A hearing device , comprising: a housing being configured to be positioned behind the pinna of a wearer, the housing holding electronic components including an input transducer, an audio processor for processing audio signals from the input transducer, an output transducer for outputting the processed audio signals, a battery device connected to power the electronic components, and the battery device stored in a battery drawer , where when in a closed state the battery drawer is flush with a part of the housing, so as to form a smooth surface of the hearing device , and the battery drawer is configured to pivot at a battery pivot point when moving from the closed state to an open state, the battery drawer further having a lock mechanism ensuring that the battery drawer is maintained in the closed state until operated to an unlocked state, and the housing includes an opening configured to receive a key device to operate the lock mechanism from the locked state to the unlocked state thereby allowing the battery drawer to change from the closed state to the open state, wherein the lock mechanism includes a body being forced against an inner part of the housing by a spring element in a closed state of the hearing aid and wherein during opening the key device pushes the body in a direction so as to compress the spring element along a spring axis thereof, wherein the opening in the housing includes an indicator device for visually indicating to the wearer if the hearing device is intended for wearing on/at the left or right ear. wherein the indicator device having an opening configured for receiving the key device . a housing being configured to be positioned behind the pinna of a wearer, the housing holding electronic components including an input transducer, an audio processor for processing audio signals from the input transducer, an output transducer for outputting the processed audio signals, a battery device connected to power the electronic components, and the battery device stored in a battery drawer , where when in a closed state the battery drawer is flush with a part of the housing, so as to form a smooth surface of the hearing device , and the battery drawer is configured to pivot at a battery pivot point when moving from the closed state to an open state, the battery drawer further having a lock mechanism ensuring that the battery drawer is maintained in the closed state until operated to an unlocked state, and the housing includes an opening configured to receive a key device to operate the lock mechanism from the locked state to the unlocked state thereby allowing the battery drawer to change from the closed state to the open state, wherein the lock mechanism includes a body being forced against an inner part of the housing by a spring element in a closed state of the hearing aid and wherein during opening the key device pushes the body in a direction so as to compress the spring element along a spring axis thereof, wherein the opening in the housing includes an indicator device for visually indicating to the wearer if the hearing device is intended for wearing on/at the left or right ear. wherein the indicator device having an opening configured for receiving the key device . <EOS>