New batteries...old charger?

4_Ever_Newbie

4_Ever_Newbie

Member
Aug 6, 2017
47
Boat Info
260 Sea Ray Sundancer (2004). 5KW Gen
Engines
350 Mercruiser MAG MPI
I'm installing new AGM batteries in my 2004 Searay 260

Should I be concerned about the factory installed charger?...looks like it is working OK....but will charge/maintain the AGM batteries properly?....concerned it will keep them at 14v> (vs stop charging them when fully charged)

(Sorry don't know why photo comes up inverted)

IMG_7759.jpg
 
I’ve had AGMs for a year now, and have used the factory installed charger from 2007. My understanding is AGMs can use the same charging profile as the standard wet batteries. I have had no issues.
 
Agm is a construction method.

What sets voltage requirements is chemistry. (Not simply “lead acid”, but any other alloyed metals in the lead (antimony and calcium to name 2 common ones), any other additives in the electrolyte)

Get the voltages wrong you ecectrolytically remove the water from the electrolyte. In an agm, you cannot replace it.

You need to get the technical data from your battery manufacturer to find out what it’s specific voltage requirements are, and then go about seeing if your current charger can be set to match.
 
The new automated multi stage chargers are much better for squeezing the most life out of a set of batteries and have multiple charge profiles for different types. Take a look at the Pronautic series. They are reasonably priced.
 
As long as they are traditional AGM and not advanced AGM (spiral wound for instance) the standard lead acid profile is fine.
As mentioned though, newer chargers, newer advanced profiles.
 
Thanks for the comments!. There is a lot to learn, so this is what I found out:

Batteries need a specific "floating voltage" after fully charged.

Now, before removing the old batteries, I measured the voltage and the charger was "floating" them at 13.98V ( after several days).

An AGM battery needs to "float" at 13.5V at 25C, now yesterday's temperature in the engine room was at least 30C (conservatively...as I was sweating considerably), at this temp an AGM battery needs to float at a lower voltage, if you apply the correction factors from one manufacturer = 13.41V.

If the current charger was to apply the same floating voltage at this same temperature, my brand new (not inexpensive) batteries would be floating at the wrong voltage : 13.98 (instead of 13.41) effectively overcharging them by more than half a voltage. For flooded batteries this may be OK, but for AGM batteries this is a killer.

The AGM manufacturer's website has a very narrow floating voltage range tolerance ( 0.3V), so more than 0.5V is definitively outside this range.

Appreciate any comments, ... for now I'm inclined for the new charger!.
 
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4_Ever_Newbie said:
Now, before removing the old batteries, I measured the voltage and the charger was "floating" them at 13.98V ( after several days).
Click to expand...
This troubles me. After several days, id expect my charger to me in idle mode, thus the batteries would be at their normal static/at rest level. nearly 14V indicates the charger is still actually charging. This could be the result of a failed charger, failed battery keeping the charger in a charge mode, or parasitic draws keeping the charger in charge mode.
 
AGM batteries do best with a charger capable of temperature correction. I installed a pro-mariner 1240P when I upgraded to AGM. Has worked good for me and reasonably priced.
 
Looking at the Pronautic and Mastervolt units, the first one would be the obvious choice as is made here in USA but they don’t publish their temp compensation curves (per a 2016 amazon review they under correct and only do temp comp if float current is higher than 5A ??)...wondering if anyone has experienced issues about this. I have contacted their tech support will share here what I learn.

Mastervolt looks great but needs a special adapter and a computer to be able to configure things like charge/floating voltage ( per my Batt manufacturer different from their factory defaults)....so this looks more like a product suited for large battery banks in bigger boats.

Do you know of any other chargers using a temp probe?....

Blue Ocean had their main facility destroyed in a fire last year so not sure I want to by from them now...

Mastervolt 12/25-3

DD132BFA-6B84-44CC-AC84-E08C0CE6FD27.jpeg


Pronautic 1230p
14282AEB-ED24-4AA0-A967-E356246628EE.jpeg
 
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I installed 4 AGM group 31 batteries on my 340 last year. Original charger. Seems to work fine. When I arrive at the boat they’re typically between 13-13.3V and 100%. Charger never pushes them over 13.5.
 
M Prod said:
I installed 4 AGM group 31 batteries on my 340 last year. Original charger. Seems to work fine. When I arrive at the boat they’re typically between 13-13.3V and 100%. Charger never pushes them over 13.5.
Click to expand...
What charger?
 
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