to "the battery" but to the system. Likely has some air conditioners running!

    I do find  it interesting that the 'bulk' CC is contributing less, but has contributed more to the system during the day.

    The difference in the system  voltage does bother me a little bit, And the low system voltage is interesting, wonder the  time of day this is going on,  but 15 kWhs in and  producing 2.5 kWs it's likely late in the day. Before I setup "follow me", even with the same settings my charge controllers would often be at different states of charge.
    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.
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited August 2019 #5
    Photowhit said:
    mcgivor said:
     "...if the controller in the left pictures is in float, why is it still passing 29.1A to the battery..."
    It's not passing it to "the battery" but to the system. Likely has some air conditioners running!

    I do find  it interesting that the 'bulk' CC is contributing less, but has contributed more to the system during the day.

    The difference in the system  voltage does bother me a little bit, And the low system voltage is interesting, wonder the  time of day this is going on,  but 15 kWhs in and  producing 2.5 kWs it's likely late in the day. Before I setup "follow me", even with the same settings my charge controllers would often be at different states of charge.


    The time was 5 PM, the inverter  load of 11.6A is, I'm assuming,  taken at near the same time to provide a graphical example, so yes some unanswered questions. You are correct some current would be going to loads and not necessarily all to the battery itself.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • fredb
    fredb Registered Users Posts: 11 ✭✭
    Thanks for the comments! I checked my settings again and neither CC is set to rebulk. (Rebulk is set to 8v). They are not set to follow me either. I did find that somehow I had entered 3 minutes instead of 3 hours for absorb time on the left CC. Apparently, it was basically skipping absorb and going to float. The sudden drop in amperage from the one CC must have made it possible for the other to go back in to bulk mode for a while. I am going to do some more testing to make sure that was the issue.