Hi everyone:

We bought a 1999 XK8 a couple of years ago. Today, I needed to recharge the battery and notice that the vent line was just dangling on the floor of the trunk. I searched and searched and could not find where this line was supposed to vent. There appears to be a gromit on the front right corner of the floor that may be it. Looking from the back to front, it's at 2 o'clock about 4 or 5 inches from the right front corner of the battery. Could this be it? If not, where should I look. Thanks

Thom

 

This must be an American thing going back to when batteies needed topping up as they gassed when charged . All UK batteries have a small vent at each end..just a hole. If that grommet goes to outside not into the chassis you would need to extend the pipe but acid blowing up over the underside does not sound good.. Normally nothing comes out the pipe its more a pressure release as there is a complex system in the battery to prevent electrolyte escape .If there has been no acid damage to the floor I would just put it in a plastic container and forget it. ( or a plastic bag with a zip tie)

 

All XK8's were originally fitted with a vented "wet" battery. The LH vent is used and should have an angled outlet connected to a black acid-resistant tube which vents through a grommeted hole in the luggage compartment floor. Here's the vent on my 2006 XK8 - earlier years were similar:




Graham

 

It is most probable that the makers were concerned about the build-up of gasses in the boot /trunk which could be ignited by a smoker opening the boot.. Modern batteries have no vent pipe and don't gas unless charged over 14.4v. I note mod your battery has top up screw stoppers which you dont normally get in 2021

 

Thanks for the comments.

I was able to confirm the 1" to 1 1/2" grommet with the small in the center was the vent outlet. Finding the parts to make up the missing pieces of the vent line assembly was a bit more challenging. The L fitting and tube that I found in the trunk well fit the battery's front vent port and ran to the exit. To vent the rear battery port, I needed another L fitting, a T filling and about 3 feet of hose. With two stops at different parts stores, I had what I needed.

To make up the new assembly, I did the following:

• I removed the battery hold down bracket
• With the original tube's L fitting in the front battery vent port, I cut the original tube about 1" past the end of the battery
• Next, I attached the other end to the cut line to open end of the top of the T fitting and then inserted open end of the original line out through the grommet port
• Then to the remaining open end of the T, I attached the new line, ran it parallel along the side of the battery around the corner to the battery's rear vent port.
• I then cut new line to length while leaving a reasonable amount of slack.
• Next, I attached open end of the long tub to the new L fitting and inserted the L fitting into the battery's rear vent port
• Lastly, I reinstalled the battery hold down bracket.

To Graham's post, the fix described above is for those batteries where the blanking plugs are already removed / missing. Thanks for the tip on the AGM batteries.

 

Wet batteries have a LEFT and a RIGHT vent outlet. On delivery, both sides have blanking plugs fitted. For the Jaguar, remove the LEFT blanking plug and fit the vent elbow. Connect the elbow to the black vent tube. Leave the RIGHT blanking plug alone.

Here is my current (2015MY XK) showing the vent (LEFT arrowed in yellow) and the blanking plug (RIGHT arrowed in blue) on a 2021 OE specification battery. Different model but the principle is the same for the earlier XK8.




JLR recommendation is NOT to use AGM batteries on vehicles originally fitted with wet batteries. Although AGM are sealed and don't require venting, the alternator fitted to the vehicle is not compatible.

Graham

 

Graham, that little statement is going to be a bit of a sticky wicket for a bunch of us.
So far no issue with the AGM, but it looks like something we need to pay attention too.
Thanks.

 

Hydrogen gas and a relay can make quite a 'bang'!

 

unvented battery = corrosion central

explosions are rare

i think a woman and her kid died in a cayenne after they put an unvented battery under the driver seat and hydrogen sulfide built up

 

I for one am very curious regarding the basis for a compatibility warning.

There must be hundreds of thousands of vehicles which originally used the vented “wet” batteries and are now using AGM batteries, but still have the original or original “type” of alternator.

Is there something unique about the Jaguar XK’s alternator that sets it apart from other vehicles charging systems as it related to using the AGM batteries ???


My AGM was purchased when I bought the XKR 3.5 years ago. And it replaced another AGM which was installed 2 owners previous, and in use for well over ten years. My AMG timeline is likely insignificantly short compared to others.

The service history of my car is surprisingly complete and looks like the original alternator is still in place.

Are there any links to service bulletins on this issue ? Would make for interesting reading.


Z

PS Reading on jagforums.com on other (non X-100) models does reveal that Jaguar is advising not to use the AGM’s (where not fitted originally) seemingly based on the maximum safe charging rate of the AGM’s being 14.8v.

Are our cars charging higher than that ?

I have a continuous meter installed, it’s never indicated higher than 14.5v. Most of the time it’s in the mid to high 13’s. Occasionally low 14’s.


Normal ??


Z

 

I installed my current Bosch AGM battery on July 4, 2018. It is vented just as the previous wet-cell batteries have been. I went with an AGM battery because I believed my existing wet-cell battery was failing after only a couple of years. Actually, my factory alternator was beginning to fail and I did not realize it until just over a week later....

My factory alternator was refurbished on July 19, 2018 because it finally failed completely....

No issues with either the AGM battery or the alternator since....

 

I fitted a Varta AGM battery to my XKR back in 2011 when the original Jaguar battery failed and never had any problems with it, because of this I saw no reason not to fit another AGM battery this year - this time an Exide.

So from personal experience I would say there is no problem fitting an X100 with an AGM battery.

