After a long night of partying and completely depleting the battery, one who is on charger spends the next 10-20 hours sleeping.
The term was more common in the time before smartphones when mobiles only needed charging once a week. (See also Nokia 3310 )
-Friday's party was awful. It's Saturday morning, and I don't even have a hangover.
-It's Sunday, Panki! You've been on the charger for too long.
(to be on the charger)