SLUAAR3 December   2023 BQ27426 , BQ27427 , BQ27Z561 , BQ27Z746 , BQ28Z610 , BQ34Z100 , BQ40Z50 , BQ40Z80

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Voltage Correlation
  6. 3Voltage + IR Correction
  7. 4Coulomb Counting
  8. 5CEDV
  9. 6Impedance Track
  10. 7Algorithm Comparisons
    1. 7.1 Calculating SOC Error
      1. 7.1.1 Calculating True SOC
      2. 7.1.2 Finding Calculated SOC for Voltage Correlation & Voltage + IR Correction
      3. 7.1.3 Finding Calculated SOC for Coulomb Counting
    2. 7.2 Comparing SOC Error
  11. 8Summary
  12. 9References

7.1.1 Calculating True SOC

The first step is to calculate the passed charge (dQ) between two sample points by using Equation 4. The passed charge is a rolling sum of the previous passed charge. Note that dQ is normalized to hours so if the data is reported in seconds, then the elapsed time needs to be converted into hours by dividing by 3600.

Equation 4. d Q N = E l a p s e d T i m e N + 1 - E l a p s e d T i m e N × C u r r e n t 3600 + d Q N - 1

Next is to calculate the battery’s true full charge capacity, which is the sum of all passed charge. After that, the remaining capacity can be calculated for each sample point using Equation 5.

Equation 5. C a l c u l a t e d R e m a i n i n g C a p a c i t y = C a l c u l a t e d F C C - d Q

Finally, the true SOC can be found for each sample point using Equation 6.

Equation 6. T r u e S O C = C a l c u l a t e d R e m a i n i n g C a p a c i t y T r u e F C C × 100