Replacement Battery for 2011 350 Sundancer

[argus1]

Dealer is recommending that I replace the lead acid batteries that in my 2011 350 Sundancer (Twin MerCruiser 377 MAG ECT Bravo III sterndrives DTS with Axius joystick). The current battery is Interstate 27M-XHD 800CA. Two the batteries tested weak. To be prudent, I want to replace all four. The service tech told me that Mercury recommends AGM batteries for my boat.

What AGM battery is recommended for my boat? I see that Sam's has Duracell AGM Deep Cycle Marine and RV Battery (Group Size 31); will this battery work on my boat?

 

[Wylie_Tunes]

I do know if Merc rec's AGM or not, but IMO, you can set that aside, and focus on the best specs. What is the desired CA/CCA/MCA for a cranking battery? Whats the ideal reserve and/or Ah?

Could a group 31 be the better battery for your boat? Sure, but not cause its AGM, but because its a larger battery then the current. So right now, you are making an apples to oranges comparison.

There can certainly be advantages to using an AGM, but when you boil it down, a volt is a volt and an Ah is an Ah, regardless of its source.

 

[argus1]

Others on this forum have said the same thing, Mercury is recommending AGMs. So, if the MarineMax service tech is tell me this is what Mercury is recommending; do you have any information that is not true?

 

[Wylie_Tunes]

I have nothing thats states it true or false, but a rep would have to bring his A game in order to convince me why a CA or Ah from an AGM is somehow better then an CA or Ah from a LAWC. I put more stock in a quality battery of the proper size and spec, first. One could easily install the incorrect AGM.

 

[argus1]

What I am asking if others have used the Sam's AGMs 31 Group in a similar boat with good results?

 

[argus1]

I have nothing thats states it true or false, but a rep would have to bring his A game in order to convince me why a CA or Ah from an AGM is somehow better then an CA or Ah from a LAWC. I put more stock in a quality battery of the proper size and spec, first. One could easily install the incorrect AGM.

There are many references on the internet that Mercury is recommending that AGM batteries size group 27 or 31 be used with boats with a Digital Throttle System (DTS). A battery with low voltage will cause the warning alarms to go off and there are a lot. I got 5 different alarms, most were the same alarm on both engines, after starting my boat and not leaving the dock.

I am just not that knowledgeable to understand all of implications in the technical information that I reading online; but it is clear that Mercury is recommending AGMs with DTS.

 

[Stee6043]

You may want to post with a different title if you want specific feedback on specific AGM batteries.

I don't think you're going to find anyone that will steer you away from AGM. The only downside I'm aware of is cost. If cost is no object those batteries you referenced above should be decent ASSUMING 1.) your battery charger can handle AGM and 2.) your battery boxes/wires can handle the slightly larger form factor that will come with the Group 31's vs your current Group 27's.

FWIW Duracells are awesome...made by Dekka. Plenty of good reviews hanging around.

Another FWIW...if your existing batteries are wired in with zero extra slack I'd be tempted to stick with group 27's. On a prior boat of mine going to Group 31's would have been a huge PITA based on the wiring setup. It's worth taking a look before you commit to the larger battery.

 

[Little Ducky]

https://www.batteriesplus.com/battery/marine-and-boat/deep-cycle/bci-group-31m/sli31dtmagmdc

I'm using the one above..... replaced all 3 Group 27's that were in my boat last year after making sure the Group 31's would fit. I think they are 1/2" longer then the Group 27's you are replacing.

The one below from Sam's I bet is the same battery and a better price.

https://www.samsclub.com/sams/durac...e-31dtmagm/prod3590232.ip?xid=plp_product_1_1


If you do switch to AGM make sure you select the AGM program on your battery charger to get maximum charging.

 

[Todd320]

I used those Sam’s Duracell’s on my ‘07 320, (had 27s if I recall) which has a really similar layout to your ‘11 350, and you probably have a newer charger, so I would highly recommend AGMs. No maintenance, longer life, and I have had zero issues since installed. The only thing you do need to be concerned about is the space they are installed. Mine were perfect, but the trays they were sitting in just barely fit the new batteries.
They were 150$ each when I bought them, so well worth it when compared to wet cell.

 

[argus1]

Thanks all - I am headed to Sam's tomorrow to see if they have four AGM's Group 31 in stock.

I have a Protech 1230i Plus battery charger and understand that I need change the battery type selector switch to AGM; does anyone know how many hours to set the programmable absorption timer switch, one, two, three or four hours?

I have a total of four batteries wired parallel, two for starboard and two for port.

 

[paulswagelock]

Group 31 is almost an inch longer.
Those Dekas can take the same charge profile as a normal flooded cell. 2 hour absorption is usually fine since AGM charges quicker.
DTS wants AGM because it can react quicker to demand changes with a lower internal resistance. Less chance for a low voltage condition when a large load hits. More important when the battery is not dedicated. It also holds a charge longer so less likely to have a low voltage battery from a few weeks of sitting. These are some of the reasons Merc now specs them.

 

[argus1]

I don't think you're going to find anyone that will steer you away from AGM. The only downside I'm aware of is cost. If cost is no object those batteries you referenced above should be decent ASSUMING 1.)

Sam's price will be less than half of what the dealer is charging.

 

[argus1]

DTS wants AGM because it can react quicker to demand changes with a lower internal resistance. Less chance for a low voltage condition when a large load hits. More important when the battery is not dedicated. It also holds a charge longer so less likely to have a low voltage battery from a few weeks of sitting. These are some of the reasons Merc now specs them.

Service Tech told me that the low voltage from the batteries can cause the alarms to go off.

 

[Espos4]

Service Tech told me that the low voltage from the batteries can cause the alarms to go off.

Are you getting an alarm and is that the reason for replacing the batteries, or are they being replaced strictly due to age/test failure?

 

[argus1]

Are you getting an alarm and is that the reason for replacing the batteries, or are they being replaced strictly due to age/test failure?

Two of the batteries tested with low voltage. Low voltage on the batteries will cause alarms.