SLUAA45 April   2020 BQ27Z561

 

  1.   End of Discharge SOC Jump Elimination
    1.     Trademarks
    2. 1 Introduction
    3. 2 Improve Battery Modeling
      1. 2.1 Improve Battery Modeling -- Get Matched ChemID
      2. 2.2 Improve Battery Modeling -- Use GPCRB Tool to Optimize Low-Temperature Performance
    4. 3 Optimize Gauge Configurations
      1. 3.1 Optimize Gauge Configuration -- Load Prediction
        1. 3.1.1 Load Mode
        2. 3.1.2 Load Select
        3. 3.1.3 Discharge Current Threshold and Quit Current
      2. 3.2 Optimize Gauge Configuration -- Enable Smoothing to 0% in Discharge Mode
      3. 3.3 Optimize Gauge Configuration -- Enable Fast Resistance Scaling
      4. 3.4 Optimize Gauge Configuration -- EDV in Steep Zone
    5. 4 Achieve Successful Ra Table, Qmax and DOD0 Learning
      1. 4.1 Complete a Learning Cycle to Update Ra Table and Qmax
      2. 4.2 Add a Dedicated Relaxation to Update DOD0
    6. 5 References

3.1 Optimize Gauge Configuration -- Load Prediction

Load prediction is an essential part of IT algorithm. Gauge cannot know future load would be, so has to make a prediction of future load.

IT gauge determines the remaining capacity (RM) using a voltage-simulation method based on predicted load current (Ipred). Simulation starts from the present DODstart, and the future cell voltage is calculated by increasing DOD repeatedly in small steps as shown in Equation 2.

Equation 2. sluaa45-equaton-2.gif

In Equation 2, OCV is the battery open-circuit voltage derived from OCV[DOD] table, R is the battery resistance calculated by R = Ra × exp(Rb × T). When the simulated voltage Upred reaches the battery termination voltage, the DOD corresponding to this voltage is captured as DODfinal. RM can be calculated as shown in Equation 3.

Equation 3. sluaa45-equaton-3.gif

From the above equations, it can be inferred that Ipred affects the remaining capacity accuracy. Sometimes SOC jump is due to load prediction that is not configured well, Ipred is far from the actual load, which leads to an overestimation of remaining capacity followed by the SOC jump at terminate voltage

The following sections provide a guidance of load prediction settings.