390 Motor Yacht batteries

[ManteoMike]

Getting ready to replace my batteries in a 390 Motor Yacht with 480CE diesels. Trying to decide if I should switch from Interstate 31P-MHD (commercial heavy duty) to Interstate SRM-31 (marine deep cycle). Reason I am considering deep cycle is that I expect to be anchoring out a lot this year. I would like to be able to maximize time needed before it is necessary to run generator. Really do not want to make any wiring changes. My understanding is the deep cycle batteries are better house, but not as good starting .

Currently there are 2 battery banks, each bank starts an engine and is also a house bank. So no dedicated house bank. Each bank has a total of 1900 CCA. If I switch to deep cycle each bank would have about 1300 CCA. Cummins spec says you need 1250 CCA for the 480 CE. So SRM-31 should work as starting but be better house batteries.

Any one using deep cycle batteries for starting/house banks? Any ideas?

Thanks,
Mike

 

[ranger58sb]

First, most 12V batteries labeled "deep cycle"... aren't. Instead, they're usually dual-purpose... which has it's place... and that place is very often servicing dual start/house loads.

Lifeline deep cycle 12V batteries are probably an exception. At least they do rate their deep cycle batteries to approx 1000 life cycles. (I dunno how Interstate rates their batteries; you could check that.) OTOH, Lifeline AGMs are fairly expensive.

CCA are additive. If a single 12V battery gives you 1300 CCA, then two batteries together in parallel to 12V will give you 2600 CCA. Et cetera. How many batts in each of your banks?

You might compare the Interstate products to Odyssey/Northstar and Lifeline products, which are more expensive. We used banks of dual-purpose Odyssey Extreme G31s in our previous boat, got 11-12 seasons from those.

-Chris

 

[ManteoMike]

Chris,
Thanks for the reply.
There are 2 batteries in each bank. CCA numbers I mentioned are combined (I added cca of the 2 batteries, like you said.) .

Will check out brands you suggested.

 

[ranger58sb]

Kinda puny cranking amps, and I don't see a capacity spec (usually Ah @ 20hr rate).

East Penn 8A31DTM AGMs are 800 CCA and 105-Ah... and they have other flooded options.

DEKA SLI Spec Sheet 0007 (eastpennmanufacturing.com)

The Odyssey Extreme ODX-AGM31s we used are 1150 CCA and 100-Ah.

Extreme Series Battery Specifications | ODYSSEY® Battery (odysseybattery.com)

I mention AGMs only because ours were located were servicing wasn't all that easy. Flooded options could well be fine for your situation.

-Chris

 

[ManteoMike]

Chris,
Thanks for info. Interesting specification sheets.

Mike