On my Nissan (sorry) the alternator failed and killed the battery !!!!! It (the alternator) had been playing up, dim charge light, but other than that all seemed well, then a totally flat battery. I charged it overnight and all seemed fine when I started it the next morning, but at the next start (10 mins later) absolutely nothing !!!!
The local auto electrician took it away and rebuilt the alternator in his workshop, he had the battery on charge and drove it out onto the driveway, closed the doors and then went to start it again, nothing !!!!!!! So a new battery and, touch wood, all fine since (20mths).
In his opinion, running the car with a slightly under-performing alternator damaged the battery terminally.
A lesson for me to remember !!
Andy