Today, I'll be measuring the 1996 XJS battery tray, and will provide dimensions here. This will be helpful to some when choosing a battery. I've given the thread a search-friendly title.

I myself went over to the shop to measure, but absentmindedly measured the battery instead of the tray. That's how I know this information will be helpful. I tried to cheat by looking it up here to avoid the drive.

I've also provided a few notes below to help people on their way to making a better choice. I abuse batteries in strange ways, and have relied on them under extremely adverse conditions, so I've got a slightly broader perspective in such matters than most.

Further information:

1: Make sure it's a sealed battery, or run a vent line. Battery gasses building up in a trunk will cause corrosion and can be deadly.

2: Fancy doesn't always mean helpful. A lot of AGM batteries are picky about charging and discharging procedures. Be careful what you choose. Each technology has it's place.

There are AGM batteries that are great in most conditions, however. Keep an eye out, and do your research. Just because it's an AGM, doesn't mean it belongs in a daily driver, no matter what the part store suggests.

My personal preferences are now in this order:

Northstar

Exide

Interstate

You don't have to buy what I buy, but have a look over the product specifications and literature to compare construction and technologies.

3: Avoid combination top/side terminals, if possible, as the side terminals in that configuration can be easily damaged, commonly damaging the battery.

4: Most batteries you see on the shelves are private labels, and their manufacturers can change often. Higher end retailers, such as Batteries Plus, are able to provide up to date information in that regard.

If you just can't be bothered to find out who makes what, Sears generally uses good manufacturers.

5: Until recently, I've had six Optima batteries piled up behind the building. Most overland and serious off road enthusiasts wouldn't touch one with a ten foot pole for a thousand dollars nowadays. You have been warned.

6: You don't need the same group battery. All you need is one that fits and has the properties the vehicle requires. Just to be sure you're cool, get a battery with better specifications than the one you're replacing, or simply look up a factory replacement as a guide to the vehicle's requirements, then get a better one.

It takes a lot of juice to regularly spin a 22 foot long crankshaft occupying an engine designed in 1738. Your choice will make the difference between a frustrating two year battery and a reliable six year battery.

A good battery properly chosen can survive ten years under adverse conditions if maintained properly. Keep that in mind when you get a bit of sticker shock when shopping. You won't likely get ten years out of one, but you'll see long life if you do things properly.

7: Most importantly.

Your vehicle is only as good as your battery. It doesn't matter how nice it is, or how much power it has. If it won't start, you're stuffed. Take time to choose the right battery for your needs. Don't wait until your battery dies. Plan ahead. Know what you want to buy before you have to buy it.

You can save up along the way to get a nicer model.

Enjoy the shopping experience. Get excited about it. A battery can be as fun as a fancy exhaust.

Others may chime in with their ideas. Please do. It's good to have a nice, solid thread that can easily be found with a wealth of information available. If you want to chime in on a battery thread, make it this one.

 

You can trim the battery hold down metalwork to accomodate other types of battery.

In general modern batteries are better and stronger than their equivalent sized older varieties.

 

In 2006, I replaced the battery in my 96 XJS with an Optima Redtop 35 and the clamps furnished with this battery were a perfect fit. I haven't had any problems since. ... larry

 

This is true. One can always modify parts. Most of my cars have seen some major alterations.

Many people, however, are either incapable or unwilling to do so. Perhaps they don't have the confidence or tools. Perhaps they want to keep things stock.

Either way, it may be more simple to use a battery that fits. I haven't written the measurements down yet, but I'll get them in here soon.

This is also true. Technologies have improved, and there are some strikingly efficient models out there, both flooded and AGM.

Not all nations get equal products, however, especially in flooded designs. In other places, I've seen flooded cells based upon old designs that would blow similar technology we get here clean out of the water.

It's interesting what we don't get here.

 

Sometimes people get lucky with them.

Countless people who rely on batteries in adverse conditions have sworn off Optima for good. They drop cells as if tomorrow will never come.

Their history is a very, very long one. Most wouldn't expect this. Far from advanced, it's the oldest VRLA design, and while pretty darn decent initially, it grew into a brand scheme rather than a reliable technology.

After 2000, the quality dropped. After 2007, it became total rubbish.

Like I said, though. Sometimes you just get lucky.

 

1986 XJSC.
The battery has to be a maximum of 245mm x 175mm otherwise it will not fit.
I was inadvertently sold the wrong battery which would not fit so I thought, no bother, I'll modify the tray.
The top of the tray is held in by captive studs but you cannot get your hand underneath to release the nuts: has anybody looked under the battery tray of an XJS? I've seen less tubes in all of the Aliens films put together. What the hell do they all do?
Anyway, decided to saw of the safety mountings at the bottom of the battery to try and squeeze it in and it was all going really well until acid started dripping on my safety flip flops.
Bugger.
Bought new battery that fits.
Steve

 

I just bought a Northstar group 65 battery. Group 65 batteries are not an exact fit, but tapping down the front edges of the tray a bit allowed me to drop it in.

Such a task would be easy for nearly anyone, and doesn't ruin the looks of the tray if you take your time.

The nice thing about group 65 batteries is availability. Many very high quality batteries are available in this size, as similar groups are popular in the performance community. They are rivaled in availability only by group 34 and group 78.

Due to their size, they are able to pack more of a punch than other groups.

Having tried several batteries in my 4.0 XJS, I will suggest that you should try to get as close to 1,000CCA as possible. I do not believe the factory suggestions are adequate.

It's a tough engine to turn over.