I got some really interesting info from the latest edition of the
Jaguar World magazine today (April 2016).

The Jaguar World Technical Advice service (pg -100) states that the
correct battery type for the 1992 - 1996 4.0L XJS is a Type 096.
Some parts suppliers mistakenly say it is a type 017 which is Wrong !
By the way the 1988 - 1991 XJS battery is a type 075.

The article also states that with the ignition in the "OFF" position the
battery current draw should be 0.1 Amps due to the requirement
that the trip computer/clock, radio and alarm system be powered on during
the ignition "OFF" state.
The Advance Auto parts store I used gave me a AutoCraft battery ($159.00)
with the specs:
Group Size 47H5 with 590 Cold Cranking Amps (CCA) below 32F,
810 CA above 32F. The same size battery was recommended for the
V12 6.0L engine.

No type 096 Battery was found. Maybe the battery world has changed the
sizing and usage nomenclature?
The 47 is a group size (US) and the H5 is a DIN size (Euro market?).

The amp/hr rating is 54 amp/hr / 0.1amps= 540hrs / 24hrs = 22.5 days
before depletion.
The battery fits in the XJS battery compartment okay.
Maybe the proper phrase is, "The fitment is correct. . ."

What I was looking for was the "OFF" ignition current draw which according
to the article should be about 0.1 Amps.
My driving habit for the XJS is about once every 4-5 days. And it cranks
with no problems if it sits that long with no battery maintainer.
So, I should be able to have it sit for up to 10 days and still have it start, maybe.
I now connect a battery maintainer to it on the 2nd day that I do not drive it. That should work for now.
I really like the Jaguar World Magazine for the info and the user comments.
I get the magazine via the "Pocketmags.com" site.
A little pricey for a yearly subscription but a lot less than the
actual magazine being sent via regular mail.
And it seems to be the only magazine out there that covers the Jaguar brand solely.

Happy Trails and P O R - Press On Regardless

 

That sounds about right, once before I got a "maintenance charger" my car had been sitting about three weeks when I went to the garage and found the alarm going off, due to the low battery. I'm not sure what the capacity of my battery is though. Now I plug it in whenever it's parked in the garage - doing it all the time makes it a lot easier to remember to unplug it before leaving.

 

Could be a UK thing. Plenty of Type 096 batteries over there...


096 Car Battery | Car Batteries | Euro Car Parts

 

I recently bought this 096 type battery (live in UK) for my 93 model 6.0 V12.
As stated earlier the supplier's guide listed the wrong size.

This advertisement lists many alternative battery models:

Yuasa 12v 80Ah 760A Silver Car Battery YBX5096 (HSB096)



Yuasa Silver car batteries allow around 50,000 engine starts, compared to around 20,000 on a normal battery.
Silver car batteries come fully charged, ready to fit and are completely maintenance free.

The YBX5096 has a built in state of charge indicator, this indicates if the battery is OK, needs a recharge or needs to be replaced.


Brand: Yuasa

Voltage : 12v
Ampere-Hour Capacity at 20hr rate Ah: 80Ah
Cold Cranking Performance (Amps) SAE/EN1: 760
Dimensions LxWxH: 278 mm x 175mm x 190mm
Terminal Layout: Negetive (-) on left, Positive (+) on right; with the terminals on the edge of the battery closest to you
Terminal: Standard Round DIN post
Alternative part numbers / can be used to replace: 096, YP096, 57412, 067, 096T, 296, 566 38, 566 038 051, 566 38, 566 047 051, 566 47, 566 047 051, 570 12, 570 409 064, 572 29, 572 029 057, 574 12, 012 068, 575 15, 577 400 078,

 

years ago, I installed a marine battery disconnect switch in the trunk because our XJS ('94 conv 6-cyl) sits for long periods. Yes, the clock and radio must be reset each time, but I always have a fresh battery for starting.

 

Yup!

I do exactly the same, I fitted a Dis Carnect Battery Isolation Switch, which I turn off every time I put the Car away, which always keeps my Battery Fresh and Starts the Car first time.

I've had enough of nice Sunny days, when I'm wanting to go out, where something like the Car Alarm has drained the Battery dry.

discarnect battery switch | eBay

 

Here is what I found regarding battery for my XJS's. Watched a video comparing batteries from Approx. $100.00 to $500.00. dozens of tests, All these fancy batteries, guess who bet them all, pretty much in every category.? Walmart's EverStart Max ! Who would of thought ! For the XJS --- Everstart, Max, 47-H5

Here is the link,

 

Wondering how that Walmart Everstart worked out for you after some time has passed? I’m considering it for my ‘91 coupe! Dimensions seem right?!

 

Just to follow-up on an old thread. Just Replaced a cheap and cheerful H5 from the PO with a Diehard AGM H6 size - snugged in nicely and works a treat. Also used a Dorman battery venting kit.