If you like I can try to get you in contact with the person making them.I do not however have the source code.
voltage divider is not a good solution for me,
My preferred solution was to have a voltage controlled oscillator on each cell and capacitavly couple the signals into an arduino where it measured the frequency.
the ground of the battery is the same as the ground of arduino.
I would really like some more info, and the help needed to really understand this