SLUA857A December 2017 – September 2022 BQ27426
Host-side application of a single-cell gas gauge, bq27426, requires direct battery voltage measurement from the battery pack. For a single-cell pack, the bq27426 uses the BAT pin to measure the pack voltage directly with the BAT pin internal translation circuits enabled. The maximum voltage that can be applied to the BAT pin is 5 V.
If a 2-S battery pack is used, the bq27426 cannot directly measure the battery voltage because the pack voltage may be much higher than the maximum operating voltage on the BAT pin. An external resistive voltage divider circuit is required to divide down the battery voltage to the range equivalent of a single-cell battery.