Join Date: Aug 2005
Location: Orangeville, Ontario, Canada
A good glass mat and/or gel type battery, because it is not direct vent, it is vented by a check valve system built in to the side or top wall construction. Why?
In a wet cell battery the cells are vented to atmosphere to prevent the excess gases in over charging to leave the battery enclosure thus no massive amounts of high internal pressure build up.
But the AGM and or gel type battery uses an electrolyte in the form of jello or gel that is not free flowing, so there is no spill of the liquid conductor from inside the battery enclosure, but as a gel type, over charging is still possible. To keep internal pressure under control that battery uses a built in check valve that operates to remove the pressure.
Originally these gel batteries had a limit of 1 or 2 amps to charge them. That low amperage keeps gassing down, but automotive batteries give and take lots of current, thus the check valve.
The design comes from deep cell technology where these batteries are drawn down to 80% and recharge at a slower rate and have a very tough designed wall structure.