Charger question

I noticed that my charger sounds like it has a fan running is that Normal ? Also would a bad charger get to like say 30% charged and shut off or anything like that ? I can charge car and run it for a few trips then it come up with the code -15 . Is my charger giving a false reading and shutting off prematurely?
Thanks Carl

Some chargers had fans. What charger is it?

Yes, chargers can fail in strange ways that will leave your batteries under loved.