The parent unit has a battery inside . It works on battery or power charger . There is no battery built in the camera . So the camera always need to be plugged in the power outlet when it is working . Features 1,Hassle-Free Portable Monitoring 2,Two way(talk back) 3,Temperature monitoring 4,Built-in lullabies in the camera 5,Automatic night vision 6,Secure, interference free, long range digital signal 7,High contrast 3.2 color LCD monitor 8,Long battery life (18 hours in Vox mode) 9,Multiple languages support(English/French/Spanish/Portuguese/Italian/German/Russian) 10,Built-in lullabies may help the parent comfort the baby fall into asleep. 11,Know your baby's room temperature all the day long without worries! 12,Two way audio between the camera and monitor, you can talk back to baby. 13,Keep an eye on baby all night long with automatic night vision 14,No need to charge the battery for the monitor In the whole night in Vox mode Specification GENERAL: 1,Transmission Frequency: ISM 2400~2483.5 MHz 2,Transmission Power: 17dBm 3,Unobstructed Effective Range: 160ft/50m indoor/850ft/260m outdoor, line of sight 4,Spread Spectrum: AFH & TDMA 5,Modulation Mode: GFSK 6,Operating Temperature: 14 ~ 122 Fahrenheit/- 10 ~ +50 Celsius 7,Operating Humidity: