So after the polar vortex it's finally warm enough that I considered driving the Jag today. I know, I have such a good sense of humor. Not unexpectedly, I got...nothing. Put the key in (I did still have a door chime, oddly) and not even a small effort.


Given that she's not run in a long while, and it's been record breaking cold, I'm figuring the battery is gone for. My new best friend (aka my Jag mechanic) doesn't like keeping flat batteries in the car, so he suggests taking it out, bringing it up for testing and either charging or replacing it.


Now, given this IS a Jag - are there any little traps or tricks to actually removing the battery? The cover in the trunk/boot is off, I'm guessing the brownish red is the positive? But once I remove the plastic covers and cables (negative first, I know) are there any other fiddly bits to worry about?


Thanks in advance - where I come from originally (NJ) we don't even pump our own gas so Jag ownership always brings something new for me to learn ;-).

 

polarity is usually marked on the battery next to the post on the case somewhere

 

Why not charge it in situ and see if it's still good? Buy yourself a battery tender to keep it from going flat again.

 

I keep battery tenders on all my collector cars that I do not drive on a regular basis.

 

What's a battery tender? Does it need to be plugged in?

 

A battery tender is a smart electronic device that will perform two duties: charge the battery and keep it charged at a desired level. First, it will charge the battery at a rate that may take from hours to days, depending on how low the battery was to begin with (or how expensive the battery tender is). Second, it will keep the charge by constantly monitoring and detecting any existing slow discharge then re-charging, as necessary. That's what the one I have does and I paid only like $30.00 for it, so it's kind of a light duty device and, as such, it will not start the car, but it charges and maintains, as advertised. Of course, I do have a 30 year old Sears starter/heavy duty charger with wheels... that I seldom use anymore, since I got the battery tender.

My battery tender monitors and displays via LED indicators. Basically, if the battery has damaged cells (either less than 10 volts across or a very limited/erratic charge rate) it will give you the bad news LED, otherwise an amber LED for "charging" and then a green LED for "battery fully charged".

Nowadays they have heavy duty, fairly portable devices that will also start the car from an internal source (a battery, or a nasty big capacitor? dunno) for when no AC wall plugs are available. They're not cheap, so I would imagine that they can also maintain the charge, like the cheaper little batt tenders do, because if they do, that would make them the ideal device to have with you. Just the other day, this yellow Lambo next to my XJS at the car show wouldn't start (slow to no-crank) and somebody came with this portable device with cables: no-prob...started right up. I should just get one of those, you never know, just need to find one on sale...

 

Yes, the battery tender needs power from an AC outlet.
Also, once the "batt fully charged" monitor lights up, you can keep the tender connected for as long as you need; that is what it does best. It's really nice to be "re-assured" of a ready-to-go battery every time you walk by it and see the "charged" LED is ON....

 

I have one of these units, and they won't work as a battery tender. Just good for a boost and that's it. They go flat just like regular batteries.

 

So, pretty much like carrying a spare battery... to where no AC outlets are available.
Basically, it is the battery tender what's a must, especially for cars that are not driven daily...and you can always use jumper cables along with your other car.

Cheers,

 

Thanks, gang! Sadly, I don't have electric near the car, so the battery tender is out. But good to know about. I did pull the battery - damn that thing is DENSE! - so as soon as I get it checked and hopefully charged, we'll see if it was indeed the problem.

 

Gina,

If you are not going to drive the car much during the winter, I'd recommend keeping the battery out of the car and inside somewhere where you can leave it attached to a tender. Cold temps and the quiescent current drain will often make the battery unusable in a week or two of dormancy.

Be careful if you jump start the car, they have a tendency to fry the battery or ECM

 

I was actually pondering doing just that. I'm thinking that may be why my mechanic was not in favor of a jump start, either. I may be putting it in to test and taking it right back out!

 

I use a battery tender on the 94 XJS and I am considering putting an external access attachment wire set for the 99 VDP now that I have located the 99's battery firewall attachment points.
To wire up a battery maintainer cable access point will require some experience with
electrical wiring and wiring tools.
Otherwise you will have to access the battery in the boot or the access points on the engine firewall with the battery charger battery clips.
I do not recommend charging a battery at a 2+ AMP charge while it is in the cars
circuit. Disconnect the Ground (-) cable from the battery when using a high AMP charge.
You could damage the engine management electronics or the battery charger if there is a short in the car wiring. I've had to replace the Alternator on the 94 due to a bad battery
and I don't want to repeat the experience.
Once the battery is charged, then connect it to a battery maintainer

I wired up the 94 XJS using the +12VDC engine firewall connection and the Ground
firewall connection points.
Most of the Battery tenders come with a 2-wire cable with battery clips. I cut the battery clips off and spliced "O" Lugs on and attached those to the Engine Firewall +12vdc and ground attachment points.
The actual battery maintainer connector went out the front grill so I don't have to raise the hood/bonnet every time I want to connect to the Battery Maintainer.
I set the Battery Maintainer on the Hood of the car as a visual reminder that it is plugged in and it has to be removed before moving the XJS.
It has worked great for the last 2 years and no more flat batteries.
My rule of thumb for car batteries is a 3-5 year life span. You can expect problems at the 3 year point and the 90% probability of total failure at 5+ years for the typical user.
The battery maintainer does improve those time lines and odds.
I haven't tried the AGM (Glass mat) batteries yet. More $$$.

 

For access I go through my cigar lighter, but I had the convenience of having rewired it to "always hot" for my engine start/stop button install (8-gauge wire and a new, dedicated 5A fuse on the firewall). Just plug it in and that's that. My tender's max charge rate is 1.5 amp.

You'd be surprised from how low a battery charge status these tenders can bring the battery back up alive. I've seen it charging for more than three entire days and, finally, the green light!!

For those cases where no ac wall plug is available, I'd say that a nice battery switch would be the next thing, short of bringing the battery indoors... Some pretty nice ones from $25 to $50.

Cheers,