I was at the local Interstate store a couple of weeks ago and they didn't have the AGM in stock for the XJ8, didn't know when they'd get any due to supply chain issues. Thus I went elsewhere and bought a Duracell AGM. I really wanted the Interstate AGM because I'd bought one for the XF previously and knew that it was absolutely identical to the OEM Varta. I kind of wonder if they "recommended" the standard battery to the OP because that's all they had in stock. Classic car owners have been switching over to AGM batteries because at least theoretically they supposedly last longer in the typical use case of long term storage and short trips. I'd been getting 7 to 9 years out of a standard battery kept on a maintainer so I'll be looking to see is these AGMs go more than nine. But I've also had a standard lead-acid battery explode on me before . Although rare, the AGMs are also supposed to be less likely to do that and so that's partly my motivation for spending the extra money. I've got four out of five switched over to AGM so far in recent years so check back with me in about ten years and maybe by then I'll know if it was worth it.

 

Z,
I'm completely agnostic on the wet v AGM subject. The theory stated above explains why you shouldn't, but many are reporting that, in practice, they work just fine.

Perhaps I was a little unfair to Jaguar. If the AGM isn't theoretically a direct replacement for the wet type orginally fitted to the X100 without some modification to the charging regime, then the dealerships will understandably follow the guidance from mission control.

 

I added the brief technical explanation because several member have been dogmatic in their insistance that AGM is a direct replacement for wet. As with many advances, there are other factors at play and we cannot allow an opinion which is technically inaccurate to go unchallenged. This being said, I have seen no evidence or reports that AGM has ever caused a problem when paired with an earlier generation alternator.

Worth adding whilst on the battery specification topic is JLR recommendation for their stop/start models is they MUST be fitted with AGM.

Graham

 

you are obviously referring to my posts.

First of all, I never used the words to the effect that the AGM’s were a “direct replacement” or “technically correct”. I did literally say my experiences are anecdotal in nature and not to be taken as any type of scientific study.

As a result of my direct observations I point out that the AGM’s simply work, and work much better, last longer, and with no maintenance required.


it’s more than a stretch to label my comments as “dogmatic”. What a snobbish slur ! I expected better from you; as least a more elegant put down.


Z

 

I was referring to numerous posts on this same topic across all the model forums. Your individual post was not in my mind.

Whenever it becomes necessary to single out an individual member over the content of their post, I make use of a forum Private Message and not a public rebuke.

Graham

 

I have a 2007 XJ8, the battery was dead. Advanced Auto wanted $240 for a 3 year battery. I called the dealer and got a 5 year battery for $250. Better check with your local dealer first.

 

Keep the power hot as you change the battery, I did not do that, and it took me two years and thousands of dollars to get my catalytic converters to complete their cycle!

 

I have a 2000 XK8 coupe. Bought my replacement battery at Walmart, it was the least expensive by far. Took me about 10 minutes to change it out myself.

 

What cost thousands of dollars?

 

I changed mine out by removing the old battery then immediately installing the new one. No problem with the cats. BTW, there is a specific drive pattern required to reset the cats. The info is readily available on Google. It is a weird pattern, but easily doable yourself.

 

I don't know much about the newer models, but on my '98 and '99s the cigar lighter is dead when the key is off, so a trickle charge there won't work when changing batteries. I'd suggest just checking voltage in the lighter socket with key off before committing to this course of action.

 

I'll throw in my latest experience. I'm working to get my 2006 XKR back on the road with some suspension work. The car has been sitting for some time and I had to take the battery out of the vehicle to charge it. Initially I had some codes flagging that I was not familiar with, came back to the forum, realized it was a battery issue, charge the battery, and no problem since then. However, during a blazing hot 98°F day in Chicago, caught in rush-hour traffic, air conditioning on high, I watched the voltage change from around 14-14.1 down to approximately 12.2. That's when everything stopped. The car quit. I was able to restart it and barely get off the road. I waited approximately five minutes, turned the air conditioning off, and restart the car where it started to charge and show approximately 14 V (I have a device connected to the OBD port to monitor coolant temperature and voltage). Note to self, time to change the battery. Thank you for all of the information and opinions regarding this matter. I did have to reset the Windows by the way. Just an FYI
Robert

 

Went with H8 - AGM Interstate battery for $250 with 3 year replacement warranty. Install took under 15 minutes during which they maintained auxiliary battery power to the car’s settings so no disruption. These are not prorated after 3 years unlike the non AGM battery. I weighed the pros and cons and AGM is the way to go.

 

Hi David,
Thanks for helpful post. How did they maintain auxiliary battery power? Did they use a battery charger? Would one of those battery jump chargers work?
Sorry, just curious.

Thanks,
Norm

 

New to the forum. What device do you speak of and where can i get one?

 

Same question about the auxiliary battery power.