2005 XK8.
My battery was dead so I got the trunk open using the key hole in the back and hooked up my charger. Lights effectually came on and I left the charger on it. When I came back the charger said the battery had a good charge but nothing is working? Is there a fuse I should check to see if I blew one? Where would that be? I guess I can check the negative cable attachment under the hood on the driver's side to see if it's the cable. Any suggestions?

 

Not sure what you mean about neg cable under hood. Heres what I would do:

Grab a voltmeter (aka DVM)
Probes on battery posts >12.8volts?
1 probe on + post, other on - terminal. Same reading?
Swap. Probe on - post + terminal. Same reading?

If you get a no = high corrosion identified.

Now let's check battery negative to chassis. Probe 1 on + battery, other probe on shiny metal surface in trunk area, try bolts through rear wall by tail lights. Got same 12volts reading? Yes negative cable is good.

Open hood. Find + battery post by left shock tower (ask if you don't know about this). Probe on post, other probe on 1 of the 3 identical silver shock nut/bolts. Same reading?

I can't see how you'd find 12volts under hood if absolutely nothing works. Check the 500amp fuse in + battery cable feed. Located in trunk.

Give us feedback

John

 

If the battery was not reasonably new and you left it discharged for 3+ months it would become sulphated and useless.
When you operate the starter do the dash lights go out or dont you have any . Most probable a bad battery terminal connection.
When I am not using my car I leave a 14.2v charger permanently connected via a diode. this floats the battery at 13.5v so it does not gas or sulphate . ( you get a 0.7v drop across the diode )

Those bolts under the hood and at the fuse boxes are 12v live not earth.

 

The battery is new but I left it not running for 3 months.

The cable connection I meant under the hood was the one by the left strut.

​​​​​​As I said my system is dead, that means I have no power but the battery is showing charge. Hence my question about fuses between the battery and the system.

The 500amp fuse is what I'm looking for and is what I suspect my charger shorted out. I just don't know where that is but I'll dig through my trunk area.

 

You need a long charge say 48hrs at 15v to recover the battery . The fuses you seek are on the RHS in the front corner of the trunk area where the spare wheel is . I can see no way the charger can blow a 500A fuse .
Let us know.

 

I can't either but why would the trunk lights come on and then go off later and the battery charger shows a good charge? This is going to be interesting.

 

A battery charger cannot tell you if the battery is any good. If it has an ammeter it can tell you if its charging and if it has a voltmeter what voltage it has reached ,, You want the voltmeter at 15v and the ammeter at zero. then its as charged as its going to get BUT that might only be 10% of the new capacity because you have destroyed 90% of the plates . If you have voltgage at the bolts by each fuse box ( fed by the grey wires that come from the 500A fuses) then your wiring is good.

 

Not a constructive comment, but threads such as this one merely serve to reinforce my views regarding the dangers of leaving these cars sitting unused longer than overnight.

Driving often, practically continuously, together with keeping a battery tender hooked up whenever the car is sitting overnight or longer, seem to be a proven strategy for having a trouble free car, especially where the electrical system is concerned.


Z

 

I agree - was going to "mothball" mine over the winter, but have decided on at least weekly long run, with a year old battery

 

it would be far more effective to use a battery tender as the yanks call it than pay for the petrol at £1.50 a litre . If you have a charger then put a diode in series to drop the voltage to around 13.5v and the job is done. leave it on 24/7.

 

But that just keeps the battery charged - I'm more worried about keeping the car "aired" it being a convertible and outside. Plus driving it keeps everything moving and lubricated, so hopefully no surprises in the spring. There's got to be at least one sunny, dry day every week over the winter, even in South Wales

At £1.50 a litre, a 40 mile spin should cost about £15 - not much you can do to put a smile on your face for an hour at that price

 

You can put a dehumidifier in it for about £40 from Amazon ....

 

I have long been a member of the "drive it regularly to keep it healthy" club. My wife no longer drives her beloved 2006 XK8 Victory Edition convertible, so I take it out at least twice a week for runs of 20 to 30 miles at a stretch. The car responds accordingly and rewards me by throwing very few issues at me as a result. Works for me....

 

If it's a AGM battery, and it was new, and allowed to completely discharge, it's not as simple as hooking up a battery charger to charge these battery's. Google,,, charging of AGM battery - if it is in fact an AGM battery. THEY.CAN.BE.SAVED... There is a little trick.
The "MEGA fuses are in the area of the spare wheel. You'll need to remove the wheel to see their cases. Bolted to the back wall (below seat back) of the spare area....

In the mean time, try ANY kind of battery if just to see that you can get any kind of response from the car - it's bells and whistles.

 

Please clarify what you mean by negative cable under the hood and be VERY careful to not confuse what you think is a negative cable,,, with a positive cable... Getting clear on this IDEA is pretty important right now. Jus say'n