Hello John,

I gather from your post that the AGMs performed this way
from the outset (i.e., when they were new).

New AGMs at 50% state of charge should measure something
like 12.5 volts.

A new, fully-charged AGM bank of 420 AH under a 5 ampere
load should see virtually no voltage drop from the 12.7 volt
nominal no-load voltage.

If the bank is 50% charged and you are drawing 60 amperes,
the voltage may drop to something like 11.7 volts under load.

As the Ocean Navigator article suggests, failure to charge
to 100% could result in degradation of performance. However,
this would not have been noticeable when the batteries were new.

Hope this info helps.

Chuck


wrote:
I have 2 4D Lifeline batteries. I bought them new last Augaust before
we left for Mexico. We have been having a great time but the batteries
are not doing nearly as well as advertised. They are in one bank of 420
amps for the house bank and I use it for everything including starting
the engine and leave another battery charged for emergency starting. We
use about 60 amps a day. I have been discharging to between 80 and 100
amps then charge back to between 20 to 40, depending on how long we
want to hear the motor running. I had thought this was a good way to
maintain the batteries. Unfortunately we are now down to about 12.1
volts after about a 60 amp discharge. I have done a 5 hour 15.5 volt
equalization and it now goes down to about 80 amps before it reaches
12.1 volts. I feel I should expect it to go down 200 amps before it
reaches 12 volts. Should I equalize again? Did I get bad batteries? or
am I doing something wrong? I have checked all connections and
separated the batteries, they don't discharge by them selves and they
go down in voltage at the same rate. Any suggestions would be helpful.
We are hoping to go to Hawaii in May from La Paz.
Thanks
John
S/V Pangea
Swan 38