Left 1999 XK8 in garage over winter months. Battery discharged. Recharged and reconnected. Have started car 10-12 journeys, and each ignition sounded like the battery was getting weaker and weaker. Battery is 2 years old and high quality. Battery incapable of holding charge now? Alternator not charging battery? Some horrible Jag electrics problem common after disconnecting battery? Very grateful for help, as I want to be able to trust it again!

Stick your key in the ignition and turn to start. That should stop the alarm. However, it sounds like your battery still isn't fully charged. Computer things go haywire when battery voltage is 9.6 volts or less.

Do a scan of the car computer, go to a garage and have it connected to a code reader, that will tell you what the problem is.

Sounds like it might have poped the main battery fuse, its in the main fuse box under the hood. some are slip in others are bolt in, Probably at least an 80 amp fuse, when u had it charged what the battery in the car or out,

your battery is low try jump start it good battery

Hi,
A small battery charger may take 24 hours to charge your battery. If you are sure the battery is fully charged then you may want to clean your battery connections.

I ended up taking the car to a dealer for repair.

sounds like a bad battery connection... ck cables at battery...

sound like your brake switch or the fuse.
you have to step on the brake to take it out of park and if it doesnt see that the brake is being pressed it wont unlock the shifter
later paul

You should reboot the system, sometimes these cars hicup so to speak.
Disconnect the battery, both sides, then with it still disconnected turn the key to crank 3-4 times (with the battery disconnected, this just discharges all the ecu's and clears any held memorys)
Reconnect the battery (pos + first)
After that you need to relearn the windows, with the key on or the car running send the windows all the way up, then one at a time, hold the button to bring 1 down and continue to hold for 5 seconds once it is all the way down, do the same for the up position, repeat on the other side and you should be good to go.
JPTCAT

Try and reboot the system.
Disconnect both sides of the battery then crank the car 3-4 times (i know is sounds silly but this fully discharges all the ecu's)
Then reconnect the pos, then neg, reboot the windows and try that.
The xk8 have a lot of quirky problems like this.
JPTCAT