Best heavy duty batteries.

You can't beat golf cart batteries. I like trogens but they are all decent. My 355 had a weird setup. It had 2 engine batteries for 1 and 2 engine batteries for 2 on the selector. When you had it to 1 those 2 would start both engines and do the house also. 2 would do the same. Only 2 batteries were used at once. On my 450, I have 4d batteries to start the engines and 6 golf cart batteries for the house. We can go 3 days without starting the gen with the 6 golf cart bats. They are awesome.

I like Deka Golf Cart Batteries.

Got as much as 6.5 years on the house bank, but that was pushing it..
(Ended up in the Bahamas for anchor with almost dead batteries, a frontal system kept the solar panels cloudy and I was kicking by own butt and making excuses to the crew for 3 days but my mea culpa because I did not check Date of Install before I left the dock in Fort Lauderdale)

5 years for sure. Probably the same with Trojans (and Costco)

Had a bank of Rolls and they lasted 8 years. Great product, but that is like marrying a movie star: Unless you baby them, they won't do you any better than the regular stuff: Don't go below 50% discharge, don't go too long without equalization, keep distilled water up every month, etc.

Check your starters to see what minimum cranking amps are required. Might be stated as CCA, MCA, whatever... but then be sure what you shop for will meet that requirement with decent reserve to spare.

Then it depends slightly on what batteries you have now... since footprint might be a consideration. If you have two 8Ds per engine, then you have plenty of physical space. If you have only two Group 27s per, not so much space. Depending on available space, you could gang two or more 12v Group 31s together in parallel, for example... or maybe four or more 6v golf cart batteries wired in series/parallel. Need more info to solve that, but in general golf cart batteries are true deep cycle and would probably be better for house loads... assuming you anchor out... and assuming you can get enough cranking amps.

Then there's weight. 8Ds weigh lots, individual batteries in a multi-unit bank don't weigh as much... so might be easier to handle.

Note most of this isn't yet about battery brand or chemistry.

-Chris

First, rewire your batteries so that your house, engine and generator batteries are separate.

House batteries should be on an isolated bank so that at anchor you're not depleting your starting batteries. The generator battery should also not be depleted so that if needed you can start your generator and use the AC charger to charge batteries.

I use seven batteries, four in parallel for house and bow thruster and the other three for each engine and generator.

Victron makes a nice battery monitoring system not too expensive you can install to monitor your house bank, good if you spend a lot of time on the hook. I think it's called a BMV-600.

I use Deka DC 31 lead acid batteries. They last 5 - 7 years depending on how you maintain them and you can get them at NAPA for around a hundred bucks. Deka makes the battery for NAPA, just ask for the deep cycle one.

http://www.dekabatteries.com/assets/base/0194.pdf

I also have a 3608 and did the batteries this summer. I have a separate starting battery for each engine and the genie. My house system is 4 Trojan T145 plus batteries. I use a pro-fil watering system to keep them topped up. We spent 9 days out on the water in Aug and had lots of juice. Obviously. We ran the generator in the morning and in the eve for about 90 minutes and system was excellent.

Best heavy duty batteries

Hi,
I agree with separating your batteries into 3 groups. Generator starting battery, engine starting batteries and lastly your house batteries. On our 36 Uniflite that we owned before our current 4207 Carver, I had 9 batteries in the engine room. 1 for the generator, 2 for the main engines and 6 golf carts for the house batteries. I also had a Link 10 battery monitor that showed me what state of charge my batteries were at. The whole setup worked great for anchoring long term, which the wife and I love to do.
I'm going to replace the batteries on our 4207 Carver this spring. I'm going to install 1 8D for the engine starting battery, because the Cat 3208's start as soon as you touch the start buttons, and 6 L16 golf cart batteries for the house batteries.
Al

I would install 2-8d's that you can run 1 battery for each motor, and parallel them if need be. You never know when a battery gets a dead cell, or an alternator goes bad.....