Battery Monitor and Balancer with Integrated EIS BQ79826Z-Q1

The BQ79826Z-Q1 is a stackable battery monitor and balancer for high-voltage battery packs. It performs the core cell supervising function — measuring every cell voltage and the associated temperatures, and balancing cells against each other — and adds an integrated EIS engine that measures cell impedance in place.

Conventional monitoring reports voltage, current and temperature, which describes how much charge a cell holds. Impedance describes the condition of the cell: internal resistance, ageing behaviour, and the electrochemical processes behind them. Making that measurement inside the pack, on the device already responsible for cell supervision, means condition data can be gathered during operation instead of in a laboratory.

• Cell coverage: up to 26 cells per device, configurable for smaller module sizes
• Measurement accuracy: ±1.7 mV cell voltage accuracy across the operating temperature range
• EIS engine: integrated impedance measurement with 1% accuracy under the conditions stated by the manufacturer, supporting both global and local excitation
• Balancing: passive cell balancing with integrated FETs, up to 300 mA
• Stacking: daisy-chain communication across up to 128 devices, addressing pack architectures to 1500 V
• Qualification: AEC-Q100 automotive qualified, developed for ASIL D functional safety
• Operating range: −40 °C to 125 °C, 100-pin HTQFP package

The device is supported by an evaluation module (BQ79826Q1EVM-086) and a reference design (TIDA-010978), a stackable battery monitoring unit with integrated EIS that documents verified performance test data at pack scale. It is intended for engineers designing the electronics of a battery system — cell supervising circuits, battery monitoring units and the surrounding BMS architecture — rather than sold as a finished battery management system.