AGM Batteries

[mjwilly]

Hoping to get some education on AGM batteries...

Have a 2017 257 Fisherman w/ twin 150 Yamahas w/ 2 Deka Intimidator 8A27M AGM batteries. Last year I periodically got an error message that the sounder display voltage was too low, while at dock with engines off and when out trolling w/ 1 engine running. Didn't think much of it as was infrequent (admittedly, I am not savvy about these things), but this year when launched, I noticed the radio came on independently and since then the starboard engine trim is super slow and the engine does not turnover when battery selector is on that bank. When checked, the battery registered at 11.4 volts and was obviously discharged and unable to recharge. Boat is winterized/stored/serviced by dealer.

While not mechanically inclined as others on this site, I do have an interest to learn and understand how things work (or in this case don't), so was wondering if others have had issues with AGM batteries after 2 yrs (~ 300hrs)? Would this be "lemon" situation with the battery or perhaps caused by something else that I may have done? Thanks!

 

[seasick]

Maybe a lemon. When you say that it was unable to recharge, what do you mean exactly. If you start on the other battery and then switch to the 'bad' one, does it take a charge over time? (What is the voltage on the gauge when that motor is running on that battery. I ask to make sure that the motor is actually trying to charge the second battery. There could be a problem with the motor's charging circuit.

 

[mjwilly]

Thanks. Yes, when I start on “both” and then switch back to the battery bank, it does not take a charge over time. I’m afraid I don’t know what the voltage is when running on the battery - not sure the Yamaha 6YC displays a numbers, I only recall seeing a graphic.

 

[dogdoc]

A stored battery in the north east (MA) should be on a maintainer and over 3 years of winter storage without does not surprise me the battery went bad. I would try to restore with a maintainer desulfator I have used Battery Minder products with good results for this many times. Will not make it brand new but may save buying new batteries. I would do both batteries independently rather than in parallel due to differences in current voltage/capacity. When equalized (if you can) or you get new batteries you can do this in parallel. Buy yourself an inexpensive digital multimeter they are an essential tool on boats. Take a picture of your battery set up before disconnecting things to make putting it back together easier and label the wires. As for AGM I dont spend the extra money. Flooded batteries if maintained properly and kept charged will last just as long for less money. Good luck

 

[mjwilly]

Thanks! I do believe the batteries were trickled over the winter, but note taken. Will purchase a digital multimeter for sure. Appreciate the information and advice!

 

[seasick]

The first measurements would be to measure the standing voltage of each battery. That is the voltage with nothing running or connected ( battery switches OFF)
Note those numbers.
Now start the motors using whatever battery selection works (like BOTH) and then change the switches to individual battery ( ONE or TWO) for each motor.
Let the motors idle at a bit higher rev setting, like 1100 or so and then while running, measure the voltages at the batteries. That should 1 to 2 volts (approx) higher than the standing voltages recorded first. If one battery is really run down, the difference could be 3 volts or there about.
If the voltage at one battery is low in the range near what the battery measured at rest, the motor is not charging the battery.
Let us know.
Remember to never switch a battery switch through the OFF position when the motor is running. ONE to BOTH to TWO is fine and TWO to BOTH to ONE is fine.

 

[dogdoc]

just curious what is the onboard charger for your boat. i have looked around the net and cannot find any specifics noted

 

[mjwilly]

Thanks guys for all the helpful information. I appreciate this site and the insightful information posted here.

@dogdoc - The boat did not have a factory charger installed when purchased... I have been considering adding one though.

@seasick - Appreciate the step by step directions and clear expectations. Unfortunately, I won't have the opportunity to follow through with your suggestions to further investigate the issue... I had put in a call to my dealer about the issue over the weekend and they got back to me today that Grady White agreed to not only replace the "dead" battery, but also the 2nd battery under warranty (after 2 seasons), and they replaced both of them!

It is great to have a dealer that's so responsive (and close to my marina) and thankful for Grady stepping up and covering the batteries/installation. One reason why this is my 4th Grady over the last 25 years.

 

[seasick]

Great service! Let us know how things go

 

[Paul_A]

mjwilly in case you never noticed I know that the Garmin and Furuno displays I've had let you see what the battery voltage is. I glance at that number a couple times a day while running.

Don't know what you have on your dash but battery voltage is likely in the menu. Just a thought.

 

[seasick]

mjwilly in case you never noticed I know that the Garmin and Furuno displays I've had let you see what the battery voltage is. I glance at that number a couple times a day while running.

Don't know what you have on your dash but battery voltage is likely in the menu. Just a thought.

That voltage data is not super accurate but it is generally wrong by the same amount As a relative reference, it is OK

 

[mjwilly]

@paul-A... Thanks. I will look for that on my RayMarine when I go to the boat tomorrow.