Nofear

Hi Bob,
Thanks for confirming...
Are those batteries on a UPS tray what is referred to as the low hanging fruits?

With the batteries that I have dealt with, the only time I experienced that whoosh sound from opening a stuck one way valve is when the cell is actually below atmospheric pressure. I could see the walls being sucked in and they go straight back again after the air is let in.

I am presently working with 200Ah marine AGM batteries and I made the mistake to go to 15+V. I got some serious bubbling and the inside turned brown where it was a nice white until then. So from now on I capping my charging to 14V. Not sure how it is going to affect my desulfation effort if the chemistry is asking for finishing voltage beyond 15V? The adventure resumes....
Peace,
NoFear

Hi Bob,
I kind of do the same thing, but you seem to be more gentle on your batteries then I am I want to mention something in my experience dealing with battery rejuvenation and see what is your approach.

I get batteries for free as well so I am less picky about which battery I accept to play with but so far I never had a lot of success with old "bulged" batteries. I understand that the sulfation is so thick that it is pushing the plates apart and end up pushing the plastic casing out of shape. I am always hopeful and thinking giving those battery a chance but it always end up being a waste of time. I am starting to think that ALL bulged batteries are too far gone to even try to recover them.
Has this been also your observation?
NoFear