Unless it has a Lithium Ion battery it will gradually self discharge.
Batteries can not hold a charge forever. This is why packs of batteries sold in stores are dated. They discharge on there own.
Batteries slowly discharge over time even if not connected to anything.
car batteries do discharge over time. That's why trickle chargers are good if a vehicle is being stored.
If the Power Bank was on 100% and you didnt use it to charge anything, will the battery slowly run out? Or will it stay 100% until you use it?
