replacing 4d battery

[rblatter]

I have a question on batteries. My boat has 3 lead acid batteries group 31 and one 4D, huge thing. Now that D battery as been there for the last seven years, and keeps testing o.k. for now. It runs the accessories and the outside cockpit fridge, we can stay three nights on the hook without problems. The question is, what should I replace that D battery with, my dealer mentioned two more 31s... I am reading all this and the AGM batteries are intriguing... would I have to change all batteries...

R.Blatter
310 Sundancer 2001
Bravo IIIs 5.7L

 

[wingless]

When batteries are connected in parallel, then they should be nearly identical, so they don't work against each other.

Most battery chargers have isolated outputs, for their two or three battery systems.

When batteries are isolated, then its okay to have different vintages.

When replacing my six 31's I considered the larger batteries, then looked at the cabling and tray changes and remained w/ the existing form factor.

The increase in capacity was very small for all that effort too.

 

[Four Suns]

Did your boat come with that 4D from the factory or was that an aftermarket thing?

 

[rblatter]

Gary,

The 4D was installed after, by the dealer.

R.Blatter
310 Sundancer
Bravo III 5.7Ls

 

[vernh59]

Great timing for this info as one of my 2 year old LA batteries took a dump on me last weekend. I hate changing batteries so maybe I'll switch to the AMG this time.