All the AGM/SLA batteries I have been exposed to have vents. Since most of the ones I have experience with are for smaller sized (alarm systems, UPS's, vehicle jump boxes), I have none with car/vehicle sized overpriced units. On these AGM/SLA's the (vents) are usually UNDER a glues label, glued cover, or a combination of both. Every larger battery I have come across (wet cells) have had only two types of vents. Those with access to the electrolyte, and those that are 'maintenance free' that you have to find a way to access the electrolyte. On wet cells, I access the cells to insure the acid is at its level above the cell plates and below the maximum fill level. IF there is no way to tell its max level, I just insure there is enough in the cell to cover the plates (and check occasionally). I do not recommend anyone open these batteries (AGM/SLA/WetCell) as you can get burned by acid. I do on my wet cells because I have had brand new batteries low on electrolyte right out of the store (bad QC, or wanting to sell more after they prematurely degrade?). Finally, many people handling/buying small/medium consumer vehicle batteries tend to not know or care what is in them or how they work, let alone how to maximize their lifespan.

Lets hope the post here doesn't encourage anyone to damage their car by trying to break a record OR think their battery can last as long, or longer. Like any link of a chain, the weakest link might be an expensive module (and we all know these parts can be very hard to come by).

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