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diy solar

Epever settings for AGM & dropping voltage / low capacity. Help needed!

isolated

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Sep 2, 2022
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My setup: 3x250W panels, epever tracer 4215BN mppt controller (40A), 4x DC12-160 AGM batteries (connected in parallel), inverter connected to batter pack.
Location: at summer cabin, so mostly weekend warrior use.
Battery specs: cycle use 14.6-14.8V (25C), standby use 13.6-13.8V(25C)

Problem: when sun starts to shine, the controller begins to charge the battery pack as it should, up to 40A current but pretty soon (in 15-20 mins) the battery pack voltage rises to 14.8V and charge current drops to few amps, so one could assume that batteries are fully charged. But as soon as sun drops or there's any considerable load, voltage starts to drop quickly. After the sun sets, just few hours load of 5A will get the batteries near to disconnect limit (couple of times the epever controller actually cut off the load as voltage dropped so low).

Any ideas? Batteries are brand new, I tested them by disconnecting from the parallel connection and tested individually with controller, each giving the exact same voltage so apparently there are no faulty batteries and wiring between the batteries is working.

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Here are my settings

Temperature compensation coeff -3mv/C/2V
Over Voltage Disconnect Voltage 16
Charging Limit Voltage 15.0
Over Voltage Reconnect Voltage 15,0
Equalize Charging Voltage 14,8
Boost Charging Voltage 14,8
Float Charging Voltage 13,7
Boost Reconnect Charging Voltage 13,5
Low Voltage Reconnect Voltage 12,6
Under Voltage Warning Reconnect Voltage 12,2
Under Volt. Warning Volt 12,0
Low Volt. Disconnect Volt. 11,1
Discharging Limit Voltage 10,9
Equalize Duration (min.) 0
Boost Duration (min.) proper boost (aka absorb) 180
Battery type User
Battery AH. 640AH
 
You might have a bad SCC. It appears to be cutting out before charging your batteries up. This is not done in 15-20 minutes for a 640ah battery even with 40a charging current. Simple math for a 50% DOD would mean that 40a would take a minimum of ~8 hours to charge. (320ah/40a= 8h) and always longer since charging profile drops current as you near full charge. But it might not be because:

It is possible that all your batteries are now bad if the amount of solar power and SCC never was enough to get them recharged. I suggest getting a battery tester or load testing individual batteries. Voltage tests will not give you indication of depleted capacity.
 
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