SLUAAF8 October   2021 BQ24707 , BQ24707A , BQ24725A , BQ24735 , BQ24770 , BQ24780S , BQ24800 , BQ25700A , BQ25708 , BQ25710 , BQ25720 , BQ25730 , BQ28Z610-R1 , BQ4050 , BQ40Z50 , BQ40Z50-R1 , BQ40Z50-R2 , BQ40Z80

 

  1.   Trademarks
  2. 1Introduction
  3. 2Smart Battery Setup
    1. 2.1 Gauge Setup
      1. 2.1.1 I2C System Differences
    2. 2.2 Charger Setup
  4. 3Communication Protocol
  5. 4Data Collected
  6. 5Summary
  7.   A Appendix
    1.     A.1 General Setup
    2.     A.2 Gauge Setup - SMBus
    3.     A.3 Gauge Setup - I2C
    4.     A.4 Charger Setup
    5.     A.5 Charge Voltage Example
    6.     A.6 Charge Current Example
  8.   B References

4 Data Collected

All data collected was using the BQ40Z50 device with R4 firmware and the BQ25710 device which follow the SBS guidelines. Both of the data sets collected used the system outlined in the block diagram, with the EV2400 tied on the SMBus as well.

Relax Discharge Relax (RDR) cycle to find the chemistry ID using the Gauge Parameter Calculator Tool.

GUID-68E7128A-0BA4-42FB-AF9E-3C12524FF13E-low.png Figure 4-1 RDR Cycle for the GPCCHEM Tool

During the next charge cycle after a relax period, the Update Status (LStatus in the bqStudio log) changed from 0x04 to 0x05, indicating that two valid Open Circuit Voltage (OCV) readings were taken and the gauge updated Qmax. On the next discharge, the gauge will update the resistance table (Ra table) to complete the learning process(6).

GUID-AC243234-D721-433E-BA02-6C22E4F55436-low.png Figure 4-2 Full Charge Cycle Using SMBus SBS

The voltage thresholds are seen during charging between precharge voltage, low voltage, medium voltage, high voltage as the current changes in each voltage region.

In the precharge region when the voltage is slowly rising in Figure 4-2, the set charge current is 100 mA, but 10 mA is being supplied. That is because the FET Options[PCHG_COMM] = 0 by default, which enables the precharge FET and not the charge FET. For the charge current to directly reflect the broadcasted value, FET Options[PCHG_COMM] must be set to 1. With the precharge FET enabled, the current is limited by the series resistor.