SLVT251 July   2026

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 High-Voltage Stackable Architecture
      2. 2.2.2 Electrochemical Impedance Spectroscopy (EIS) Subsystem
      3. 2.2.3 EIS Synchronization Requirement
      4. 2.2.4 PWM Input as Crystal of the First BQ79826Z-Q1
      5. 2.2.5 Temperature Sensing and Multiplexer Network
      6. 2.2.6 Cell Balancing Circuit and Operation
      7. 2.2.7 MCU and System Control Architecture
      8. 2.2.8 Protection and On-Board Diagnostics
    3. 2.3 Highlighted Products
      1. 2.3.1 BQ79826Z-Q1
      2. 2.3.2 TMUX1308
      3. 2.3.3 TMP61
      4. 2.3.4 SN74LXC1T14
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software
    3. 3.3 Test Setup
    4. 3.4 Pack Test Results
      1. 3.4.1 Cell Voltage Reliability Test
      2. 3.4.2 EIS Measurement Repeatability
      3. 3.4.3 Pack EIS Measurement Nyquist Plot
      4. 3.4.4 Current Consumption per BQ79826Z-Q1
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 PCB Layout Recommendations
    2. 4.2 Tools and Software
      1. 4.2.1 Tools
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5.     Trademarks
  11. 5About the Author

3.4.2 EIS Measurement Repeatability

Test step

  1. Put battery pack in the temp chamber and set temperature to room temperature. Wait for thermal equilibrium.
  2. Collect Vcell data from all the cells.
  3. Set excitation current to Imax and measure Z data (0.04Hz to 563Hz) 5 times.
  4. Collect Vcell data from all the cells.

Test result

Magnitude deviation <2%, phase deviation <1°.

Table 3-11 shows the phase and magnitude deviation test result. Repeated scanning curves have high consistency; impedance characteristics under different SOC and temperature are clearly distinguishable.

Table 3-11 Phase and Magnitude Deviation Test Results
Cell No. cell0 cell1 cell2 cell3 cell4 cell5 cell6 cell7 cell8 cell9 cell10 cell11 cell12 cell13 cell14 cell15 cell16 cell17 cell18 cell19 cell20 cell21 cell22 cell23 cell24 cell25
Phase Deviation (degrees) 0.82 0.41 0.64 0.43 0.43 0.42 0.44 0.44 0.39 0.42 0.42 0.43 0.43 0.43 0.47 0.42 0.42 0.42 0.47 0.43 0.45 0.43 0.45 0.47 0.41 0.50
Magnitude Deviation (%) 1.69% 0.77% 0.97% 0.87% 0.72% 0.71% 0.69% 0.75% 0.67% 0.68% 0.69% 0.73% 0.71% 0.70% 0.72% 0.66% 0.68% 0.64% 0.71% 0.76% 0.83% 0.83% 0.83% 0.81% 0.79% 0.77%
Cell No. cell26 cell27 cell28 cell29 cell30 cell31 cell32 cell33 cell34 cell35 cell36 cell37 cell38 cell39 cell40 cell41 cell42 cell43 cell44 cell45 cell46 cell47 cell48 cell49 cell50 cell51
Phase Deviation (degrees) 0.67 0.83 0.69 0.91 0.33 0.54 0.27 0.49 0.32 0.48 0.29 0.42 0.35 0.37 0.38 0.40 0.38 0.36 0.46 0.45 0.40 0.38 0.43 0.39 0.41 0.41
Magnitude Deviation (%) 1.32% 0.74% 0.80% 1.78% 0.45% 0.47% 0.46% 0.53% 0.46% 0.56% 0.53% 0.48% 0.47% 0.53% 0.43% 0.49% 0.51% 0.42% 0.58% 0.54% 0.53% 0.51% 0.56% 0.51% 0.52% 0.54%