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BQ25895M: Question about BQ25895M charging IC

Yu You
Prodigy 40 points
Part Number: BQ25895M

It is clear that the conditions for the end of charging are that the voltage meets the set 4.17v and the charging current is less than 64mA. However, the charging time of the BQ25895M charging IC is close to 12 hours, of which there are 8 hours to maintain 50mA current. After investigation, the charging voltage has been unable to reach 4.17v, and is maintained at about 4.15v. When I unplug the DC and plug in the DC, the voltage will rise and the charging will end. May I ask how this phenomenon is caused?

  • 0
    TI__Mastermind 21575 points

    Hello, 

    Thank you for reaching out via E2E. There are a few possible conditions which could prevent the BQ25895M from terminating charge. Can you please help to share a read of all registers with the ADC enabled while VBAT is 'stuck' at 4.15V and 50mA charging so I can review the status of the BQ25895M to verify there is not a condition that would be preventing termination?

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 40 points

    Hello,

    7F 1F F1 3A 10 10 56 CD D3 40 93 7E 00 23 5D 5E 54 E1 01 10 3A FF

    These registers have values that the voltage has not been able to increase.

    7F 1F 71 3A 10 10 56 CD D3 40 93 76 00 23 5D 5F 54 E1 04 10 3A FF

    The values of these registers are plugged in after the DC is unplugged.

  • 0 in reply to Yu You
    TI__Mastermind 21575 points

    Hello, 

    Thank you for sharing the register outputs in both scenarios. 

    For the case where you report the battery voltage does not increase REG0B = 7E, which indicates charge is terminated. Therefore, it is expected that BQ25895M is no longer charging the battery and voltage is not increasing.  For this case the battery is likely hitting 4.17V threshold, then when charge stops the battery voltage is relaxing a small amount.

    I am not sure what you use in your system to judge when charge is complete, but you should be referring to the CHRG_STAT bits in REG0B. 

    When you unplug and plug back in the DC input a new charge cycle is initiated. This is shown by CHG_STAT now indicating fast charge in the 2nd set of registers. 

    Based on your description of the behavior and the register statues the bQ25895M appears to be operating as expected. 

    Best Regards,

    Garrett