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

A.1 General Setup

The battery used in this example is the LG INR21700 M50T. The battery manufacturer specifications were used for programming the gauge with the recommended charging current, charging voltage, charge termination, and discharge termination.

Some of the battery specifications used for this example, from the manufacturer:

Item

Notes

Specification

Energy

By standandard Charge or Discharge

Nominal 18.2 Wh

Nominal Voltage

Average through standard charge and discharge

3.63 V

Standard Charge

Constant current

Constant voltage

End current (cut off)

0.3C (1,455 mA)

4.2 V

50 mA

Minimum Discharge Voltage

In all operations, the minimum closed voltage circuit value for a cell

2.5 V

Following the specifications for the battery chosen, the following modifications were made to the flash memory of the gauge:

  1. Design Capacity mAh = 4850 mAh
  2. Design Capacity cWh = 3640 cWh
  3. Design Voltage = 8400 mV
  4. Taper Current = 100 mA
  5. Quit Current = 20 mA
  6. DA Configuration register to match number of cells and set NR bit
  7. Any values updated from calibration
  8. The advanced charge algorithm described in this section.

The parameters described in the General Setup section are needed for most gauges to start the learning cycle and are dependent on the battery being used.

The EV2400 can be used as shown in the block diagram to log data during charge and discharge cycles. The EV2400 is essentially the MCU of the system, but just for logging. The EV2400 can be added to the SMBus lines so the charger, gauge, and EV2400 will all be on the same bus. Logging and configuration changes can then be done to both the charger and gauge during testing using bqStudio.

To configure the charger with all three devices on the same bus, bqStudio must be opened with the chargers designated bqz file before connecting the EV2400, otherwise bqStudio will auto-connect to the gauge. The advanced communication tab in the BQ40Z50 GUI can also be used to communicate with the charger.

Multiple primary devices on the same communication bus is not recommended because it can lead to arbitration errors. This is why broadcast mode should only be used when the gauge is the only primary device.