Batteries are covered under your warranty, but from defects in material or workmanship.
But for example , They are able to tell if you left the lights on for 2 nights while you were away for instance. If so.. you have kille dthe battery and it wont recover.
you would be amazed at how many people leave lights on, or comfort access keys IN the car, and end up with dead batteries.
That is why you hear both sides of the story... and no one really confesses to leaving the lights on.
of course you could have a draw, or a bad alternator...
X1, R58 JCW, M2 in my future if planets align