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BQ40Z80: Cells are not balancing

Goran Temunovic
Prodigy 30 points
Part Number: BQ40Z80
Other Parts Discussed in Thread: GPCCHEM

Hello everyone,

We have a BMS board with BQ40Z80 battery manager and we're using 6-s 20Ah LiPo battery. We have managed to go through learning process and get golden file so far. Now we are testing the rest of the functionalities using BQ studio. Currently we have a problem with balancing which seems that is not starting at all.

We have implemented external balancing circuit as on the figure below, but the only difference is that we do not have circuit for balancing the 7th cell. 

Using BQ studio in Settings->Configuration->Balancing configuration cell balancing is enabled CB = 1, cell balancing at rest is enabled CBR = 1, cell balancing at sleep is enabled CBS = 1, and both internal and external balancing was tested CBM = 0/1. 

During charging, status bits are set in a way that charging is detected, however no balancing was detected. For this purpose 1st and 2nd cell, before connecting battery to BMS board, were internationally charged more in order to have higher voltages and to have detect balancing process more easily. Also, current meter was attached to 1st and 2nd cell too, but no current during this process is detected. Battery was charged with 2A.

In the figures below, screenshot of BQ studio was take to present the situation more easily:

The BQ chip behaves as expected, but we're obviously missing something regarding balancing. Please provide us any information you have. 

Best regard,

Goran.

 

  • 0
    TI__Guru** 105760 points

    Hello Goran,

    Were you able to get an update status of 0x0E? Can you share your GPCCHEM report and the learning cycle you performed with the final .gg file?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 30 points

    Hello Wyatt,

    Thanks for quick reply.

    At the end of learning cycle the update status was 0x0E. After that, the golden file, that we got on your BQ40Z80EVM development board, was uploaded on our custom board based on BQ40Z80. After importing it we disabled GaugeEN and and enabled LifetimeEN bit, and now the update status is not 0x0E anymore.

    Is this good approach? In your application document it is not clear which steps should be taken after learning process in order to get golden file and also after importing golden files into BQ chip. Please provide us steps that we should go through in order to get golden file properly and also what setting have do be done after importing golden file.

    You will find necessary files attached. Thanks in advance.

    Best regards,

    Goran.

    Data Memory.gg.csv

    1881.GPCPackaged-report.zip

  • 0 in reply to Goran Temunovic
    TI__Guru** 105760 points

    Hello Goran,

    The Gauge Enable should be sent before the gauge is used, we used to recommend that for older gauges but it's okay to always leave IT enabled.

    The gauge will not cell balance without Impedance Track enabled.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 30 points

    Hello Wyatt,

    Enabling gauge and impedance track resolved our problem! Now cell balance is working! CB status bit is now set to 1 and amper meter detects current!

    Thanks a lot. Have a nice day.

    Best,

    Goran.