well i went to the mall today and i was coming back and my remote didn't work to unlock the doors...i was like damn...i'm gonna set the alarm off by using my key....and of course it did...i need a battery where can i get them and what do i specifically need. it's the factory remote with lock, unlock, panic and trunk version remote..could i get the battery from walmart? and another thing why does it go off and when i use the key?