Going to AGM batteries. Conflicting information in the process

N

New Horizon

Member
Nov 1, 2018
104
Boat Info
420 Aft Cabin MY 1997
Engines
Twin 3116 Cats.
I just purchased 5 new AGM's. I was told when you go from flooded batteries to AGM's you need to replace the voltage regulators on a my 3116 CATs? Is this fact?
 
I believe the CAT alternators put out (forget the exact #) about 14.2V and the AGM's work quite well with that voltage, so no need.

However, it might be beneficial to upgrade the battery charger to something that has an AGM charge profile if you don't already have one. Might just need to reprogram it to an AGM setting. The AGM like to be maintained at a slightly higher voltage.

I got 8 and 9 years out of my last set of Eliminator (Deka) AGMs. I think you'll be happy.
 
Does your charger(s) have and AGM setting? The one on my last boat didn't and I had to change it when I switched to AGMs.
 
Charger is new and has the appropriate settings for AGM batteries. Any other items need to be upgraded when switching to AGM's? Thanks everyone.
 
I screwed up an AGM once with a regular maintainer.
Fwiw:

”AGM batteries have special charging needs. Some battery chargers offer an AGM or Absorbed setting to meet those special charging requirements.

An AGM-compatible battery charger sends more amps into a lead-acid battery while keeping the voltage less than 14-15 volts. AGM chargers go through the three charging phases (bulk, absorption and float) just like a regular charger. However, a regular charger could exceed 17 volts when charging a battery.”
 
Interstate dual purpose m24 flooded have always gotten me 5 yrs on great lakes with outdoor cold storage in winters. Don’t know what to expect from their $100 more AGM version but tempting. .
 
I have a lot of batteries. Most are large, thinking 8d, though not positive. All of the engine related are 24V. House set, same batteries but wired for 12v. Then genset has its own battery.


Our boat has a much higher degree of redundant systems than the sea ray boats we have owned in the past.

All that said is to put the following statement in context.

First time I had one of the battery banks needing replacement, my first thought was AGM.

Short answer my mechanic suggested we do the math of cost versus lifetime. He presented numbers which showed AGM on the genset and not going AGM on the other banks.

4-5 years later his math is tracking.

My observation, the correct answer is not the same for all boats, all usage profiles.
 
+1 on AGM‘s and my charger has a setting to switch between the two different types.
 
FootballFan said:
Short answer my mechanic suggested we do the math of cost versus lifetime. He presented numbers which showed AGM on the genset and not going AGM on the other banks.

4-5 years later his math is tracking.

My observation, the correct answer is not the same for all boats, all usage profiles.
Click to expand...

Usage varies by boat and owner, but...

Longevity also varies with AGM quality. Odyssey and Lifeline both seem to offer longer lifespans than other brands. At even higher costs, of course.

We got 11 and 12 seasons from two Odyssey banks on our previous boat... first was only replaced to create a better (Lifeline) configuration to supply an inverter... and the second bank was still going strong when we sold. Using Lifeline AGM 8Ds now for our 24V banks... but only just changed so don't have lifespan info yet.

Two of our main 24V banks are easy to reach, but the third is not. The genset battery isn't all that easy to reach. I've switched to AGMs to eliminate most service work. Cost was only a less important factor.

-Chris
 
New Horizon said:
I just purchased 5 new AGM's. I was told when you go from flooded batteries to AGM's you need to replace the voltage regulators on a my 3116 CATs? Is this fact?
Click to expand...
Not fact. Actually, your alternators have internal voltage regulators. Now if you wanted to optimize the charge profile when the engines are running then you need to step up to Balmar alternators with external adjustable multi stage controllers - but is it worth the several thousand dollars to do that? No.
All of my boats were moved to AGM when battery change was needed. The big thing I noticed is corrosion in the engine room essentially went to zero. Hydrogen Sulfide is no longer being vented from the batteries.
In the larger boats like ours we typically operate the generator whenever the boat is away from shorepower. To make the best use of what AGM batteries offer then the charger/converter should have the capability to profile the charging to AGM.
The only thing I'd be wary of is if the boat's charger is the old ferro-magnetic voltage blaster which will not be the choice for any battery.
 
FootballFan said:
I have a lot of batteries. Most are large, thinking 8d, though not positive. All of the engine related are 24V. House set, same batteries but wired for 12v. Then genset has its own battery.


Our boat has a much higher degree of redundant systems than the sea ray boats we have owned in the past.

All that said is to put the following statement in context.

First time I had one of the battery banks needing replacement, my first thought was AGM.

Short answer my mechanic suggested we do the math of cost versus lifetime. He presented numbers which showed AGM on the genset and not going AGM on the other banks.

4-5 years later his math is tracking.

My observation, the correct answer is not the same for all boats, all usage profiles.
Click to expand...
I'm with you Mark - 12V AGM GRP 31 on the generator and Low Maint Wet 8D's in series for Thruster, Port and STBD engines. I'm at 6 years for the two 8D's for the thruster and 5 years for the four 8D's for the engines...
 
Jus Cruisin said:
I see West Marine has their AGM batteries on sale this weekend. 20% off. I don't have them and I have never researched who actually makes them.

Didn't want to start another thread. Just added a post to this one.
Click to expand...
I believe West Marine AGMs are exactly the same as the Duracells sold by Sam's Club. Both are made by East Penn. Even on the current sale, there is still a +$100 delta on Group 31's between Sam's and WM. While Sam's full price is great, they usually put marine batteries on sale around now and that's an even better deal.
 
I'm not sure who makes the WM version, but the Duracell version from Sam's is made by Deka and about 50% less. Same as the Intimidator line. I believe anything with the grey bottom is Deka. I was at 8-9 years on the last set.
 
I like AGM's but I use 8D's and the AGM price of an 8D is like 3x the cost of flooded. So it doesn't make any sense. I get 6+ years out of my Nappa flooded 8D's. Your not going to get much more then that out of AGM's.
 
I've gotten 11 and 12 seasons, respectively, from banks of Odyssey AGMs. And that's slightly conservative since I replaced the 11-season bank prematurely with more capacity for an inverter install, and the 12- season bank still seemed fine when we sold that boat.

We're currently using 3 banks of Lifeline 8D AGMs, partly to reduce off-gassing, partly because I don't like doing the maintenance. (Got other stuff to mess with...) Ideally we'll get better longevity too...

And I'll probably be replacing our dead 2-year-old genset battery with AGM sometime later this week... in this case also aiming at a lower self-discharge rate...

-Chris
 
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