If you purchased one of the Pikachu charging banks from The Pokemon Company, you might be dealing with an issue with your bank, particularly the fact that while using it the batteries may be becoming hot and generating smoke.
The Pokemon Company has issued a statement on the banks, including both the ones with Pikachu on them and the regular Poke Ball patterns, advising users to stop using the devices and return them to Pokemon Center and Pokemon Stores or by using a special form to return them.
That’s a surefire sign you don’t want to use it anymore, no matter how cute the bank is!