You’re always allowed to board the plane with your hearing aid batteries in the device. For regulations on bringing spare hearing aid batteries, please consider contacting your airline.
It’s possible, yes. But we can never guarantee perfect functionality - so we recommend charging your Panasonic batteries with a Panasonic or eneloop charger.
This is a vibration noise which occurs when electric current flows through a transformer or a winding wire inside a component part. However, the charger may still be used without any concern as there is no need to worry from a safety point of view.
There are some best cases to keep stored batteries in best shape: store them in their original packaging, never mix up different batteries and store them at room temperature or in a cool environment.
As zinc air hearing aid batteries operate differently than other batteries they have different characteristics. In winter, rooms may be drier, warmer or badly ventilated. These effects can disturb the performance of your batteries.