1 Introduction

Battery-powered products are becoming more and more popular, such as energy storage, vacuum cleaners, power tools, e-bikes and e-scooters. Because of the weight limit and longer endurance needs, the battery cell chemistry is shifting from Lead-acid to Li-ion, Li-polymer, or Li-ion phosphate (LiFePO4) types. Good measurement accuracy is always required, especially the cell voltage, pack current, and cell temperature. Precision is necessary for accurate protections and battery pack state of charge (SoC) calculations. This is especially true for LiFePO4 battery pack applications because of the flat voltage.

This article takes a deeper look at current sensing for lithium-based battery, including the error calculation and proper system configurations. The high-accuracy battery monitors and protectors for battery packs, BQ76972, which is designed especially for applications using lithium-ion, lithium-polymer or lithium-phosphate cells, are used for an example.