Have known the battery/compartment in the rear mounted Jags need to be vented, but have never found anyone's resolve to this, so I just configured it as I believe it should be. I basically Tee-d at the fwd vent hole of the battery with a vacuum Tee and out through the boot/grommet in the bottom of the trunk compartment fwd of the battery. I used white automotive vacuum connectors that tapped snuggly into the battery vent holes. There is a vent hole on either end of these size batteries for this install. So here is what I've done, and hoping some chime-ins if anyone knows better or sees an issue... here are some pics of the install:

 

Hi Steven,

Your installation may be fine. On our '93, the original battery had only on vent hole, to which was mounted an L fitting rather than a T. The L connected to the vent in the battery, and a rubber hose connected to the other end of the L and ran straight down through the floor of the trunk/boot, which was lined with a rubber grommet. You really don't need a T with two hoses attached - either an L or straight fitting with one hose is sufficient.

Newer batteries with two vents often have plastic plugs in the vents and you have to remove the plug from the end you use for venting, so you may want to be sure that both of your vents aren't plugged.

Also, the routing of the hose to the underside of the vehicle is somewhat important because the acid fumes escaping from the hose can rust components on the underside of your car. On our '93, for example the hose emerges a little behind the differential, and when I rebuilt the diff I noticed that all the diff cover screws were well-rusted. I added a longer vent hose to get the fumes further away from the diff and into the air stream beneath the car to be carried away.

Hope this info is helpful. I'll look forward to seeing what others have to say.

Cheers,

Don

 

I can't type today. The original battery on our '93 had "one" vent hole....

Also, your post has prompted me to check the setup on our '04 XJR, which also has a trunk-mounted battery.

 

Looks good sjc. My batteries are vented on one side only, nearest the single vent hose. That leads me to assume that ALL the cells are vented from one side (I hope). But, you can't go wrong with two vent hoses!

 

My new battery has twin vent holes and did a similar setup.

 

What's the failure mode if you happen to have fitted a brand new Bosch 019 battery but forgot to fit the vent hose...

 

there's no failure code. I'd been driving the last couple years without the ventilation tubes installed when I came across a thread in here regarding it. Vehicals with under front hood batteries installed dont have ventilation issues because they are in the open air if any gases should escape, but in the rear trunk/boot mounted Jag batteries the gases dont have anywhere to escape and therefor have the potential to cause explosion, fire, noxious fumes etc. I havent heard of any instances in which this has happened, but it makes sense they should vent to outside of the vehical, and original manufacture sent the cars off the line this way Im sure. Ive vented mine accordingly because its an extra safety precaution, and Im retro ****! I prefer things to look and function properly.

 

thank you all for all the replies and insights. makes sense only one side would need to be vented, the battery came with 2 vent plugs. sounds like factory original was only one vent line. dont know if 2 matters or not. I appreciate the rust issues Don B presented. I think I'll ensure mine is not venting out onto crucial parts and fasteners also. Rust on a Jag is not good! on any car, but especially the Cats!