A hearing aid comprising: an audio-processing device configured to receive a signal from a microphone and send the signal to a receiver; a hearing aid housing coupled to the audio-processing device, the hearing aid housing comprising: a body comprising an upper shell and a lower shell; a battery door coupled to the body to form a battery cavity, the battery door being movable about an axis of rotation that extends through a circular cross section of the battery cavity to move the battery door between open and closed positions, and further the axis of rotation of the battery door is at least substantially parallel with a cylindrical axis of the battery cavity, and substantially coaxial with a cylindrical axis of a battery positioned in the battery cavity, characterized in that a seal is fit around an interface between the battery door and said lower shell of the hearing aid, and wherein the battery door is configured to at least partially retract into the body of the hearing aid housing, and the battery door is semi-cylindrically shaped such that said battery door is configured substantially as a half cylinder, defined by having an angle θ of an opening of the battery door, said angle being less than or equal to 180 degrees. an audio-processing device configured to receive a signal from a microphone and send the signal to a receiver; a hearing aid housing coupled to the audio-processing device, the hearing aid housing comprising: a body comprising an upper shell and a lower shell; a battery door coupled to the body to form a battery cavity, the battery door being movable about an axis of rotation that extends through a circular cross section of the battery cavity to move the battery door between open and closed positions, and further the axis of rotation of the battery door is at least substantially parallel with a cylindrical axis of the battery cavity, and substantially coaxial with a cylindrical axis of a battery positioned in the battery cavity, characterized in that a seal is fit around an interface between the battery door and said lower shell of the hearing aid, and wherein the battery door is configured to at least partially retract into the body of the hearing aid housing, and the battery door is semi-cylindrically shaped such that said battery door is configured substantially as a half cylinder, defined by having an angle θ of an opening of the battery door, said angle being less than or equal to 180 degrees. a body comprising an upper shell and a lower shell; a battery door coupled to the body to form a battery cavity, the battery door being movable about an axis of rotation that extends through a circular cross section of the battery cavity to move the battery door between open and closed positions, and further the axis of rotation of the battery door is at least substantially parallel with a cylindrical axis of the battery cavity, and substantially coaxial with a cylindrical axis of a battery positioned in the battery cavity, characterized in that a seal is fit around an interface between the battery door and said lower shell of the hearing aid, and wherein the battery door is configured to at least partially retract into the body of the hearing aid housing, and the battery door is semi-cylindrically shaped such that said battery door is configured substantially as a half cylinder, defined by having an angle θ of an opening of the battery door, said angle being less than or equal to 180 degrees.