The charger is microprocessor based, so you need to initialize the charger by turning the charger's ON-OFF switch to the OFF position before connecting it to the battery. When you turn the switch ON, the microprocessor will be able to measure the battery voltage and be properly initialized for the charging cycle.

You can also check the actual battery voltage using the built-in diagnostic program. This will allow you to see if the battery is fully charged and ensure that the bar graph is properly displaying the graphic representation of a full charge.

With the battery fully charged, you can press and hold the MODE button for 20 seconds to force the bar graph to full charge display.

Here's a link to using the diagnostic test:

http://ilbcnu.org/file_share/bionx_instructions.html

Hope that helps.