As pointed out, an AGM battery still has distilled water and acid mix, but unlike a wet battery where the fluid is free to slosh around, the mat's in the AGM contains the fluid to keep it from sloshing instead.

Normally on a sealed AGM battery, the matts are thick enough, and enough fluid added to full saturate them, but seems that on some of brands that only have a 6 month warrenty, not enough fluid is being added to fully saturate the mats, and why you end up with dry cells in them so quickly (within a year or two). My Die hard AGM battery was one of them, cells went dry about the 1 year mark, and by adding distilled water back to the battery mat's, the battery is on it 4 year and still going strong.

So on a AGM battery that is only a few years from initial filling of use will not take/hold a full charge, then pop the caps, add in the 20CC of distilled water to each cell to re-saturate the matts again, and will get many more years out of the battery until its the plates that gives up the ghost instead.

As for why batteries come pre fluid now in the states, It was a EPA thing. Instead, wish the AGM batteries did not fluid filled yet across the board, since clock on the plates does not start until the fluid is adding to begin with, plus give you ports to open the battery back up with ease, to add more distilled water if needed if the to the mat's go dry before the plates give up the Ghost..


And why I showed the video, it shows you the port locations of where the battery was original acid/water filled to start with,and what caps will pull off to get the ports back open again. Hence battery will have the fill ports, and will have the vent ports. Do not screw around with the vent ports, and only use the fill ports to fully re-saturate the mats with the distilled water.

 

I just bought a Die Hard for my UTV from Advanced Auto store a couple days ago. The box had a dry battery, and a bottle of acid. I had to fill myself, it didn't requre a charge.