Battery for surveillance
When the car is turned off, the system is powered by an internal battery that is in the box of the sensor. In surveillance mode, this battery has a duration of up to 72 hours, depending on its charge state and the number of alarms triggered.
When the sensor detects something, you will hear a beep. If you hear the beep again and again when the car ignition is off and you get inside the car, this means that the battery is very low. You will need a minimum of 2.5 hours to fully recharge it.
When you drive, the battery is recharging. However, if the car is parked for a long period of time, the battery will be depleted and you will need to turn on the car ignition in order to recharge it.