Thinking about upgrading to AGM batteries

[BillWilliams]

We have a 1999 Formula with a MerCruiser 310 (454 cid). I am thinking about upgrading to AGM batteries. I just wanted to check if it's a simple swap or do I need to worry about the charging system? Also any other thoughts/advice would be appreciated.

Thank you

 

[tpenfield]

AGM works like regular batteries from a charging perspective. So, it should be no issue. There are chargers with AGM profiles, if you run them down substantially, but for general use it should be fine. Not sure if your shore power charger has various settings. I know my 1996 Formula 330 was pretty basic.

My current boat had 7 '31' size AGM batteries, and they charged from the alternators. Shore power had an AGM setting.

How many batteries in the 260SS? 2?

 

[Lou C]

I added AGM batteries to our 2007 Grand Cherokee & 2017 Subaru with no issues….might consider them for the boat next time.

 

[BillWilliams]

Thanks. 2 batteries and no shore power so no charger to deal with

 

[Lou C]

Might just want to check the charging voltage of your system, AGMs don't do well if they get overcharged.

 

[BillWilliams]

Has anyone modified their charging system for AGMs? If so, what did you do?

 

[jimmbo]

Stick with Flooded Wet Cell Batteries, I know they aren't as Glamorous as the AGMs, but they are just fine

 

[tpenfield]

Has anyone modified their charging system for AGMs? If so, what did you do?

You could reach out to Formula 'TAG' (Technical Assistance Group) for any guidance they have on AGM batteries.

 

[Scott Danforth]

y'all overthinking the charging issue of AGM. if you want AGMs , bolt in and go boating.

if you want a SLA or VRLA, bolt it in and go boating.

an AGM can take more amperage when charging (while maintaining voltage) than a lead acid. so your standard alternator charging profile for a lead acid just doesnt charge the AGM as fast as you could..... so drink a beer while you boat a few minutes longer.

now, if you went from AGM to simple lead acid, the charge current would be too high and you would boil the batteries.

in either case, clean the connections and seal with marine electrical varnish

if you want LiFePO's then you need to add all sorts of gadgetry and pull your hair out.

 

[dingbat]

Personally, I’d stick with lead acid.

They sound better on paper, but in practice there is no concernable difference other than cost

Five out of the six AGM batteries I’ve run didn’t make it out of warranty (3 yr). Shorted internally. The sixth is currently in its second year of use.

The upside is the 3 year, full replacement warranty. All five were replaced under warranty getting them to the 5 year mark which is typical of lead acid batteries, at a 50% premium.

 

[tpenfield]

. . . . if you want LiFePO's then you need to add all sorts of gadgetry and pull your hair out.

Yes, what little hair I had is now gone.

 

[BillWilliams]

Thank you all. I think you've talked me out of switching at the moment.

 

[alldodge]

Sorry, late to the party
A true AGM is not a upscaled LA

Example: Seadoo Duracell AGM last not much longer the standard LA, mostly maybe 2 to 3 yrs

Odyssey AGM has been installed in same seadoo for now on 8 yrs and still going

Had LA Bats in Formula 27PC cruiser and changed to Lifeline AGM and they lasted 6 yrs where standard LA Bats lasted 3 yrs and that was a maybe in most cases

No data yet on new boat, but removed Merc AGM and replaced with Odyssey AGM this year. Time will tell

Thru my time with AGM Bats there are true AGM and cheaper AGM. The true AGM Lifeline, Odyssey, Trojan and others need to be charged at AGM levels. The cheaper AGM need standard LA charge profiles

Just my opinion