I have a 13" Late 2013 rMBP which had a cracked display due to accidental damage, I took it in for repair and was informed that the battery was also swollen and needed to be replaced. Apple was kind enough to provide that replacement with no further charge. I haven't had any issues since then, I'm just trying to understand if it's a more widespread issue and to reduce its chances of happening again (if it was somehow caused by me). I'm not completely sure how many cycles the old battery had but if I remember correctly, its total health was above 95%. I did use it plugged in at all times a lot, could that be one of the causes?