Building a Superior Battery Monitor with the bq27x00

The bq27x00 is a complete gas gauge solution for lithium-ion and lithium-polymer batteries. The bq27x00 also has internal registers and control commands that enable the host to use it as a battery monitor. A battery gas gauge solution can be built one of two ways: ignore all algorithms built into the bq27x00 and use the primitive functions to build a fully customized solution, or use some of the higher level functions, such as self-discharge capacity loss estimate, taper current full battery detection, and end-of-discharge detection to build a semi-custom solution with less development time. An accurate direct reading of average current that is updated every 5.12 seconds, even at light loads, and a built-in digital magnitude filter (DMF) function, enable the host to build a more complete gas gauge solution with superior performance than is possible using other battery monitors. This superior solution may also be achieved without requiring significant communication or processing bandwidth from the host. The ability to directly read the capacity value using the built-in bq27x00 algorithms can be valuable during initialization of the host after the battery pack has been removed and externally charged or replace with a different pack. The automatic sleep function of the bq27x00 can reduce the power consumption when the system is off, or the battery pack is removed. The host may choose to use either an HDQ (bq27000) or I2C (bq27200) communication protocol.