When your Parent Unit is removed from the AC Adaptor and in Sound Activated Mode (VOX ON), the rechargeable batteries will last approximately 10 hrs:
- When the Parent Unit has the sound constantly ON and/or also using continuous sound transmission VOX OFF (search articles for VOX info) as with all cordless devices this will naturally drain the rechargeable batteries when it is not connected to the power
- In addition to this, the amount of noise in each home is different, therefore as the Parent Unit is constantly transmitting background noises, music etc. these will also drain the battery power in this unit
This is indicative of any portable device (such as your mobile phone) that constantly streams information, video etc. These functions use more power than when any unit is standby/power save mode.