A battery vent tube vents hydrogen gas to the atmosphere

When a car battery is installed in the cabin or trunk, it must have a battery vent tube

Many carmakers install the car battery in the truck, under the back seat, or inside the front fender. All lead acid car batteries create explosive hydrogen gas when charging. If the gas pressure gets too high, the battery will vent the gas to the atmosphere. That’s not a problem if the battery is located under the hood, because there’s enough air movement to render it harmless. But for batteries mounted in closed location, carmakers install a battery vent tube to route the hydrogen to the exterior so it doesn’t explode. It’s a safety issue.

Car batteries can release hydrogen gas when they’re charging, so you want it vented

Hydrogen gas is explosive. When a car battery is mounted under the hood, there’s enough airflow to dilute the gas and minimize the risk of an explosion. But when the car battery is mounted in an enclosed space, the hydrogen gas can accumulate and possibly explode. That’s why it must be vented to the exterior through the battery vent tube.

The new battery will have ports on either side

Vented batteries are designed with two vent ports; one on each end of the battery. The battery is delivered with one port plugged and the other open. This design allows the installer to

Move the red plug to the unused vent port

mount the battery in the proper orientation and use either side for venting simply by removing the plug and placing the plug on the opposite side.

How to install a vented car battery

Situate the battery in the battery tray with the posts in the proper orientation to connect to the battery cables.

Secure the battery hold down brackets/devices. Tighten until the battery doesn’t move, but do not over tighten. You only need enough torque to prevent battery movement. Over torquing the hold-down devices can crack the battery case.

Determine which vent port to use for the existing vent tube. If the port is plugged, twist the plug as you pull it out. Move the plug to the open port.

Replace the tube if it’s damaged or missing

If the battery vent tube is damaged or missing or the elbow is broken, you can purchase a replacement battery vent tube kit at any auto parts store.

I strongly recommend replacing the vent tube if yours is missing or damaged.

This Dorman brand vent tube kit is just $12 at Autozone

©, 2023 Rick Muscoplat