AGM = Absorbed Glass Mat.
Basically a more refined version of the conventional lead-acid battery.
Has a similar kind of lead plates, separated by a fiberGlass Mat which Absorbs the sulphuric acid elecrolyte.
Sometimes this plate/glass mat sandwich is wound in a spiral, like in Optima batteries.

They work in the same way as conventional (called 'flooded') lead acid batteries, but need a slightly different recharging profile for best efficiency.

Advantages:
- sealed and don't leak, can be mounted inverted...
- can accept a larger charging current
- lower 'self-discharge' rate (ie if left unused they hold a charge longer)

Disadvantes:
- more expensive (maybe 25% more)
- harder to find...

For all those reasons, they're a much better solution for an infrequently used car, or one in a hot environment.

Hope this helps.
Jeremy

(Ask an Engineer the time, and he'll tell you how a watch works...)

 

I also had to replace the battery in my 06 as it still had the OEM and it was really about 8 yrs old, the car was built in 05. Interstate Batteries has the replacement battery and they will R & R for free. They have an adapter they plug into the lighter socket that keeps power to the car so reset is not a problem. I found out many high end cars use that same battery. After I had that done I had several beers to sooth the cost of $260.00. I think the dealer was around $400.00 to do the same service. Good Luck

 

Thanks to all on this thread. I had my 08 XKR LCD screen freeze on the Jaguar logo, no music, etc. Found this thread, did some troubleshooting by installing a trickle charger, which unfroze my screen. Decided to get an AGR battery, even though my battery tested OK. I had to convince Interstate Battery to get an AGR (MT5-49/H8). Also had a bit of difficulty getting the proper vent adapter and plug, but Interstate was able to find them from a recycled battery. So far, there have been no repeats of electronic trouble.

 

Sears and Advance Auto also now carry AGM batteries that fit the XK at a very reasonable price. (Note the online Sears cross reference says it does not fit, but that it is incorrect.)

 

JeremyB perfect answer and I am an engineer! I am familiar with Optima batteries for boats, not used every day etc. So for a vehicle that is driven regularly, a traditional battery may be fine?

WhiteXKR good info on Advance Auto

thanks your responses
RyeJag

 

The problem we found with several that "drive every day" is that the time/distance was quite small. This was still a problem, as the battery never had time to recover and they too had repeated problems.

With an AGM, charging rates are theoretically about 5 times faster, so they are much quicker at recovering over a short drives.

I dont swear the AGM is our "failing battery" answer, but several of us bailed on the OEM battery and went AGM, and I have not heard of a battery problem from any of them since. Most are still under a year since the swap, so only time will tell if our choice was really the right one.
More food for the thinking....thought... errr...brain thing.

Vince

 

>> I am familiar with Optima batteries for boats, not used every day etc.

Thanks for the Peer Compliment ! Regrettably, Optima do not make a Group 49 (the battery industry sizing name for our batteries) battery - I asked them directly !

And another point - for any cars still under warrantee. There is a Jaguar TSB (attached) that instructs the Dealers to replace type-for-type.
Personally, I think AGMs are the way to go (at least until Lithium Ion gets more affordable). There's no reason I can see not to upgrade, but the Dealers are probably constrained in what they can do.....

 

JeremyB,
For the majority of people a group 49 conventional battery plus a 3 stage charger( a must) is the way to go.
If you want to do aerobatics us an AGM and for LOW power applications Li Ion is fine but store in a metal box if possible, I do!.
Between my Boat, Motor Home and cars I have 10 batteries all conventional; got 13 years out of my 6V boat house batts (Trojan, deep cycle golf cart!).

A retired Boeing Engineer,
Adrian

 

So many engineers drive XKs. Who knew!

(I am an engineer, too...)

 

Vince et al,
Interstate shows MTP-93 850 cca's for 2007 XK's NOT the 49/H8 which the Dealers (mine incld.) install; 6.88 x 14.38 x 6.88, much confusion as usual.
WalMart carries the H8 for $120 but may not have a vent! and 760 cca's made by Johnson Controls (USA?)
Jaguars are always such fun; only had them for 53 yrs ...........

Please Fly your flag today, Adrian

 

Flag is out!
Don't understand your question Adrian... Are you saying the AGM battery I have in my car does not fit?

