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BQ27520EVM: Evaluation Module Stopped responding during middle of charge discharge test for determining the ChemID

Edward Hunckler
Prodigy 220 points
Part Number: BQ27520EVM
Other Parts Discussed in Thread: BQSTUDIO

I have recently been using the bq27520EVM to determine the ChemID of a 3.7v LiPo battery that I am using.

I was running a charge/discharge cycle with a programmable load set to disconnect from the device when the load dropped below 3v.  Soon after the load disconnected itself, the current draw dropped.  It seems the battery itself continued to discharge at a lower rate.  At this time the EVM stopped responding to the bq Studio software.  When I arrived in the morning, the battery was at 0V and drawing no current (this could potentially be the internal protection circuit on the single cell LiPo).  

I disconnected/reconnected everything, restarted my computer, and tried to reconnect to the EVM with the bqStudio software, but I have been unable to re-establish a connection with the device.

I am curious to know if anyone has any thoughts on why the device seems to have bricked itself during this test.  

Has anyone seen this behavior before, or have any theories on why this happened?

The plot shows the voltage (mV) and current (mA) vs elapsed time (s).

The data log from the test is below.

 LP803235_1_10_19.log

Thanks for any feedback,

Eddie

  • 0
    TI__Guru* 76230 points

    Hi Eddie

    It appears your battery protection kicking in and dropping the battery voltage to 0V may have been what made the chip to be bricked. Perhaps the voltage dropped lower than the threshold that the vbat of the device can handle during the the action of the protector? I would recommend replacing the chip and see if you are able to re-establish communication.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 220 points

    So, as it turns out, the EVM battery under test powers the bq27520 chip. When the battery under test voltage dropped below some threshold, the communication stopped because the chip shut off.  Changing the battery to a charged state and starting the system up again causes it to work fine.  Also, the no communication can happen when the battery is disconnected from the module.  These things become obvious now, but it did not occur to me at the time.

    Unfortunately, I only identified this after purchasing another EVM and experienced the same communication issue.

    Best,

    Eddie