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What kills AGM batteries?

Solar/Wind/Charging/Batteries

What kills AGM batteries?

by RBEmerson » Wed Jan 20, 2016 9:09 am

Our AGM start battery appeared to be failed. The indications were a) low voltage and b) the Magnum Energy - Smart Battery Combiner (SBC) reset itself every 10 seconds. The latter is a recognized indication from the SBC. I called Magnum Energy's tech support and, cutting to the chase, found a fuse, protecting the house battery lead to the SBC, popped. Replacing the fuse ended the 10 second reset cycle.

The battery in question is a Lifeline Start battery, GPL-1400T - AGM - 43 AH - 850 CCA

NTL, I had doubts about the batteries health. I took the battery to Treasure Coast Battery (Stuart, FL) for a load test. The tester showed about 220 CCA or functional but fading. I replaced the battery.

Now, the question: What kills AGM batteries? This battery was in place for 4 years. Its sole job is to start the motor (32 hp diesel) and run the instrument panel and booster pump while the engine is running. AFAIK, the battery was never fully discharged. When the boat has been in storage, the house and start battery are charged by the boat's solar panel. What killed the battery?
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Re: What kills AGM batteries?

by brilliantstar » Wed Jan 20, 2016 4:05 pm

Old age and misuse and any combination thereof. Age is measured in cranks for starting batteries, not years. Four calendar year old batteries can be as old as eleven year batteries (the point at which ours had to be replaced). The recharge cycle is key, as starting batteries, with their thinner plates, require different charging that deep cycle batteries with thick plates. Nigel Calder has a trove of information on this in his several books.
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Re: What kills AGM batteries?

by Scott Berg » Wed Jan 20, 2016 5:19 pm

In addition to other comments, AGM Batteries need to be fully charged every couple of weeks. This means lots of solar or a shore side battery charger. When AGM batteries are left partially charged for a long period they can badly 'sulfate' and lose capacity. Note that lifeline AGM's can be equalized... the instructions are on their website.
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Re: What kills AGM batteries?

by RBEmerson » Wed Jan 20, 2016 10:15 pm

Equalize Lifelines? I did not know that! TNX.

Otherwise, it sounds as though, even with the SBC to get the battery charged correctly, this thing was on its way out due to age, less than ideal charging, and sulfation. RIP GL-1400T. :-(
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Re: What kills AGM batteries?

by FAST FRED » Thu Apr 07, 2016 6:39 am

Why would you pay extra for an AGM to use as a start battery?

A far cheaper LA start batt will last as long , and the AGM virtue , fast recharge from deep discharge would never be a concern?

AGM mostly make sense with deep cycle house use IF the charging system is way oversized so the charging advantage can be used.
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Re: What kills AGM batteries?

by RBEmerson » Tue Apr 12, 2016 10:03 pm

Why AGM? Because the only practical mounting position is significantly (~35°) off perpendiculars at rest. AGM's give high current/volume and have low internal resistance/discharge rates when idle.
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Re: What kills AGM batteries?

by FAST FRED » Sat Sep 24, 2016 8:29 am

"Because the only practical mounting position is significantly (~35°) off perpendiculars at rest. "

You might consider sending a letter bomb to the designer or builder who did this to your boat.
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Re: What kills AGM batteries?

by RBEmerson » Sat Sep 24, 2016 8:11 pm

Um... or maybe he looked at the battery locker and concluded, as I did, there was no other option. Period.

The biggest problem with the start battery turned out to be a set of cables that needed to be sweat soldered on top of the OEM crimps. Once the cables were sorted out, the start battery became quite happy.

End of problem.
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