Oh crap...Battery question.

[Rooster Rick]

My house/cranking battery is a Duracell AGM 31 (Sams Club), installed June of 2020. Running a Mercury 115 4 stroke and one graph, Garmin 93, rarely any other accessories. Two more of the same batteries power my 24v trolling motor, dedicated, all charged by a MK330D; always charging when not on the water. I over 300 hours last season, a lot of run-and-gun type, and never an issue, even after 10-12 hours on the water. Over the winter I added another Garmin 93 graph, and upgraded TM to a 24v Ulterra. So, the first time out this last weekend (tough bite) I was on the water about 5 1/2 hours, running both graphs, mostly using the TM, but ran the big motor about 1hr. Noticed my graph showed 12.2v, thought “oh s#@t”, and sure enough, couldn’t crank the big motor. Made it back on the TM, and got loaded fine. Back in the garage, charged for 2 days, let it rest for 12 hours, and reads 12.5v (House/cranking battery) Seems I have a problem, how do I diagnose, is it a bad battery? Am I looking at a dedicated house battery? Doesn’t make sense to me that one additional graph would draw that much juice. Thanks.

[Coho975]

Unhook everything from it, and charge it overnight. Take it to an auto parts store and they'll test it for you.

[Ltrain]

12.5 is too low, you can put a load meter on it but with that voltage reading it's already apparent that the battery is faulty. It's under warranty so just take it back.
As far as a house battery besides the extra weight and initial cost, there's no downside. I would never go without one.

[slayerfish]

Not supposed to use deep-cycle batts for engine starting. I have those same same Duracell AGM's for my troller but have a dedicated marine cranking batt for the motor.

[OneidaEagle]

Originally Posted by slayerfish

Not supposed to use deep-cycle batts for engine starting. I have those same same Duracell AGM's for my troller but have a dedicated marine cranking batt for the motor.

SlayerFish,

I have heard that as well, but are you able to clarify as to why?

I have bene thinking of upgrading to a AGM 31, for my starter, and electronics as well.
& then your statement reminded me of others saying the same, but haw no idea why.

Thanks OE

[Rooster Rick]

Originally Posted by slayerfish

Not supposed to use deep-cycle batts for engine starting. I have those same same Duracell AGM's for my troller but have a dedicated marine cranking batt for the motor.

Hi Slayer, my understanding is that these (Duracell AGM Platinum) are dual purpose, suitable for cranking & house combination.

[Rooster Rick]

Originally Posted by ltrain

12.5 is too low, you can put a load meter on it but with that voltage reading it's already apparent that the battery is faulty. It's under warranty so just take it back.
As far as a house battery besides the extra weight and initial cost, there's no downside. I would never go without one.

Thanks, ltrain, that’s what I was thinking. Disappointing I got less than a year from it, but fully covered under the 18-month replacement. I’ll put in a new one and see how it goes before I pull the trigger on a dedicated house battery... but that’s probably where I’ll end up.

[JOHN L. HECKLSMILLER]

I have my "Crank & Boat Accessories" batteries connected in parallel. This system provides me
with increased "Capacity". And being on "Lake of the Woods"/US & Canadian waters this system has never let me down for all of the "Boat Accessories, 3 Lowrance Units & Cranking Power" for a 90hp Honda. (17yrs/4,684hrs/31,811 GPS miles & 6,048 gals) Batteries do wear-out over time, but 2 batteries in parallel has been a very reliable system.

[Ltrain]

Also if they are indeed dual purpose, then yes you can use them as starting batteries also. I used the Duracell regular flooded lead acid dual purpose for my starter and house for 2 years without issue.

[Ltrain]

Originally Posted by JOHN L. HECKLSMILLER

I have my "Crank & Boat Accessories" batteries connected in parallel. This system provides me
with increased "Capacity". And being on "Lake of the Woods"/US & Canadian waters this system has never let me down for all of the "Boat Accessories, 3 Lowrance Units & Cranking Power" for a 90hp Honda. (17yrs/4,684hrs/31,811 GPS miles & 6,048 gals) Batteries do wear-out over time, but 2 batteries in parallel has been a very reliable system.

Yep, essentially creating one big battery. Can also charge off single bank charger if you choose( just takes twice as long) .