BU-201a: Absorbent Glass Mat (AGM) - info not very clear (sort of 12V/mobile post)

[joerossjr]

Reading up some in BU (http://batteryuniversity.com/learn/a..._glass_mat_agm) a few things I am curious about:

Advantages	Up to 5 times faster charge than with flooded technology Stands up well to cold temperature
Limitations	Sensitive to overcharging (AGM has tighter tolerances than gel)

So 5x faster charge means 50% of AH? If an FLA is best at C/10, then this means C/2 for AGM is perfectly ok? I have CTEK D250SA and the max I it can put out is 20A right now.

"A charge to 2.40V/cell (and higher) is fine;" which is 14.4... what's the highest? With the CTEK I see it putting out over 15V to the battery (100AH) when I first start out on a trip. What does "over-charging" consist of then? I understood that to mean during float only. Since that 15V is applied to my POS bus also... you really wouldn't want to charge at a higher voltage than that anyway I guess. Would it be best to get a buck converter to lock the voltage going to my DC fuse panel to say 12.4VDC? It's fed directly from the POS bus now.

Is a range of 10F - 120F ok? If I am ever colder or hotter than that... I won't be near the battery (in the van).

"AGM offers a depth-of-discharge of 80 percent" Is that correct? I thought it was %50 still... Not that I should ever go past 50%, just want to know.


I know these my be basic questions to you guys, but there's conflicting info on these points. Also, I read elsewhere that there's no charge input limit, so I need to reconcile these "facts".
Thanks!

[Mike90250]

Those were "generalizations" and not fact for every model of battery.

When batteries are low, they can accept a tremendous amount of charge, but as they fill up, you need to taper the charge off, especially with sealed batteries

Sealed batteries are easily damaged with wrong charge voltage