 

I have no doubt that is true. Many members have fitted AGM as replacement for the original wet battery and have had no problems. What I stated above is the JLR recommendation (battery care instructions) to replace like with like:





JLR issue numerous recommendations and procedural instructions in manuals and bulletins. Dealers are obliged to follow these but owners can choose ignore any or all of them.

However, the thread is Location of Battery Vent Hole which does not apply with AGM and this is a diversion from the topic.

Graham

 

Not entirely true, both of my AGM batteries have stated that in the case of a charging or other fault causing a pressure build up they will vent through the hole, that after all is the reason they are still fitted.

So if the OP, and any other interested owner, has an AGM battery fitted they still need to follow the previous helpful posts and to make sure that the vent tube is correctly fitted to their battery.

 

Modern batteries have a vent hole left and right ...each one vents 3 cells so just using the left hand is a bit pointless. mIne is a 97 and no sign of acid attack under the battery and no sign of the grommets having being used.

 

My car's battery was missing both the vent tube as well as the vent plugs when I bought the car. I purchased a vent tube 90 degree connector, plug, and tube from a salvage yard and installed them in the trunk. The end of the vent tube goes through a grommeted hole in the right rear corner of the trunk. There is a vacuum coupler (straight connector) that fits into the grommet and vents any gasses outside the trunk.

Gases are usually produced when the battery is charged from the alternator (as well as from a battery charger). My '02 Thunderbird also has a trunk mounted battery with a vent tube. When replacing the Tbird battery the auto parts store made a stink about the vent tube. The gases can explode but I think the bigger issue is that the gases vent into the trunk which is considered part of the passenger compartment. The gases can lead to health problems if enough gas builds up inside the car. Since the passenger compartment is relatively well sealed from the outside dissipating the gases is essential. From a safety perspective you are well advised to make sure the positive end of the battery is vented through the tube and out under the car. For the vent to be effective you must also plug the hole at the negative end or the gases can still vent into the trunk. (Or you can use two 90 degree connectors and a vacuum "tee" and vent both sides out under the car).

If you want a picture of the vent side of the battery, including the tube and grommet, send a PM and I'll get one for you.

 

All batteries in all markets are vented to the outside for this car and any other where the battery is inside a sealed compartment. Outside of a very few brands of batteries, even AGMs vent H2 gas among other things. Even the "unvented" batteries have an emergency relief.

The way that the vent tube installs keeps any corrosive gas away from the metal of the car. The tube should have a band of red tape showing how far to insert it into the frame hole grommet. Next, most batteries in my market come with both right and left vent holes OPEN and a kit for installing them taped to the side. This kit always has a plug for one vent for situations such as our cars. The battery venting is contiguous, thus two ports are redundant. If one hole is not plugged, the pressure might more easily escape into the boot. Next point.

The force of a H2 explosion is unbelievable with very small amounts of the gas collecting. Actually it works even better with less gas. I have seen battery cases shattered and a Corvette hood blown open when an owner's battery maintainer failed and boiled the battery. Said owner not realizing what happened, unplugged the tender and went to start the car for a run. Whatever made a spark in the engine compartment was enough. This is a modern version, probably 2012 or later. Acid everywhere, cracked hood, burnt wires and a nice insurance claim. Just imagine if he decided to open the hood to look around before starting it and something electrical clicked. Last that i checked, the boot on our cars is electrically activated. Want to go there? Or, how about the CD player and amplifier? Hope that you like booming bass.

As for the charging circuit thing with AGMs. In many cars with lead acid batteries and overall good engineering it is known that if the battery is too discharged the alternator cannot get it to full saturation which has long term implications. Essentially the alternator cannot recondition it. This is rather commonly known even with long road trips. Lead acid batteries are not meant to be discharged. AGMs are actually more forgiving of this but are the same chemistry. The alternator in our cars and most others cannot recondition a flooded battery let alone an AGM, and either situation might make it work harder. Using a tender when it is low or for extended storage solves this for any battery. If one runs the battery down a little which is easily avoided, simply recondition it. Done.

And, always make sure the venting is setup properly and do not use a cheap battery tender. The boom described above was so loud that someone rightfully called the police. You like not being blind and having your body mostly intact?

 

Utter rubbish!! Where did you get that misinformation from ? Or are you just guessing ?!
Are you claiming Jaguar was incompetent when they only used one vent when installing the original battery ?

Varta, Bosch and Exide information: Only one vent connection on the battery is needed - plug the one on the opposite end as described.

Simple test - if you blow through the vent on one side of the battery, with the other vent unplugged, the air travels through and comes out the other side.
Just tested it on my Varta and Exide AGM batteries.


Why you should always fit the vent tube:
VRLA (valve regulated lead-acid) batteries. In normal use, any gas evolved during charging is recombined inside the battery so no vent is needed, and no water is lost. Under fault conditions (most likely faulty charging system or possible short circuit), gas can be produced at too high a rate causing the pressure inside the battery to rise, in which event a pressure relief valve opens and vents the gas out through the little tube to stop the whole thing exploding. In the case of high charging voltage this is likely to be hydrogen (explosive in low concentrations), and in the case of short circuit or internal fault it could be steam and/or hot acid (generally nasty and unpleasant).

 

Yep, you vent one side and plug the other. As long as you follow those instructions you are good to go....

 

In 40 years as an auto electrician I have cut open many so called sealed batteries to top up the elctrolyte and I can assure you not all are linked. Maybe ones specifically for XK 8 are but many generic ones are often not ...