BQ40Z50-R1: charging is not stable after 5 cycle life

Hi Steel,

Based on the log file, it seems like the charge FET is continuously getting disabled and recovering by the status of the XCHG bit. This bit typically becomes set and disables the charge FET if a protection is triggered. Can you please share the .gg file of the gauge so we can look at the protection thresholds?

Regards,

Anthony

Hi Anthony,

   see below for the .gg file.

    5050.4S2P.gg.csv

Hi Steel,

Thanks for sending these files, we will look into the log file with this in mind now. Regarding the log file, there are several points where the individual cell voltages drop to zero. Are the cells being physically removed at any point or are the secured to the board?

Regards,

Anthony

Hi Anthony,

    They are are the secured to the board, not removed.

Hi Steel,

Thank you for confirming, In the log file, the toggling of the FET is apparent, however there is no reflection of a protection being triggered in the SafetyStatus() or PFStatus(). If this is observed on bqStudio in real time, is there any movement in these registers when the FETs become disabled and re-enabled?

Also, please confirm the connection between EV2400 and the device. The log file seems to contain error statements that could be coming from the connection.

Regards,

Anthony 

Hi Anthony,

    the connection between EV2400 and the device is good, some times  i saw some changes like cell voltage is 0V and temperature is abnoraml in registers and ack error in Studio.

    when i keep the charge on and off for some time, and once the battery voltage become higher , there is no ack error and charging is stable, no FET toggling.

Hi Anthony,

    Any comments on how this happened?

Hi Steel,

When this issue does occur, it seems like the cell voltages are not near the shutdown voltage, which could cause a different read if reached. Just to confirm, is there any sort of wire extension being used on the EV2400 or is there a singular wire attached?

Regards,

Anthony

Hi Anthony,

    We use some wire extension from battery board to connect EV2400, even not being charged, we still can see such registers change from BQ studio. I recorded a one-minute video so that you can see it clearly, and there is no safety issue happens during the registers change.

Hi Steel,

If a wire extender is being used, is there a USB isolator in use as well? Does this problem occur if there is only the main wire attached from host to the board?

Regards,

Anthony

Hi Anthony,

    the wire extender refers to the wires solder to PCB and a connector to connect with EV 2400, no USB isolator is used.

    this issue will happen even no connection with EV2400.

Hi Anthony,

   I would like to call this issue  mofet ON/OFF/ON issue.

  Just to clarity that this issue will not only occur during the beginning of charging, bu also occur during standby after full discharge, some phenomenons are bleow:

      1.measure the voltage  on VCC/VC1/VC2/VC3/VC4 pins and the voltage is stable, no big varation.

       2.the  CHG pin is about 2.5 sconds on and 0.5 second off with cycles.

       3. some registers sometimes will have abormal values, such as cell voltage is 0V, temperature is -273.2C.

        4. the battery voltage is around 12.0V.

   Some further tests are performed on this:

     1. once we use a power supply to charge the battery voltage to a litter higer to about 13,2V, then this ON/OFF/ON phenomenon will stop and charging process is back to normal.

      2. during this ON/OFF/ON stage, when I send a RESET command through BQ studio, the issue still exist.

      3. during this ON/OFF/ON stage, when I  re-program the V1.06 firmwre through BQ studio, the issue still exist.

       4. we learned from the BQ40Z50-R1 to BQ40Z50-R2 change list that R1 can update to R2, so we update the firmware from V1.06 to V2.08, and then the ON/OFF/ON issue stop and also rrgisters values are normal.

        Can you kindly provide a detailed explanation to me why V2.08 can slove this prolem?

Hi Steel,

At this time, is the standard 100kHz SMBus communication being used or is 400kHz? Since there were a significant amount of changes done between the R1 and R2 firmware, there is a possibility that this type of issue was alleviated by one of the changes made. We can go back through the change log to try and find an explanation.

Regards,

Anthony

Hi Anthony,

    The configuration is the same, both are with100kHz SMBus communication.

Hi Anthony,

    I found that in this situation, once I unseal the R1 IC, the R1 IC will become sealed again in one or two seconds, does this mean the IC is reset continuously?

Hi Steel,

Yes, if the gauge is becoming sealed again after unsealing it, then there is a reset occurring. What is the voltage being seen from the cells at this time? Could the gauge be possibly falling into shutdown and exiting?

Regards,

Anthony

Hi Anthony,

   after unsealing, the voltage of the cells in the BQ studio sometimes show 0V, sometimes normal.

   How to confirm the gauge falling into shutdown and exiting? what's the possible reasons to cause the gauge have such performance?

Hi Steel,

The most common type of shutdown in this type of situation is a Voltage Based Shutdown, which the process can be seen below. Upon exiting to normal mode, a reset will be conducted:

Has there been any change between how the shutdown parameters are set on the R1 and R2 setups?

Regards,

Anthony

Hi Anthony,

    the shutdown parameters are same on R1 and R2 setups.

    Today I compared the settings on our R1 samples and defalut settings on fresh R1 in our stock, I found that once i changed the term voltage from 10400 to default 9000, the ON/OFF/ON issue stops, when i send RESET command, still ok.

      Then once i set the value to 10400 again and send RESET command, the issue appear again.

       I have some questions below:

        a.How does the term voltage cause the R1 to appear the ON/OFF/ON  reset issue?

         b. the term voltage threshold is compared with which voltage in the R1 register?  BAT pin voltage?

         c.Does R2 make any improvements on term voltage judgement? why does same settings, R1 has issue while R2 hasn't.

Hi Steel,

If the term voltage is causing a change in the behavior, than I believe there is something causing the voltage to be unstable enough to have it pass the threshold. The Term Voltage is based on the sum of the cell readings, so if one cell were to be disconnected or not read than this could potentially push it below the original value but not the other.

Regards,

Anthony

Hi Anthony,

    My thinking is that this should not caused by cell voltage unstable，the reasons are below:

     first , we use oscilloscope measured the VC1/VC2/VC3/V4 pins, they are stable.

     second, same sample, just change the version from R1 V1.06 to R2 V2.08 with gauge same configuration, same term voltage, then the issue disappear.

      Kindly please reply my previous question a and c, for b, i undertand that it compared with the sum of the cell readings.

       a.How does the term voltage cause the R1 to appear the ON/OFF/ON  reset issue?

       c.Does R2 make any improvements on term voltage judgement? why does same settings, R1 has issue while R2 hasn't.

Hi Steel,

I believe that if this issue is alleviated by the Term Voltage being changed to a lower value, then there is something that is causing the voltage reading to pass the threshold. In normal operation, the term voltage should not affect the performance of the gauge unless when the threshold is passed. I do not see anything in the change log that is a direct change to how the gauge processes the term voltage, however one of the changes could of included a change of how the gauge processes the voltage read. The full change log between the two can be found below:

https://www.ti.com/lit/pdf/slua833 

Regards,

Anthony