The bq2014H NiCd/NiMH Gas Gauge IC is intended for batterypack or in-system installation to maintain an accurate record of available battery capacity. The IC monitors a voltage drop across a sense resistor connected in series between the negative battery terminal and ground to determine charge and discharge activity of the battery. Compensations for battery temperature, self-discharge, and rate of discharge are applied to the charge counter to provide available capacity information across a wide range of operating conditions. Battery capacity is automatically recalibrated, or "learned," in the course of a discharge cycle from full to empty. Nominal available capacity may be directly indicated using a five-segment LED display. The bq2014H also supports a simple single-line bidirectional serial link to an external processor (common ground). The 5kb/s HDQ bus interface reduces communications overhead in the external microcontroller. Internal registers include available capacity and energy, temperature, voltage and current, and battery status. The external processor may also overwrite some of the bq2014H gas gauge data registers. The bq2014H can operate from the batteries in the pack. The REF output and an external transistor allow a simple, inexpensive voltage regulator to supply power to the circuit from the cells.