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Old 01-12-2021, 12:50   #1
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Join Date: Nov 2011
Location: Australia
Boat: Fontaine Pajot Salina 48
Posts: 18
AGM Battery Life


Following my previous post on voltage drop across AGM deep cycle bank whilst amp level remains high. There seems a real possibly of battery failure after 18 months of use because of heat.
Manufacturer now has new statistics on batteries which show 2 years life cycle if mounted in area >40c.
Mine are in the engine room as was the previous bank for 8 years however these new ones seem to be challenged.
So question. Does anybody have any brand reference experience of use of deep cycle AGM's mounted in engine rooms?

Thanks again for feedback
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Old 01-12-2021, 13:10   #2
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Location: Solomons, MD USA
Boat: Formosa 51 Aft Cockpit Ketch - "Beausoleil"
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Re: AGM Battery Life

In our Formosa 51, the engine start battery (Fullriver DC200-12 AGM) and the house bank (4 x DC400-6 AGM) were both in the engine room - below the salon sole - and we never had a heat problem while cruising the southeast US coast, Bahamas and the eastern Caribbean for 5 years.

The engine room is well ventilated and rarely got above 95-100F/35-38C. The batteries lasted until about two years ago - for a total of 12 years. The key was to not discharge below 60%, and to charge them completely. A 720W solar array was the answer, as well as over-redundancy on shorepower/genset charging + high-output alternator.
Cap'n Jon (KB1HTW)
S/V Beausoleil -1979 Formosa 51 Ketch
"If it's gonna happen, it's gonna happen out there." - Captain Ron
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Old 05-12-2021, 08:27   #3
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Location: Maryland, USA
Boat: 58' Sedan Bridge
Posts: 5,514
Re: AGM Battery Life

We have installed both Odyssey and Lifeline AGMs in our engine room; the Odysseys lived for 11/12 years each bank. Didn't have the boat long enough after that to evaluate the Lifelines, but I think they were on year 4 when we sold.

Chesapeake Bay, USA.
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Old 05-12-2021, 10:38   #4
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Location: Cowichan Bay, BC (Maple Bay Marina)
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Re: AGM Battery Life

Every time AGMs come up, I try to remind users of these helpful contributions from Maine Sail:

AGM Batteries - Making The Choice (from Maine Sail)

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"

Additional Observations on the Limits of AGMs,5....html#msg63004
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
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