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bq40z60 Charging stops at 3.2V (charging voltage 4.2V)

Other Parts Discussed in Thread: BQ40Z60, BQ40Z60EVM-578, BQSTUDIO

I'm using the bq40z60 on a bq40z60EVM-578 Evaluation Board to charge a 3300mAh Lithium Ion 2s1p battery pack.

It stops charging at 6.4V (3.2V/cell) even though the charging voltage is 8.2V (4.1V/cell). As far as I can tell, no protection flags have been set (see the attached image).  

Please also find attached the .srec file.

Interestingly charging resumes if I move the J4 jumper on the Evaluation Board from the 2S to the 3S position. However, charging occurs at 500mA (as it did when beginning to charge the battery after full discharge with the jumper in the 2S position) instead of the specified charge current of 700mA. 

pimConfig082516.zip

  • Thanks in advance for your reply!
    Alex
  • You Minimum Output Voltage and Voltage Resolution parameters are set higher than we would recommend. Try setting them to 4214mV and 16. Try applying a 10V AC Adapter voltage and also calibrate the ACP voltage. You can calibrating it by disabling the charger, applying the Adapter voltage and using the Applied Pack Voltage section on the Advanced calibration screen in bqStudio.
  • Thank you for your quick reply Thomas!

    Charging now continues until full. However, Current still shows 550mA during charging instead of the specified 700mA Charging Current. Can you think of any solutions? I will mark the post solved, and if you like I can start a new thread regarding this issue.

    Thank you and best regards,

    Alex

    pimConfig082616.zip

  • It is possible that the charging current is less than the ChargingCurrent parameter, depending on how close to the end of charge the cell are. I would insert a current meter in the charging path and check the accuracy of the charging current reporting.
  • The charging current is approximately 500mA instead of the specified 700mA from the time one begins charging after discharging to the low voltage region. See the first attached image. It remains approximately 500mA into the medium voltage region.

    The second attached image shows the charging current measured (Y-Axis) with a multimeter versus specified charge current (X-Axis) as well as the charging current reported in bqStudio versus the specified charge current.

     

    Do you have any idea why the measured current doesn't match the specified current given these measurements?