What's the best charging position for robot batteries?

[philso]

I seem to recall Enersys telling us at work that if the battery vents while upside down, it may push some of the acid out. This would be more dangerous than just venting the gasses. We use tons (literally) of the 7AHr version of the battery in our UPS' each week.

[Al Skierkiewicz]

Phil,
That is true in gel cell technology but not in AGM. The acid is "locked" into the fiberglass matrix so it is not free flowing except when the case is damaged or some other catastrophic event occurs.

[DonRotolo]

Originally Posted by Al Skierkiewicz

That is true in gel cell technology but not in AGM. The acid is "locked" into the fiberglass matrix so it is not free flowing except when the case is damaged or some other catastrophic event occurs.

Well, yes and no. The 'Glass Mat' into which the acid is 'Absorbed' can be thought of as a fiberglass sponge. Just like a sponge, if you shake it or squeeze it, liquid will drip out. In a venting situation (which is a "catastrophic event" IMHO), it is unlikely the gas will form right at the vent, so it will 'push' some of the liquid out of the 'sponge' and then it can come out of the vent.

That being said, a standard qualification test for automotive AGM batteries is to drill a series of 6 mm (~1/4") holes in the bottom of the case, and NO acid may come out at all. So yes, the acid really does stay in there most of the time.

Now that being said, charge your batteries - Gel, AGM, and conventional -upright please. Spewing acid is not a national emergency, but someone could get hurt.