I've had the same device for quite some years now, and played a lot with it changing ROMs a few times. Recently I've been experiencing sudden drops in battery charge, here's a screenshot:
What could be the reason for this? Is the battery old and faulty and in need of a replacement? Or is the current ROM (Chromium ROM Build 11) faulty?
I am prepared to see a degradation in battery life after so many years, but I would expect the drop to be linear. Instead it is lasting quite long while in stand-by, and drops quickly when I use it, but no app appears to be draining it.
EDIT: I've tried resetting battery stats, it's of no use.