I have a 2004 Sea Ray 220 Sundeck...

[Ceeg]

I have a 2004 Sea Ray 220 Sundeck with a 5.0 MPI engine.  Going to replace my batteries before I put the boat in next month.  Any recommendations on what batteries I should use.

Any help is appreciated.

[wingless]

My boat was built using five flooded cell Group 27 batteries. They were placed in trays w/ a bar across the top to secure in-place.

They were initially replaced w/ six flooded cell Group 31 batteries. The Group 31 batteries are larger, but taper down at the bottom, so they fit into the existing trays.

My experience has been that the operational lifetime of flooded cell batteries has been unacceptable, so I switched to AGM batteries.

For my usage, the most important requirement is capacity, specified / measured in ampere-hours, Ah, so that the unplugged run time when on-hook for my electronics, but especially for my refrigerator is maximized.

THE battery with the LARGEST specified Ah capacity is the Lifeline GPL-31XT. This battery capacity is about 25% larger than every other Group 31 battery at 125Ah.

http://lifelinebatteries.com/products/marine-batteries/gpl-31xt/

My history with both the operation lifetime and with the storage capacity has been very positive, so I have no hesitation to recommend this battery.

FWIW, the charging characteristics of AGM batteries is different than those for flooded cell batteries. This Technical Manual is complete and well-written.

The AGM batteries love lots of charger current and want 0.2C to 0.5C, 20A to 50A charger current on a 100Ah battery. An AGM battery can be fully properly recharged in two hours.

The net on the on-board charger is that the existing initially-installed charger may be retained, but probably won't realize the benefits of this great battery.

http://lifelinebatteries.com/wp-content/uploads/2015/12/manual.pdf

[Lil_Rug_Rat]

I replaced mine in my Sundancer 290. Went to local Freightliner truck store and got three 1000 amp batteries for less than you can buy 875 amp batteries at parts place..They are holding up good and drain very little power in the off season. They fit right in the battery tray like any other battery. They are just stronger.

[wingless]

Yes, the Cold Cranking Amp, CCA, specification is one way of comparing batteries, but might not be the best parameter to use when comparing marine batteries.

The CCA specification defines how many amperes may be continuously delivered for 30 seconds, at 0°F, while maintaining 1.2V/cell, or 7.2V across the terminals of a 12V battery.

The battery engineers balance the trade offs between short-term bursts of high current and long-term sustained delivery of low current.

A starter turning over a gasoline engine will draw about 50 to 200 amps. A starter turning over a diesel engine can draw up to 1,000 amps. For a gasoline boat, any battery in good condition will provide sufficient current for starting.

The OP has a 2004 220 Sundeck. It has one battery, with a second battery optional. The battery switch is also optional. The OP says "batteries", so there are two.

https://bbg1.my.salesforce.com/sfc/p/#E0000000Z21E/a/E00000000UI0/aHacFR_k0RGsCumZuBFBth8UvCmW.2nQovp2R4wROH8

It is true that any / every new marine battery will start the OP's engine and run the stereo while on-hook. The OP can select fresh batteries based on cost and the boat will work.

If the OP wants to maximize the number of years between battery replacement, then go w/ AGM over flooded cell. If the OP wants maximum run time, then select the Lifeline GPL-31XT.

Regardless, the batteries should be the same manufacturer, date code and model.

[Ollie]

If you can swing it, upgrade to group 29's. They have the same footprint, are a little taller and give you more Ah. I did that and couldn't be happier with the house battery and starting battery - plenty of juice for power ring my 600W sound system all day.

[PiscesPearl]

After much research, BoatUS online had good articles, I went with 31DTM-ATM Duracell at Sams club for my 40 MY. No gasses, no spilling, and twice the capacity.

[SurLaMer]

AGMs: no maintenance, can be mounted in any configuration. Should be mated to a three stage charger to comply with battery manufacturer's charging profile.