You could have a short or drain on your system... this cause the battery to went dead after you park....

few thing to look at.. first it could be your glove box light, trunk light, and many other light.. you need to know what cause the drain...

by using an Amp metter. not volts .. you disconnect your ground battery cable.
now hock one proble of the amp metter to the ground cable and the other proble to the battery (ground post).. Note making sure that your voltmeter is set on Amp or you will burn out the meter if its on volt (I burn out 2 metter) fuse.

Now if you saw with the key off what is your Amp drawing ?? if .01 than it is normal if it show .04 or more than it is too much ..

Now with the Amp meter connect where it at.. slowly one by one remove one fues at the time.. (now see if the Amp metter drop back to .01 amp ) as you remove 1 by one you will see that one of the fuse will show the drop in Amp.. this is the cause to your problem (that fuse that show the drop in amp is where you need to look for the short)

or you could have a burn out rectifer inside your altornator ?? is allow the current to drain back this will cause the battery to go weak and dead...


all this problem happend to my BMW 2 week ago in the end it was the fuse number 21 that cause the drain in the system...

hope you fine this input helpfull.. my english is poor but if you read it slowly and carefuly you will understand what I am saying

please let us know what you fine.

first you need a new battery forsure the old is dead it can not hold the charge any longer ... take is you Krangen or some place the will check it for free with the load on...