96-cell scalable Battery Management System for EV and HEV application

Project Overview


A European automotive company.


To design a scalable Battery Management System (BMS) for easy adoption to any battery pack size needed with fast time to market and automotive graded hardware.


Our team developed an evaluation kit based on NXP’s MPC5775B microcontroller and MC33771B analog front end. Our platform significantly cuts the development time for complex onboard vehicle equipment and allows engineers to focus on critical system components.

Our automotive platform employs highly complex system elements:

  • An Enhanced Self-correcting cell model 
  • Current measurement and relay control system
  • CAN communication bus
  • Development tools
  • Examples of GUI applications

Cell modeling and firmware generation

The system is based on software that can be adapted to customer requirements. The current version of the software and cell model implements the following features:

Measurement functions
  • voltage measurement;
  • temperature measurement;
  • current measurement;
  • isolation measurement.
Estimation functions
  • State of Charge (SOC);
  • State of Function (SOF)/power estimation;
  • State of Health (SOH);
  • State of Energy (SOE);
  • charge time estimation.
Control functions
  • state control mode;
  • wake-up/power-up/power-down;
  • cell balancing control;
  • battery thermal management;
  • relay control;
  • plug in charge management;
  • HVIL generation and detection;
  • crash signal detection and handling;
  • history recording.
Communication and diagnostics
  • CAN - and service tool communication;
  • diagnostic procedure support;
  • fault handling;
  • flashing and programming;
  • BMS calibration.
Technical functions (TSC)Safety Measures (SMs)

Business Value

The customer received a software and hardware platform that makes it possible to create a BMS with the following key capabilities:

  • Signal acquisition and processing
  • Cell balancing
  • State of function calculation
  • State of C calculation
  • State of health calculation
  • History recording
  • Charge duration forecast
  • Main contactors control including pre-charge and service life counter
  • Battery thermal management (cooling or heating)
  • Insulation monitoring
  • HV Battery State Machine (connect, disconnect, pre-charge)
  • Diagnostic procedure suppor
  • Fault handling (strategy)
  • CAN communication
  • Reprogramming
  • Safety monitoring

Project summary

Promwad successfully developed a software and hardware platform based on NXP MPC5775B MCU and MC33771B AFE serves to protect and manage battery packs of any size designed according to automotive standards.

How It's Made

Hardware platform components

Master-slave architecture

The device is based on the Master-Slave architecture, which makes it flexible and versatile in its application. Each battery module has its own Slave BMS, which measures individual cell voltages and module temperature, and performs the function of cell voltage balancing.

All Slave Units are interconnected by an information interface leading to the master board with microcontroller. The Master board processes the results of the voltage, current and temperature measurements and performs the simulation of the battery according to the loaded model.

Master board

The master board is based on the NXP MPC5775B microcontroller. The master board is responsible for the main data processing and control functions. The master board implements the following feature and interfaces:

  • Real-time battery simulation.
  • CAN-bus communication.
  • Daisy chain communication with slave cards.
  • Automotive grade EMC protection.
  • Isolated current measurement interface.
  • Isolated relay control interface.

Slave board

The slave board is based on the analog front end NXP MC33771B from NXP. Each battery module has its own Slave board, which is responsible for measuring the voltages and temperatures of the module. Our developed Slave board supports battery modules with configuration of 7-12 cells per module.

Basic technical features

MCUThe MPC5775B AEC100, ASIL-D support, 2 x Power Architecture z7 cores with 264 MHz
Memory256 KB RAM, 4MB ROM
Battery configuration
Cell count in series12 cells per module, up to 56 modules
Battery currentUp to 1200 A
Slave board
Power9.6…61.6 V operation voltage
InterfacesIsolated 2.0 Mbps differential communication or 4.0 Mbps SPI
Master board
Power9V-16V operation voltage
Interface connectorsCAN bus type: ISO 11898, CAN 2.0A


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