voltage drop at same time each night

[sirmoiu]

Hi I am having a problem with my battery bank each morning around 5am, one of my battery voltage would drop under load, it would drop to about 11.9 while the other 3 batteries would remain around 12.4, my system is 48 volts, 4 200 amps hr. Gel batteries, when I switch to city power all the batteries would rest at 12.6 including the one that had the voltage drop. It is the same battery each time, do I need to take that battery out of the bank.

[Westbranch]

It certainly sounds like it is failing. 
How old are they?
Can you charge it separately, disconnect it   and observe it after 3 hrs or more under no load and then under load?

[sirmoiu]

They are a little over 2 years old, yes I can charge it separately, ok, I will check it under load and without any load. thanks

[sirmoiu]

Hi, ok I think I found the problem, I will continue to do more testing to be sure, I suspect it is my midnite solar charger 12v relay turning on in every morning around 5 am, you see I have a small computer fan connected to my aux 1 relay and I would put it on auto and leave it, I think the 12v relay would come on, so now each night I will shut it off, this is my second night I will let you know what happens. Thanks.

[BobWhite]

Hi, ok I think I found the problem, I will continue to do more testing to be sure, I suspect it is my midnite solar charger 12v relay turning on in every morning around 5 am, you see I have a small computer fan connected to my aux 1 relay and I would put it on auto and leave it, I think the 12v relay would come on, so now each night I will shut it off, this is my second night I will let you know what happens. Thanks.

Hi, You have the fan wired to the (one) battery for 12 volts from a 48 volt bank or are you wired to the aux 1 on the classic to provide the 12 volts to run the fan?