1 Introduction

The temperature that the battery operates in plays a major role in battery performance, charging, discharging and longevity. Prolonged exposure to high temperatures can accelerate aging and can result in thermal runaway and explosion. Conversely, low temperatures increase the battery resistance causing the charge capacity to drop significantly. The Li-ion battery is generally recommended to operate in the 0-45°C charge temperature range and -20-6°C discharge temperature range.

To address this, the BMS is used to monitor the temperature data from battery and then transfer the data to host microcontroller for regulating battery temperature. The silicon-based linear thermistor, TMP61, which has a tolerance of ±1% between 0°C to 70°C and a wide operating range of -65°C to 150°C, is recommended for temperature measurement. 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 measuring TMP61 voltage.

The BQ76972 device can support up to nine external thermistors measurements. But, in high cell count applications, the system requires more channels to measure every single cell temperature. A multiplexer circuit can be used together with BQ76972 to support more thermistor measurements.

This document shows the design considerations of expanding temperature measurement channels and improving measurement accuracy.