One new battery

[Ck2hans]

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

[Fratto]

Chuck: I looked around for fun to see if anyone would provide a recommendation here. As i expected, all I could find was multiple articles from simple to complex stating that neither the new battery nor the old ones will be happy. Since they are already 4 years old, my bet is that you will loose the whole bank in short order.

If you do this, keep us updated on how long the bank performs. It is always fun to have some real world input vs all of the theory.

[Ck2hans]

Mark:
In my endless research of batteries over the years most articles say ALL batteries must be replaced at the same time or the old one’s will fail shortly. I have also read various articles stating that replacing all theory is an old wives tale brought on by battery manufacturers to sell more batteries.

As most know I run private yachts for a living. In my professional life I deal with large banks of batteries. The yachts themself have multiple banks of batteries for main engines, generators, electronics, & house batteries. The tenders have batteries for each outboard engine (up to 4), generator, bow thruster, house and electronics not to mention the batteries in the toys I.E. jet skis, golf carts, etc.

Various times I have been in remote locations where purchasing a complete set of batteries is impossible and get one or two is difficult, so I have replaced the problem battery only with the intention of replacing the rest in a few months when returning back to home port. As life goes, other things happen/take priority and the other batteries never get replaced.

Over the years (40 of them) I have never had a catastrophic failure of the remaining batteries, and for the most part have gotten the remaining life (2-4 years ) out of the original batteries. These successful experiments have been with someone else batteries/money. Hopefully Murphy’s Law doesn’t come in play with my own batteries. LOL

Chuck

[Fratto]

There is no substitute for your kind of real world experience ... thanks for sharing. I am looking forward to seeing the results of this experiment.