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BQ25601: Uncontinuous Charging

Fan Wu
Intellectual 705 points
Part Number: BQ25601
Other Parts Discussed in Thread: BQSTUDIO

Hi TI,

We are using BQ25601 in our system. However, we found after it enter into constant voltage status and charging current drop to nearly 1A,.Then, for some reason, the charging current will jump to a high value (2A ) for a while then drop back.to lower value, like 1A. The charging current will oscillating until battery is full. Can I ask why and is it expected behavior? Thanks!

cheers

FanCopy of Lark_charging_23C_04run.xlsx 

  • 0
    TI__Genius 11850 points

    Hi Fan,

    This behavior is not expected. The charge current should taper down smoothly in CV mode. For example, in the waveform below, I set ICHG = 1.5 A and ITERM = 0.3 A. The charge current tapered down smoothly until the device entered termination.

    Can you please describe your test setup and test conditions in more detail so I can try to reproduce this issue? For example:

    1) Are you using an EVM or your own circuit?

    2) What is your adapter's voltage and current capability?

    3) What kind of battery are you using?

    4) Is there any system load connected?

    5) Is anything unusual being reported in the status and fault registers? Please provide a BQStudio screenshot to show your register settings.

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Intellectual 705 points

    Hi Angelo,

    Thanks for your feedback! Please check my replies as below.

    1) My own circuit

    2) Adapter is 5V/2A output

    3) We are using Lithium-ion battery pack which contains two parallel 18650 cells inside.

    4) system loading is around 200-300mA

    5) I have not captured the value of REG09 when the phenomenon happened. I am going to retest and get the value out when abnormal phenomenon happening.  Below is the value I dumped when it is working normally.

    REG00-0X13

    REG01-0X1A

    REG02-0XA0

    REG03-0X22

    REG04-0X60

    REG05-0X9F

    REG06-0X66

    REG07-0X4C

    REG08-0X74

    REG09-0X00 I saw 0x80 once

    REG0A-0XA0

    REG0B-0X11

    Thanks!

    cheers

    Fan

  • 0 in reply to Fan Wu
    TI__Genius 11850 points

    Hi Fan,

    Thanks for providing that information.

    Just to rule a few possibilities out, please make the following changes and try again:

    1) Disable the watchdog timer.

    2) Disconnect the system load. This should leave only the adapter, the charger, and your battery pack.

    3) Decrease the charge current from 1.92 A to 1.5 A.

    After making the changes above, do you still see ICHG oscillation in CV mode? If so, at what VBAT does this window of oscillation start and stop? In other words, what is the battery voltage at the two points indicated below?

    Also, I agree that it would be helpful if you could provide a register dump during the ICHG oscillation region.

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    TI__Genius 11850 points

    Hi Fan,

    We haven't heard back from you. We are assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Intellectual 705 points

    Hi Angelo,

    Thanks for your remind. We just finished the temperature protection test to make sure this issue does not make effect on safety. Also we found this issue is not consistent. So we need to spend more time in duplication. I will update to you once we have any progress. 

    cheers

    Fan