This Lithium battery charger circuit is dedicated to charge lithium batteries. It uses 2 chips, voltage regulator LM317T and ICL7665 warns microprocessors (μPs) of overvoltage and undervoltage conditions.
Charging is completed with a constant current of 60 ma for Aa cells to a cutoff voltage of 2.4 V per cell, at which point the charge should be terminated. The charging system shown is made for multi-cell lithium battery packs of two to six series-connected cells or series/parallel arrangements. It is important that all of the cells built in the pack are at an identical state-of-charge (voltage) before charging. The maximum upper cut-off voltage is 15.6 V (6 x 2.6 V).