Re: AGM batteries - voltage falling
after 20 hours of charging with 60A charger you have 80% charged batteries? I would say that this is not ok. I have 11 years old Victron batteries that charge to 100% in less than that time . Have you recorded the charging current? What was the value after 20 hours? I bet that it was very low. Voltage of 22,3V @-3,1A is bad. This 11,15V per 12V battery. I would say this is 30% charged batterie.
What kind of test was done by Mastervolt technician? Did he disconnect all the batteries?
I would measure voltage on all batteries when you have 20V. If all of them are at 10V then you need a new batteries. To have a correct test of batteries one have to measure every battery separately. Open Circuit Voltage of 11,5V is close to 30% I would say.
I have 380Ah batterie bank and I am now connected to shore power in marina. I have 400W of solar I installed and 150W are removable. So together 550W. Few days ago I tested the system, disconnection the shore power. Fridge, freezer were on, I cooked on Induction. I performed test like being on anchor. After 2,5 days I had 24,5V. When induction was running it dropped to 23V but then returned to previous value. I never went bellow 75% charge of the bank during the test.
I hope this helps.
#279 Bonne Anse in Croatia