The charging base completes a self-check every time the hearing aids are placed into the charging base. This self-check ensures that the hearing aids are properly inserted, and that they can be charged (for example, that silver-zinc rechargeable batteries have not been swapped out with non-rechargeable zinc-air batteries). During the self-check, the charging base lights flashes green 5 times. If issues are identified during the self-check, the charging base will display a solid red light.