Solar Charging Seasons

stmar · November 2018

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?

Estragon · November 2018

Are the batteries in a cold location?

Is there a remote temp sensor attached to the batteries?

stmar · November 2018

BTS attached, right now showing in the low 60's.

mcgivor · November 2018

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?

stmar · November 2018

Yes, normal various household loads. Charge controller is a Morningstar PS30 PWM controller.

AGB · November 2018

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.

stmar · November 2018

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.

Solar Charging Seasons

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