Why is my home charger able to charge my battery more after my portable charging case says the battery is charged?

The charging case typically charges a battery to around 95% or more of its total capacity to indicate it is charged.  Since the charging capacity of the battery case, compared to a powered plug, is less, in order not to waste the remaining charge of the cases battery it will stop the charging process and conserve power for the next charge. When the e-cigarette battery starts to  reach its full capacity charge, the efficiency of the case charger lowers and therefore will determine the battery has a full charge and complete the charging process on its own.  Its smart!

Since direct power from the home charger will always be constant, it is a more efficient means of charging and therefore has no concerns about the charge and power remaining on its own.  This will be true across any systems like that use portable chargers.