Battery pack monitoring, balancing, and protection system for Li-Ion and Li-Polymer cells in 3, 4 or 5 series configurations

Boost battery lifetime and safety in industrial and consumer applications with multicell battery monitoring and balancing IC

With a high-precision ADC to provide cell voltage, stack voltage and temperature conversion via external NTC, the L9961 also monitors stack current via a high-accuracy CSA and includes a Coulomb counter supporting pack overcurrent detection.
In addition to cell balancing and SOC/SOH estimation, the L9961 guarantees protection of the battery pack fuse to prevent fire and explosion hazards, protection of the battery pack against over/under voltage conditions and over/under temperature, protection against over current (both directions) and short-circuit in discharge events.


Key features of L9961

  • Very low current consumption in both deep-sleep mode (i.e. 2 μA) and standby mode (i.e. 5 μA)
  • High accuracy in cell voltage measurements (i.e. maximum error of ± 15 mV in the 1.5 to 4.5 V range, for -40 °C < TJ < 105 °C) with over/under voltage detection and balance under voltage protection
  • High accuracy in battery current measurements (i.e. maximum error of 0.25%) with Coulomb Counting, over current detection and short-circuit in discharge protection
  • Stack voltage monitoring with over/under voltage detection and plausibility check
  • Pack temperature monitoring via NTC sensor with over/under temperature detection and pack fuse management
  • I2C peripheral for device programming and data transfers over I2C bus
  • Hot plug robustness
  • Embedded NVM for configuration parameters storage

Application examples

Cordless power tools Cordless power tools
 UPS and backup energy storage systems
 Battery operated medical equipment


Recommended resources


STEVAL-L99615C evaluation board for industrial BMS applications with up to 5 cells
Evaluation kit

Includes STM32G0 Nucleo-64 development board and a dedicated software package with STM32G071RB firmware and a user-friendly GUI to help reduce development time and cost.

User-friendly GUI for L9961 evaluation board

Complete software pack includes sample scripts to enable the monitoring of key parameters such as cell voltage, battery current and temperature acquisitions, and the binary code to flash the STM32G0 Nucleo-64 development board.


Battery Management Systems: 36 V and beyond from BMS ICs to the MCU

Highly scalable battery management systems from low-voltage up to 400/800/1200 V batteries for e-mobility and industrial applications.

ST makes lithium batteries perform better and last longer with high-accuracy BMS controller
Press announcement

Discover the many built-in features and advantages of our L9961 BMS device with market-leading accuracy and flexibility to enhance the performance, lifetime, and safety of Li-ion and Li-polymer batteries...