New Batteries

[eje]

It's time for new batteries. The boat is set up with two batteries & the std 1/2/both/off switch. I don't have room to add an additional battery with modifying the battery compartment.
I have two dual use series 27's. I'm wondering if might make sense to switch to one dual use & one deep cycle. I'd use the deep cycle for the primary house, the dual for starting & secondary house

[sailorboy1]

Are there even true group 27 deep cycle batteries?

I think it probably doesn't matter for a boat small enough to only have 2 group 27 batteries

[S/V Illusion]

Presuming this is a small diesel, you don’t need anything special to start it. Your best option might therefore be two separate deep cycle batteries. There as as many good options as there are opinions - it’s not a black or white choice.

[JimsCAL]

A 12 volt "deep cycle" battery will start your engine just fine. You might check to see if you can fit Group 31s. Not much bigger than a Group 27 and a bit more Ahr capacity.

[Wotname]

Agree with the above 3 posts!

[Shanachie]

If height in the battery compartment allows, I would go with two 6-volt golf cart batteries (Duracell) wired so they become one 12-volt battery.


They cost about $100 each at Sam's Club and will provide 225 amp hours. Tough as hell, as long as you add water once in a while. Much better than the "dual-purpose" batteries most places sell -- and much less expensive.



You can find wiring diagrams on the web, but basically you connect one cable to a positive on one battery and negative on the other. The remaining posts become your positive and negative posts.


You can pay twice as much and get Trojan, but I don't think the extra price reflects added value. The Trojans are a little better, but not that much.


If you're paranoid about batteries, you can add a start battery somewhere else in the boat. But it's not really necessary. TowboatUS or Seatow will give you a jump in a fix.