When fully charged, the sensor has been able to run continuously for up to six hours. However, the device draws power even when turned off and drains the battery.
When the battery is drained, it can take up to 10 minutes after it is connected to establish communication with the PC. At this time the real-time clock will have to be reset as well. Data from the previous workout session is still available and can be downloaded.
It is recommended to keep the sensor charged and ready to use. The green LED by the USB connector is a battery charge indicator according to the following:
LED on: Charging
LED flashing: Charge error
LED off: Battery fully charged