Lithium battery charger circuit diagram analysis

This battery charger circuit is used to charge rechargeable lithium batteries.

AA batteries are charged with a constant current of 60mA to a cut-off voltage of 2.4V per cell, at which point charging must be terminated.

The charging system shown is designed for multi-cell battery packs of 2 to 6 cells arranged in series or series/parallel. It is crucial that all cells assembled in a battery pack are at the same state of charge (voltage) before charging. The maximum cut-off voltage limit is 15.6V (6×2.6V). Maxim's ICL7665 is a voltage monitor with dual overvoltage/undervoltage detection.

The ICL7665 warns the microprocessor (uP) of overvoltage and undervoltage conditions. It consumes only 3uA of typical operating current. The trip points and hysteresis of both voltage detectors are individually set to any voltage greater than 1.3V via external resistors. The ICL7665 operates from any supply voltage ranging from 1.6V to 16V while monitoring voltages from 1.3V to hundreds of volts.