Hi all, not a electronic guru, but understand most of what I can do and what I can't. I have a question for those that know.
Don't drive the XK8 near as much as I should, so I have a battery 1.5A charger I plug in every few days. Most of the time I do it in the truck hooked up directly to the battery, but on three occasions I hooked it up to the + next to the ABS Module and a shock tower bolt. Unplugged after a few hours.
Never had a problem with it in the trunk. On three times I went to open the door, just to see how bright the interior lights were (keep the top down and car covered most of the time), so can't check the window up or down, the battery was dead. It's almost like the charger was drawing current, is there a reverse diode in the line going back to the battery???
Any way lesson learned.


Wayne

 

Wayne,


No diodes in the way. For the purpose of battery charging (not jumping) the engine-compartment terminals you described should be just fine.


Could the battery itself be done for?

 

Dennis, Don't think so on the battery. It stays up for a couple weeks in the summer with no charging, maybe longer, just never had the reason to leave it longer. I have checked all the normal drain areas described on the Forum and yes I did a couple that were in effect.


Wayne

 

Check the power amp as it will drain a steady 2 amps when one of the output chips fail like mine did. If the power amp is warm even long after the car has been shut off thats the sign of a shorted output chip. Will kill the battery in about 2 days.


Dave

 

Wayne,


I don't have an idea yet about what is going on, but if you have a digital voltmeter, one worthwhile test ...


Hook up the charger to the engine-compartment terminals, and then measure the voltage there and also at the battery. These should agree to within, at most, .01 or .02 volts.

 

Another thing to try is to use a digital meter on its highest amp scale and put it in series with the minus of the battery. At first you will see some current draw but after about 15-20 minutes it should settle down to less than about 80ma draw. If it stays more than that and never drops then something is drawing current or a module is not shutting down.



Dave

 

Dave, Power amp?? Like I said, are we talking radio, CD???


Wayne


Dennis, will do on your test, thanks.

 

Yes the one right under the pump and over the cd player. The Toshiba output IC's are supposed to shut off when the radio is off but if one has a problem it will draw 2 amps 24/7.


Dave

 

Dave, Thanks, will do and If I find one is warn, since the radio has not been on for 2 weeks I'll let you know and ask where you got yours to solve the problem. Still going to check on the voltage up front and rear. Something is not right, but if I'm only putting in 1.5A and that power amp is drawing 2A, kind of a losing battle.


Wayne

 

The amp is 8 channel and has 4 two channel Toshiba output chips. One of mine failed and caused a similar problem to what you are seeing. I initially found it by using an amp meter in series with the battery. When I pulled the fuse for the amp the draw went away. Then i took the pc board out of the amp so the chips were exposed and then plugged just the power connector to it. The bad chip got hot in just seconds. The new chips are $9.95 including shipping from HERE.

Way cheaper than replacing the whole amp.


Dave

 

Dave, I did go back and find your thread on your issue and it explained what I will be looking for, if that's it, I will just pull the fuse for now and get the parts ordered.


Thanks again,


Wayne

 

This perhaps may not apply to the Jag, but 3 years ago I had a similar problem with my F-350. A diode had failed in the alternator, causing a constant drain. A 7.3 PSD ('99 120K) needs all the juice it can get from both batteries. Changed out the alternator .. problem solved.

 

Thanks all, I need to find this, as winter looks like it will be long. From what I have read our Jaguars become the night of the living dead when their life's blood is taken away and your try and wake them up.


Wayne

 

Dave's idea sounds to me like a very good fit to the symptoms. Here's hoping ...

Wayne, IMO it's perfectly OK to leave the car without power for an extended period, so long as we don't get locked out of something. The battery of course is another story; we don't want to let that discharge. Some guys remove the battery from the car for the winter.

 

All, I don't think the main problem is solved but here are a few items that will rattle the gray matter. Using a thermo temperature reader after charging the battery to 12.89V, I scanned every wire in the trunk area, ran the light through the holes in the amp with no higher reading than anywhere else. All were about 50F, so if there was any heating in that part, surely as cold as everything was, it would have showed up.
Dennis I was going to take a reading on the battery and then the one under the bonnet. When I was getting my reading in the trunk it had already dropped to 12.54V, ODD! We are talking a minute after disconnecting the charger. I watched it for a few more minutes and right at 20 seconds it would drop a hundredth of a volt.
WTF. Disconnected the leads and stayed with it, same song second verse, so I'm watching a lose of .01V every 20 seconds or so. Gentlemen, we have a winner, or a loser in this case. Back to Advance, of course they have to charge it over night and check it in the morning, can't blame them for that, but feel sure a replacement is in the works.
Will let you, but also will keep check on things.


Wayne

 

Wayne,


I've got a bad feeling about that battery. The 12.89 Volts is sort of what the charger would like to see happen, a little higher than even a perfect battery will hold actually. 12.54-and-falling is what your particular battery can hold.


The measurement that will tell us most is where the battery voltage settles after, say, 4+ hours ... being neither charged nor discharged during that interval. South of abut 12.4, she's toast. South of, say, 12.45, on life support


edit: I forgot how cold it is already. Numbers to look for may be a little lower than given above. Let's see where it settles out.

 

You may have seen the 'surface charge' dissipating. Common for all freshly charged batteries. Before testing, after charging, turn on your low beam headlights for about twenty seconds then make measurements.

Also consider that a 1.5amp charger isn't much to push through to the battery in the trunk. Yes, I understand voltage drop, etc. but you stated you never had a problem when charging directly at the battery. I'm not certain what Jaguar's draw spec is but someone mentioned 80ma, which is fairly high compared to most vehicles. Typically 26-30ma is normal spec for most cars. Just remember that whatever the spec is you have to feed that draw first then 'warm up' the wiring all the way back to the battery. When you connect to the battery maybe you were actually connected directly to the battery's terminals rather than to the clamps? That could also cause a drop when connecting elsewhere.

 

We can bleed some surface charge to get an immediate reading (it's possible to do too much or too little), but the most accurate reading comes from letting the battery rest after charging. 4+ hours is good; 8 hours is plenty.

Unless there's a wiring problem, the engine-compartment terminals, battery clamps, or the battery terminals themselves are all equivalent for charging. A digital voltmeter can be used to check this. Really. There probably won't be more than 1 or 2 one-hundredth of a volt difference, if it's even measurable.

If there is a source of significant resistance in the circuit when using a charger, it's in a place we never think about; those skinny wires with their weak clamps coming out of the charger itself.

 

IMHO any vehicle with one or more computers should be kept powered at all times as unfortunately with age the ECU caps dry out and there is a risk that they will not boot up again.

 

ALL, great to get advise and different directions to go. Thanks to all.
I had the battery charged at Advance and they say the battery is fine. 12.58V after charge and two days later 12.50V, so they may be right.
One thing I see is the Beav opinion of the cables could be the resistance that is causing the small charger not to be effective and possibly a draw. I need to confirm this.
Been really busy over the last few days, so I just wanted to up date all and will get in garage shortly.


Wayne