REPLACING THE SENSOR MODULE BATTERY
Step 1: Remove the sensor module from the headband.
Step 2: Find the small hole on the side of the sensor module which you will use to open the lid of the sensor module enclosure.
Step 3: Use a sim card pin ( you can also use a safety pin, thumbtack, or even a paper clip) and gently insert it 1/8th of an inch into the hole. Once inserted, use the pin to gently pry the lid upward by pushing downward on the pin (be careful as you can break the side of the plastic enclosure).
Step 4: Replace the battery
Step 5: Put the sensor module lid back on and snap it in place using the LED light window to guide you in orientation the lid correctly.