Just removed all 8 of my 4D AGM batteries to replace my R-14 & R-12 relay valves. Checked the resting voltage after 24 hours of removing the batteries. 7 of the 8 showed 12.80 to 12.83 volts, one showed 11.72. Tried to charge the weak battery but no good.

Batteies are 4 years old, all but one showed great resting voltage. I know it’s not always recommended, but I am only replacing the one battery. Any suggestions as to putting it (the new battery) first inline, last inline, or somewhere in the middle?

Chuck