Battery Vent Plug Installation

Absorbed Glass Mat (AGM) and flooded lead acid batteries can produce a number of potentially dangerous gases, which requires that the battery be properly vented on vehicle applications that have the battery installed inside the passenger compartment. The typical maintenance-free battery is completely sealed except for two small vent ports in the side. These vent ports allow the gas that is produced in the battery to escape.


On applications with a single vent tube, the opposing vent opening on the battery cover must be plugged using the vent plug.


Batteries that require venting include a removable vent plug, which can be inserted into the vent port that is opposite of the vent hose that leads to outside the vehicle. The twist-off plug is attached to the positive terminal cap. (Fig. 15)


Fig. 15


Instructions for using the vent plug are included on the battery positive post cover. (Fig. 16) Press fit the vent plug into the battery to ensure proper seating into the vent port. (Fig. 17) Be sure to never plug both vent ports.


Fig. 16


TIP: Some batteries may have vent hose configurations that vent both ports to outside the vehicle, such as the Saturn Ion. These applications do not require a plug.


Fig. 17


– Thanks to John Munsell

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