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BQ27531EVM: How to change configurations to meet the custom application requirements

Eric Kwok
Prodigy 115 points
Part Number: BQ27531EVM
Other Parts Discussed in Thread: BQ27531-G1, BQ24192

Tool/software:

We are using bq27531evm in our application with a single-cell battery, here is the specifications of the battery:

1.Battery Specification

1.1 Product Specification

Description

Specification

Typical Capacity

3500mAh

Minimum Capacity

3400mAh

Shipment voltage

3.8~3.95 V

Nominal Voltage

3.7V

Fully charge voltage(FC)

4.2V

Fully discharge voltage(FD)

3.0V

Charge Voltage

4.2±0.03V

Standard Charge Method

0.2C CC (constant current) charge to FC Voltage, then CV (constant voltage) charge till charge current decline to 0.01C

Standard Discharge Method

Using 0.2C constant current discharge to FD Voltage

Max. Charge Current

0.2C

0~15℃

0.5C

15~45℃

Max. Discharge Current

0.2C

0~70℃

0.5C

15~60℃

Inner Impedance

pack≤120mΩ

cell≤50mΩ

NTC

10K±1% 3435K

1.2  PCM Electrical Characteristics

Item

Limit Values

Min

Typical

Max

Overcharge Protection voltage

4.23V

4.28V

4.33V

Over-discharge detection voltage

2.7V

2.8V

2.9V

Discharge over-current detection current

3A

/

7A

Overcharge detection delay time

0.8S

1.0S

1.4S

Over-discharge detection delay time

10mS

/

120mS

Short detection delay time

50uS

/

400uS

Current consumption

/

/

8.0uA

2.Custom Application Requirements

We want to set some custom values in our application:

  1. set Fully charge voltage to 4.1V；
  2. set Fully discharge voltage to 3.5V；
  3. set Max. Charge Current to 1A, 0~60℃;  stop charging when temperature rises above 60℃；
  4. no limit to Max. Discharge Current；

3.Our Data Memory configuration file

After calibration, Chem ID program and cycle learning, here is our configuration file of data memory, please help us check if this configuration file is suitable.

bq27531_custom.gg.csv

4.Our Data Memory configuration file

Can you give us a configuration file example that mees the custom application requirements.

  • 0
    TI__Intellectual 2020 points

    Hello Eric,

    Taper Current is too high (1000mA). We usually recommend C/20. So in this case, 3500/20 = 175mA.

    The termination voltage according to the datasheet is 3.0V. This means the gauge detects 0% DoD when the battery voltage is at 3.0V. If you are setting the termination voltage to 3.5V, you must change the reserve capacity of the battery.

    Impedance Track Gauge Configuration For Dynamic Loads (EPOS)

    This document explains the steps to compensate for a different termination voltage.

    It also looks like IT isn't enabled. (See Row 85)

    4. This depends a lot on the individual pack. Unless we have access to the packs, we won't be able to export a custom gg file. However, you can make those changes and send the gg files over to us.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Prodigy 115 points

    Hi, Siddharth, I modify the data memory based on your suggestionss, this gg.csv file, please check.

     bq27531_custom_20240807.gg.csv

  • 0 in reply to Eric Kwok
    TI__Intellectual 2020 points

    Hello Eric,

    This gg looks good.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    TI__Expert 8215 points

    Hi Siddharth,

    Eric may not have fully expressed their real concern, so would like to translate more details and see if you can have any further suggestions.

    ---------------

    We are using power gauge chip bq27531-g1 with charging chip bq24192, circuit design reference to bq27531EVM, schematic <BQ24192+BQ27531.pdf> will be shared through mail as this is public forum, the set of circuit will be responsible for Charge management and charge calculation of the battery.
    Our product type is tablet, battery type is Polymer Li-ion Battery, and input power type is adapter. Based on our practical application needs (posted above), we refer to SLVA725A "Simple Guide to Chemical ID Selection Tool (GPC)" and SLUA903 "Achieving the Successful Learning Cycle" document for chemical ID matching and Golden Learning.

    During the production test, we turned on the tablet, played the video and maximized the volume, and then switched the input power on and off repeatedly (switch on the adapter for 50 seconds, Turn off adapter for 5 seconds) test, and found that when the adapter is turned off, the device(the system load) has a chance of power-down directly. When we do same test but shut off the volume of the video playing, the device will not power off.


    We tried to import the data memory of bq27531-g1 with the defaults values(Import Defaults) and write, also turn on the maximum volume for video playing, and repeat the power input on/off switching (turn on the adapter for 50 seconds, turn off the adapter for 5 seconds), No device power down found.

    Our devices consume approximately 6500mW of power when the maximum volume is turned on. When the volume is turned off, the power consumption is approximately 6000mW; log data for battery discharge in both cases are attached as  <bq27531-g1_max-volume_log.csv> and <bq27531-g1_no-volume_log.csv>.

    We want to know if our modification to Data Memory has caused the device to be possibly powered down. With your previous advice, we have also made several changes to Data memory and still cannot resolve the issue.
    Please help us analyze our actual application needs, parameter profiles and test scenarios.

    0116.bq27531_custom.gg.csv

    bq27531-g1_max-volume_log.csv

    bq27531-g1_no-volume_log.csv

    Thank you!

    Zach

  • 0 in reply to Zach Xia
    TI__Guru 61266 points

    The gauge doesn't directly control if a device powers down. What are the conditions for your device powering down?

    Please attach a register log file that shows time (seconds), voltage, current, temperature, soc, true RM, true FCC.

  • 0 in reply to Dominik Hartl11
    Prodigy 115 points

    Here is the log of a powered down device.

    Tablet_Log_20240904.zip

  • 0 in reply to Eric Kwok
    TI__Expert 8215 points

    Hi Dominik,

    Some values are showing abnormal.

    log_formatted.xlsx

    And here, looks like the algorithm.is giving wrong instructions on the ProgChargingCurrent()  ProgChargingVoltage()

  • 0 in reply to Zach Xia
    TI__Guru 61266 points

    This is by design. The gauge will report 0mV and 0mAh if charging is not allowed, which is the case for a fully charged battery (SOC = 100% in your log file).