XK8's Eat Batteries,

[GrandTourer]

Of the hundreds of people I know have XK8/R I have not heard anything like that re batteries. Who are these 'experts'?
I have changed my battery last year when my car was 8 years old and not because the battery caused a problem, but because I thought it prudent and felt I got good value over 8 years and 90k miles.

I paid for a new MOURO battery less than £70 at the time, a silver battery which carries a 3 year warranty.

[rogerpalin]

I was a bit surprised by this eats batteries thing as well. Modern ECUs go to a lot of trouble to protect the battery in prolonged shutdown, and certainly my 96 XK8 is frequently left for two to three weeks and always starts first time.

I finally replaced the original Jag battery last year, when it was over 12 years old. Still starting no problem but windows were forever losing their memory. Picked up a genuine Lucas on ebay for £60.

[Billroot]

My XK8 is coming up for 10 years and 80k and still on the original battery. I frequently leave it for weeks without a restart problem. I did leave it for a couple of months once and had to charge the battery before it would start but thought that fair enough.

I wonder why people's experience of this issue is so varied. I see no reason why the car's electronics should need more than a few milliamps when not running but have never bothered to measure it - has anyone else? The only other possibility is internal discharge in the battery itself - never zero but again only a mA or so in a decent battery.

[mike020150]

There does seem to be a wide variance of experiences being expressed in this discussion. Jaguar recommends checking the quiescent current one hour after locking and leaving the car. From that comment, never having measured the current without first locking the car, I wonder if certain circuits remain live for significantly longer periods when the car is unlocked. If so, it's possible that some cars parked for long periods unlocked may suffer different battery failure patterns. Alternatively, the answer may be a lot simpler in that some battery brands may last longer than others! Bear in mind that there's no guarantee that a Jaguar branded battery will always come from the same manufacturer. Mike.

[Billroot]

Now I come to think about it, measuring the current being drawn after switch off may not be straight forward - perhaps Mike knows how to do it. If you leave the boot open, you have to wait long enough for the light to go out. Then if you disconnect the battery to fit an ammeter, the act of reconnecting it will cause some of the electronics to reboot - which will draw current. Lastly, having the alarm set will draw current as the active microwave sensors in the car are working then - or are they on all the time and only monitored when set? Starts to sound like quantum mechanics - the act of measuring something will always change the measurement!

[joejag308]

In the X308 models we have had the same battery problems of losing charge if left for a few days or a few weeks...........
my car had only 22,000 miles on the clock when a bought it and it had a new Jaguar battery at 13,000 miles according to the service history.
I had it until 25,000 and had to renew that Jaguar battery.........so i had everything checked when a bought a new heavy duty Lucas Diesel battery and it was all ok.........but someone gave me the best advice i have had ....buy a
Ctek XS3600 charger and battery conditioner.........when the car is in the garage (it doesnt matter how long) just connect the charger and it turns itself off when the battery is charged up, it automatically turns itself on again when a charge is needed........the unit is a small compact unit small enough go into its own carrying bag.....there are several connecting leads either the crocodile clip type or the eyelet type which you fasten to the terminals permanently, making connection quite an easy thing to do just plug it in to the mains and leave it.....job done..........it did charge a fully drained battery of my neighbors up in 24 hours..........

[deltasierra]

Batteries are simple beasts, either they store electricity or they dont and they are far better better quality in general than they used to be. We use batteries on many vehicles some used daily, some laid up for months. Occasionaly a cell will breakdown early in life, but in general 7 years life would be normal and 12 years in exceptional cases.
One sure way to kill a battery is to leave it connected in a locked vehicle let it discharge and leave it for a month or two discharged. Buying the cheapest battery increases the risk of a fault but paying £ 150 will not eliminate the risk and in the case of a XK8 £ 90 should get a battery that will give long service if used regularly or maintained properly.
If only Jag electrics were as simple, a fault may discharge the battery but if charged quickly will not damage it. A faulty alternator over charging it will not be good but the volt meter on the dash will go off the scale and be obvious. If a new battery goes flat after a month there is a fault with the car

[deltasierra]

Batteries are simple beasts, either they store electricity or they dont and they are far better better quality in general than they used to be. We use batteries on many vehicles some used daily, some laid up for months. Occasionaly a cell will breakdown early in life, but in general 7 years life would be normal and 12 years in exceptional cases.
One sure way to kill a battery is to leave it connected in a locked vehicle let it discharge and leave it for a month or two discharged. Buying the cheapest battery increases the risk of a fault but paying £ 150 will not eliminate the risk and in the case of a XK8 £ 90 should get a battery that will give long service if used regularly or maintained properly.
If only Jag electrics were as simple, a fault may discharge the battery but if charged quickly will not damage it. A faulty alternator over charging it will not be good but the volt meter on the dash will go off the scale and be obvious. If a new battery goes flat after a month there is a fault with the car