Battery sizing help

[Bakoboat]

Hello,
Need assistance with correctly sizing batteries for 456 carver motor yacht.
Presently have 2- 8d batteries, 1 for each engine with all house running from starboard battery.
450 Cummins diesels. This a 50 amp boat. There is an additional small battery dedicated to the generator.

Does anyone have similar set up for 50 amp boat with diesels and what batteries have been successful.

Appreciate any guidance.

Thanks

[Midnightsun]

Many boats have gone away from 8D simply because they are so darn big/heavy. In my case I have 370 Volvos with 50a 250v shore power so fairly similar. You can easily get away with a single group 31 1000cca battery for each engine assuming they are dedicated for starting only. A third bank for house is a better way of ensuring starts all the time as opposed to using one of the 8d's for house loads IMHO.

As for the house bank, the choice is yours to make, most just use multiple deep cycle wet cells either 12v or a combo of 6v to form a 12v bank sized for their needs. Personally I went all out and now have a 900AH dedicated LifePo4 house bank. Never going to run out of juice on the hook. Starting banks and generator are completely isolated, always full and ready to start.

Cummins service centre is conveniently located on the way to the boat so I am using their brand, very content with the performance/price so far. Unfortunately they have almost doubled in price since 3 years ago when I installed them. https://shop.cummins.com/CSSNAStore/s/p ... ng-battery

[Coldcruisin]

Interesting setup Midnight Sun. Thanks for the insight.
I have 3 8D's on my 450, 4 group 31's and 1 group 27. The 3rd 8D is a dedicated house with one for each engine (Volvo 480's). Conventional wisdom would dictate a dedicated house battery without the worry of running down a starting battery but I dont know how your engine bay is set up. Very curious on the LifePo4 battery as a house...

[Midnightsun]

See here. viewtopic.php?f=12&t=6315&hilit=LifePo4