Here is a typical implementation of pack-based gauging with a bq34z100, and cell protection and balancing done externally using a bq77 series hardware based device. The two devices in this case work essentially independently of each other, although they can monitor the same sense resistor. The only function of the bq34z100 is to provide the gas gauging and communicate pack capacity level to the system. The gauge basically treats the pack as one “giant” single cell. The high voltage from the pack is divided down to a level corresponding to a single cell with the external divider near the top right of the diagram. The resistor values are scaled appropriately for the pack so that a full pack corresponds to 4.2V into the “BAT” pin of the bq34z100. The resistor divider is switched on with the external small signal MOSFETS only to take voltage readings. It is turned off most of the time to avoid continuous drain on the battery pack. The safety / protection and cell balancing functions are provided by the bq77 series device shown on the right side of the drawing.  For further information, the data sheets for all of these devices can be found at www.ti.com/battery.