How many volts should I be getting on an AGM starting/charging battery?

[biggamefisher]

Originally Posted by vtec

I checked this morning after a full charge yesterday and got 12.85v at the battery and 12.3-4v on GPS. I didn't try the backlight thing as I didn't see the post. Thanks much on the input and battery education.

Maybe the old charger may be suspect or not capable of charging an AGM. I would check the battery voltage daily to ensure it doesn't continue to drop. Looks like the new charger did the job.

[GBS]

FYI - I chased a low voltage problem a lot this spring. Turned out it was my Carbon unit - it routinely reports about .5 v lower than the actual line voltage measured at the pins on the back.

[TomP.]

Originally Posted by biggamefisher

Maybe the old charger may be suspect or not capable of charging an AGM. I would check the battery voltage daily to ensure it doesn't continue to drop. Looks like the new charger did the job.

This is exactly what I was thinking as he never mentioned what he had for a charger as far as outputs or AGM compatibility..

[vtec]

Originally Posted by TomP.

This is exactly what I was thinking as he never mentioned what he had for a charger as far as outputs or AGM compatibility..

The last charge was with a fairly new 3amp Battery Tender. The other charges were with an old sears Die Hard 10amp and a 5 or so year old 2amp Shumacher trickle charger. Do I need a special AGM charger? Again this is for a combo starting/deep cell for electronics.

[bbheli]

Originally Posted by vtec

I seem to have poor luck with batteries so when I replaced my starting/charging battery I spent the money on an AGM last year. I have put it on a small charger periodically before I head out. I get on the water and drive a distance and within minutes after shutting down I have only 12.2-3 volts on my LCX25 registering. Boat sat for a week and this morning I was checking other stuff, turned on electronics to check and I had 12.2v and it started to drop within minutes. I don't think this is normal but I have only had lead acid batteries. I put it on the charger for the day and will check the voltage tonight. I will also check at the battery with a good tester.

Question is do I go back and try to get it replaced? Thoughts?

Maybe you know this maybe you don't and maybe others will have opinions. My recent research buying new batteries concluded that AGM is not the best for the start battery as they are best for short bursts of current (starter) in which case lead acid is better. AGM is better suited for trolling motors and charts and the effect of the constant drain recharge.

[Ozark Bob]

Depends on which AGM and if it is also responsible for other things.(finders etc.) Agm of proper spec's is fine for dual purpose. I picked up on Vtecs 3 amp (charger). It may be the low charge is not enough to top off your battery. The longer the battery is not fully charged(immediately following use) the more the battery ages. 3 amps is only a maintainer for a full size AGM.(keeping it at 100%). JMO Bob

[DW]

^^^

x2

An AGM is better for the task in all respects except it will cost more than a wet cell. The important consideration for any battery used for cranking is that the CCA rating of the battery meets or exceeds the motor specification listed in the owner manual.

A maintenance charger is ill suited as an onboard battery charger.

[bbheli]

Originally Posted by DW

^^^

x2

An AGM is better for the task in all respects except it will cost more than a wet cell. The important consideration for any battery used for cranking is that the CCA rating of the battery meets or exceeds the motor specification listed in the owner manual.

A maintenance charger is ill suited as an onboard battery charger.

Confusing, that is not what mechanics from 3 different Mariana's told me when I had to buy new trolling motor batteries on a recent trip. I called around looking for batteries and asked which is better specifically for trolling motor. They all explained starter should be wet as its better for short high current bursts and AGM better for trolling with sustained discharge. They were not trying to sell me what they had in stock so not sure which answers are correct.

[biggamefisher]

Originally Posted by bbheli

Maybe you know this maybe you don't and maybe others will have opinions. My recent research buying new batteries concluded that AGM is not the best for the start battery as they are best for short bursts of current (starter) in which case lead acid is better. AGM is better suited for trolling motors and charts and the effect of the constant drain recharge.

A short burst of energy is exactly what you need to start an engine.......your comment is confusing. That being said.........AGM's are considered true dual purpose batteries, meant for both applications.

Can you post a link to where research would point to being otherwise?

[biggamefisher]

Originally Posted by bbheli

Confusing, that is not what mechanics from 3 different Mariana's told me when I had to buy new trolling motor batteries on a recent trip. I called around looking for batteries and asked which is better specifically for trolling motor. They all explained starter should be wet as its better for short high current bursts and AGM better for trolling with sustained discharge. They were not trying to sell me what they had in stock so not sure which answers are correct.

Those three mechanics better go back to mechanics school! LOL

Maybe go back and ask those mechanics why so many vehicle manufacturers are switching to AGM? Why are race batteries AGM? They start engines, no?

AGM's are true dual purpose batteries, they can provide the short term energy to start an engine and also provide/supply long term draw demands.