LabQuest Battery Calibration:
This is a quick procedure that will calibrate the LabQuest’s charge indicator to the battery that is currently installed. This process does not test the battery, but it will make the battery gauge more accurate.
1. Turn on the LabQuest.
2. Connect LabQuest to AC power and let it charge overnight (at least 9 hours) with the power on.
3. With the LabQuest still on, disconnect the fully-charged unit from AC power.
      Note: Leaving the LabQuest on during charging is only necessary when recalibrating the battery.

See also:
     How do I test the battery on the original LabQuest?
     Original LabQuest Battery Troubleshooting and FAQs