I made a call to Interstate tech support and asked for an AGM battery to fit my car. They informed me the MTP-49/H8A (A for AGM) would be the one I need. We then learned that the part number given has since been replaced with a newer part number MT5-49/H8. Both numbers are the same battery.

Note: If you buy the plain MTP-49/H8, (without the A suffix) you are not getting an AGM battery.

Does that help?
Vince

 

I recently installed the Walmart H8 batt in my XK. What is the problem with the vent??

 

Vince,
No,I didn't say so or know about the AGM. Just wanted to make point that the MTP 93 has more cca's than the 49/H8 for a similar size.
Don't know why every body seems to fit 49/H8's; next time will use a MTP 93, hope it is refillable ! My Interstate 49 is not and made in CK!!
Next time at WalMart will look at their H8 for a vent, where it's made and is it topable.

Adrian

 

Next time I need to get one, I'll probably get an Odyssey. It's a bit lighter with about the same CCA.

 

I have had some of the issues discussed and believe its time for a new battery. Will dealers put an AGM battery in or do I have to do it. Where do I get the vent and how to install it?

 

Just ordered one - doesn't seem very light at 60lbs but I've read nothing but good things about them.

 

Another question on batteries. What percentage charge should a healthy battery be at after a good amount of driving in a day. I drove about 35 miles today and when I came home, I put my Shumacher charger on and the indicator showed that the battery was 64% charged. It took only about an hour to bring it up to 100%, but what is normal? Is this a sign that my battery is declining?

 

Its pretty hard to say how much driving is needed to 'recover' the battery, as it depends on the initial charge state, what electrical accessories you were using etc.
However, in general, the more charge put in a battery, the higher the internal voltage gets, and the harder it is to 'push' charge into it. So, charging the last 20% typically takes waaay longer that the rest.
(on liveaboard boats, the batteries are typically charged to 80%, then discharged down to 50% as that offers the most efficient profile).

So - I wouldn't be concerned - it only took an hour to top-off the charge. If you're still concerned a 'load test' is the only real proof.
OEM rating is 850Ah, mine is down to 770Ah after 1 year.

Lstford asked:
>>
I have had some of the issues discussed and believe its time for a new battery. Will dealers put an AGM battery in or do I have to do it. Where do I get the vent and how to install it?
<<
Maybe they will, but there's an official Jag Service advisory to replace like-with-like, so maybe they won't.

As far as the vent, that should already be there for the OEM battery. Its just a question of connecting/adapting it to the new one.

 

Jeremy, it was colder than Michelle O's eyes here today, so I had the heater on, the seat heaters, even the steering wheel heater for a while. I'm pushing the limit on driving the car this late into the year, but as long as there's no snow on the ground, I hate to leave it in the garage and climb into that Lexus clunker. After today, it will have the maintainer on full time. I think the battery is ok. It just struck me as odd that it could discharge so much with the car running.

Thanks for your insight.

 

Thanks for the post. I needed to hear about how easy this was going to be. I have a 2006 XK8 Convertible in my garage. I purchased it in 2008, and the battery has never been replaced. Normally, I take it out enough that I do not have a problem starting it, but this winter and my divorce were a little rough, so I decided to drive my 4WD truck. Well, needless to say, the battery in the jag is dead, and after 30 minutes of attempting to charge it all I got in return was a few seconds of dash control lights - all just to tell me it wasn't going to start. So, I am going to purchase a new battery (AGM Platinum) to replace it. Frankly, I am more concerned about the weight of the battery when attempting to remove it and install the new one, plus what if I install it and it still doesn't start? Of course, there is also the fact that I have never removed or installed a battery in any vehicle before, but I can read. I think I even have the right tools. But, if there is anyone who lives anywhere near Frederick, MD that would be willing to lend a hand, I would be happy to have a few bottles of Guinness or whatever it is you drink on hand to celebrate getting my pretty jag back out of the garage this weekend. I will toast you with a glass of red wine. I would also love a recommendation for a good service mechanic in my area, for the JAG of course. I prefer to take it in for regular maintenance but I am tired of driving to Chantilly, McLean, and/or Columbia. Plus, it won't go anywhere with a dead battery right now.