Solar Charging Seasons

stmarstmar Solar Expert Posts: 323 ✭✭✭
My Conext SW4024 is acting differently as the seasons change so I would like to get some opinions as to if it is normal. In my part of the country we have 4 - 5 hours less solar now (Fall/Winter) on a normal day than we had in the Summer. During the day my AGM battery bank charged by solar array is showing high 28's voltage, normal for all seasons. When the sun goes down the voltage drops to the mid to high 25's, same all seasons. During the Summer the SW4024 would rarely go into the charge cycle but now it seems to cycle more. It seems the batteries are not getting enough charge during the day and the load of the Sunfrost RF-16 is dropping the voltage to 25 volt set point to trigger charging at night. When this happens the SCP shows Bulk for about 10 minutes then Absorption for 10 or 20 minutes then Float for a few minutes then AC Support until it drops to 26 volts then AC In Good where it stays until it hits the 25 volts and the cycle repeats. The time between the 26 dropping to 25 is variable depending on how much the RF-16 runs, the two compressors on it pull 7.5 amps each on start up.
Why would the charge cycle; Bulk, Absorption, Float, be so short if the batteries need charging?

Comments

  • EstragonEstragon Registered Users Posts: 3,581 ✭✭✭✭✭
    Are the batteries in a cold location?

    Is there a remote temp sensor attached to the batteries?
    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
  • stmarstmar Solar Expert Posts: 323 ✭✭✭
    BTS attached, right now showing in the low 60's.
  • mcgivormcgivor Solar Expert Posts: 2,811 ✭✭✭✭✭
    What charge controller are you using? With the Conext 60-150 you could look into history and see if there is a downward trend in production or an abrupt change. Your  25V setting may be on the high side thus never actually using much of the battery capacity because grid is constantly making up the used capacity, resulting in low PV input. Are there loads during the day? 
    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.
  • stmarstmar Solar Expert Posts: 323 ✭✭✭
    Yes, normal various household loads. Charge controller is a Morningstar PS30 PWM controller.
  • AGBAGB Registered Users Posts: 24 ✭✭
    stmar said:
    My Conext SW4024 is acting differently as the seasons change so I would like to get some opinions as to if it is normal. In my part of the country we have 4 - 5 hours less solar now (Fall/Winter) on a normal day than we had in the Summer. During the day my AGM battery bank charged by solar array is showing high 28's voltage, normal for all seasons. When the sun goes down the voltage drops to the mid to high 25's, same all seasons. During the Summer the SW4024 would rarely go into the charge cycle but now it seems to cycle more. It seems the batteries are not getting enough charge during the day and the load of the Sunfrost RF-16 is dropping the voltage to 25 volt set point to trigger charging at night. When this happens the SCP shows Bulk for about 10 minutes then Absorption for 10 or 20 minutes then Float for a few minutes then AC Support until it drops to 26 volts then AC In Good where it stays until it hits the 25 volts and the cycle repeats. The time between the 26 dropping to 25 is variable depending on how much the RF-16 runs, the two compressors on it pull 7.5 amps each on start up.
    Why would the charge cycle; Bulk, Absorption, Float, be so short if the batteries need charging?
    Any time you start charging, it starts from bulk - absorption - float no mater the voltage.  That might be why you are seeing the cycle when your load pull the battery voltage low. 
    You can change the charge trigger on the inverter to a lower voltage than what it is now and see.
  • stmarstmar Solar Expert Posts: 323 ✭✭✭
    I thought 25 volts was low, what voltage do others use for a 24 volt system? I am going to do some testing this week and see if I can determine the health of the battery bank. I can't figure out why the cycle, bulk absorbtion float, is so short when I have absorbtion set at 3 hours.
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