For stack voltages under 4.5 V max, it is not necessary to provide an external voltage divider network. The internal 5:1 divider should be selected by clearing the VOLTSEL bit in the Pack Configuration register. The default value for Voltage Divider is 5000 (representing the internal 5000:1000 mV divider) when no external divider resistor is used, and the default number of series cells = 1. In the 1-S case, there is usually no requirement to calibrate the voltage measurement, since the internal divider is calibrated during factory test to within 2 mV.