Charge the instrument for at least 12 hrs. After having full charged it, unplug the charger and wait 10 minutes (around). Switch ON the instrument and enter in the HARDWARE INFO Menu. Read the battery voltage and take note of it: should be from 4.15 V to 4.20 V. Leave the instrument switched on for 2 hrs about (better if in simulation mode) and read again the battery Voltage: take note (should from 3.80 to 3.90 V). If values are less, contact sales@compass-italy.com and send the us the data of Voltage you registerd.