I know Rexton claims the charger also dries the hearing aids but do not believe it. The fact that you never open the battery doors with the rechargeable batteries makes it so any moisture that gets in the case stays in the case. The last 3 generations of Rexton hearing aids have all had issues with moisture in the battery compartment (KS3, KS4, Quintra) and the charger did not change with the Trax.