Solution 1: After the first charge, the operating time is less than the time mentioned in the manual
The rechargeable batteries only reach their full capacity after you have charged and discharged them at least four times.
Solution 2: The volume of the parent unit may be set too high, which causes the parent unit to consume a lot of energy
Lower the volume of the parent unit.
Solution 3: The microphone sensitivity level of the baby unit may be set too high, which causes the parent unit to consume a lot of energy
Decrease the microphone sensitivity level (with the SENSITIVITY button) on the parent unit.