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  #1  
Old 04-07-2019, 03:46 PM
Npkman Npkman is offline
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Default Charging AGM vs. Wet-cell Batteries

I am replacing the cranking battery on my boat and am seeing conflicting information depending on where I look. My boat currently has a 24 volt Minnkota with two trolling motor batteries (wet-cell) and a single cranking battery that also runs graphs, livewell, etc. The on-board charger is about a 2006 vintage ProMariner Prosport 20 Plus model 41220 three bank charger. I was looking at getting an AGM battery but some places indicate that only a charger made for AGM batteries can be used while other places indicate that conventional non-AGM chargers can be used.

I'm not sure about my current charger but suspect it does not adjust for AGM batteries. I'm trying to determine if an AGM battery is OK with my current setup or if I should only get a wet cell battery. I've tried looking in WC archives but don't see where this issue has been answered before. Thanks for any help you may have.
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Old 04-07-2019, 08:43 PM
x4flatfish x4flatfish is offline
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I am going to guess that a charger that old will not support agm batteries. My advice is call pro mariner Monday am and ask them. They will steer you in right direction. You will get conflicting "opinions" on sights like this...
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Old 04-08-2019, 12:55 AM
REW REW is offline
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If you read this white paper you will find that the AGM batteries require a charging voltage of 2.4 volts per cell. However, when fully charged, the voltage should be reduced to a float charging voltage of 2.2 to 2.3 volts.

But the typical lead acid battery charger uses a full charging voltage of 14.4 volts or 2.4 volts and even when fully charged holds the voltage at the same 2.4 volts.

One could likely use a conventional lead acid battery charger with 2.4 volts per cell, if the charger was removed from the battery - just as soon as it was charged to 100%.

However, since it is difficult to monitor a battery and know precisely when the battery gets fully charged, it is easy to "cook" or "overcharge an AGM battery using a conventional lead acid battery.

Best wishes.

p.s.
One way to get around this issue with the least hassle if you insisted on using a conventional lead acid battery would be to put a timer on the power cord so that you could set the amount of time that the charger will be on for a particular charging session. After using batteries for a while one gets accustomed to the state of charge of the battery and can develop a table for charging time with a known set of batteries and a known charger.

Good luck
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Old 04-08-2019, 05:37 AM
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Bobby Winds Bobby Winds is offline
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Quote:
Originally Posted by Npkman View Post
I am replacing the cranking battery on my boat and am seeing conflicting information depending on where I look. My boat currently has a 24 volt Minnkota with two trolling motor batteries (wet-cell) and a single cranking battery that also runs graphs, livewell, etc. The on-board charger is about a 2006 vintage ProMariner Prosport 20 Plus model 41220 three bank charger. I was looking at getting an AGM battery but some places indicate that only a charger made for AGM batteries can be used while other places indicate that conventional non-AGM chargers can be used.

I'm not sure about my current charger but suspect it does not adjust for AGM batteries. I'm trying to determine if an AGM battery is OK with my current setup or if I should only get a wet cell battery. I've tried looking in WC archives but don't see where this issue has been answered before. Thanks for any help you may have.
PM sent to you.........

Bob
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Custom designed and built rod holders
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All towed with my Trusty G2 '07 Toyota Tundra
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Old 04-08-2019, 08:16 AM
Npkman Npkman is offline
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FYI. I just got off the phone with ProMariner customer support. They said that for their chargers they use the same charging profile for AGM and wet-cell batteries. He looked up the specs for my particular charger and said that it was suitable for either AGM or wet-cell batteries and I was good to go if I decide to get an AGM replacement.
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Old 04-08-2019, 08:30 AM
Ozark Bob Ozark Bob is offline
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I would be asking the battery manufacturer what charger to use. Bob
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Old 04-08-2019, 11:23 AM
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Bobby Winds Bobby Winds is offline
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Quote:
Originally Posted by Npkman View Post
FYI. I just got off the phone with ProMariner customer support. They said that for their chargers they use the same charging profile for AGM and wet-cell batteries. He looked up the specs for my particular charger and said that it was suitable for either AGM or wet-cell batteries and I was good to go if I decide to get an AGM replacement.
Yep GREAT little charger..........especially for the money.......
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2015 Polar Kraft Frontier 179WT
2015 E-TEC 90 HO
2015 Trailmaster trailer
Lowrance HDS7 Gen 2 Touch unit networked to a LMS 520c
Lowrance Engine Interface cable
Minn Kota Power Drive V2 US2 now with i-Pilot
Custom designed and built rod holders
Custom designed and built down rigger platforms
All towed with my Trusty G2 '07 Toyota Tundra
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  #8  
Old 04-08-2019, 12:13 PM
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cyber16 cyber16 is offline
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Yes most standard automatic flooded cell chargers will work.
Keep in mind most AGM batteries like a slightly higher float charge.
Most profiles set for flooded are float set @ 13.2v where as many of the AGM's like it to be 13.4v-13.8v
while in float

Most AGM's will have a label on them providing both Cyclic charge & float charge voltages
Again most AGMs Cyclic charge falls between 14.4v - 14.8v
It's always best to seek the data from the maker of such battery
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Old 04-08-2019, 12:36 PM
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Albertan Albertan is offline
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I just replaced my circa 2009 Minn Kota MK106 and MK345 chargers. Both had it written right on the case that they worked with wet cell, AGM, and I think gel batteries.
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Old 04-08-2019, 12:50 PM
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cyber16 cyber16 is offline
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The Minnkota NON-PC chargers are fixed profile set to "Flooded Lead-Acid"

The Minnkota MK-PC charger has several profiles to choose from

CHARGING PROFILE @ 25 C / 77f
Battery Type------------------Absorption------Equalize---Float
Flooded Lead-Acid-------------14.4v----------15.5v-----13.2v
AGM/High Performance AGM--14.4v----------N/A-------13.4v
(Absorbed Glass Mat)
Gel------------------------------13.9v----------N/A-------13.4v



If you use Gel cell batteries, only use a charger profile that supports them
Not doing so will create suspended bubbles within the Gel during Bulk & Absorption stages, in short order will decrease the battery capacity due to these bubbles making contact with the plates reducing their functionality

Last edited by cyber16; 04-08-2019 at 12:53 PM.
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