BQ25890: the accurate battery level cannot be read during charging.

Part Number: BQ25890

Tool/software:

Based on the previous issue, we are currently facing the problem of not being able to read the accurate battery level value while charging. The BATV data obtained from register REG0E is inaccurate and the value is higher than when the charger is not connected. However, the register reading is accurate when discharging, so the accurate battery level cannot be read during charging. How should we handle this? Looking forward to your reply!

  • Hi,

    Could you please give more details when you think register REG0E is inaccurate?

    1. The charger operating conditions such as VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT, VSYS, ISYS.
    2. All the register readings including ADC.

    Thanks,

    Ning.

  • 1.The charger operating conditions such as VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT, VSYS, ISYS.

    The working conditions of the charger include the following values that I can measure:
    VBUS (VBUS pin voltage): 4.75V
    VBAT (BAT pin voltage): 4.279V
    VSYS: 4.278V
    Do you know how to obtain the other IVBUS/IBAT/ISYS?

    2.All the register readings including ADC.

    Register Not Charged Charged
    REG00 0x3F 0x3F
    REG01 0x06 0x06
    REG02 0x5d 0x5d
    REG03 0x36 0x36
    REG04 0x4e 0x4e
    REG05 0x00 0x00
    REG06 0x6e 0x6e
    REG07 0x8d 0x8d
    REG08 0x03 0x03
    REG09 0x44 0x44
    REG0A 0x77 0x77
    REG0B 0x02 0xb6
    REG0C 0x00 0x00
    REG0D 0x12 0x12
    REG0E 0x4d 0x62
    REG0F 0x4d 0x63
    REG10 0x53 0x53
    REG11 0x00 0x96
    REG12 0x00 0x05
    REG13 0x3f 0x3f
    REG14 0x1d 0x1d

  • Hi,

    When not charging, REG0B reads 02 which indicates no input VBUS. Did you measure BAT pin and SYS pin under this condition?

    Thanks,

    Ning.

  • When not charging, REG0B reads 02 which indicates no input VBUS. Did you measure BAT pin and SYS pin under this condition?

    Thanks,

    BAT : 3.960V    SYS: 3.942V

  • Hi,

    REG0E=0x4d is 3.844V. which is close to 3.96V measurement.

    Thanks,

    Ning

  • The difference is not significant, the battery voltage range is only 3.6-4.2v, and the total difference is only 0.7. 3.96v and3.844v the difference is already quite far, and the battery voltage I measured this time is not at the same batter level as last time. What's the point of comparison? Our problem now is not that the battery power measurement is inaccurate when discharging, but that when inserting the charger, the battery power cannot be accurately read. Your suggestion is not related to our question at all. Can you take a look at the question I mentioned earlier and answer it directly, so that we can provide data that is also related to the problem, rather than saying a bunch of irrelevant things? it's over. I still hope you can take this issue seriously, thank you!

  • Hi,

    The chargers are essentially power supplies with complex state machines and analog feedback loops while the gauges are micro-controllers using ADCs and digital logic. The battery monitoring of the BQ25890 is offered as an extra feature in addition to regular charger and is for reference only. The gauge makes more accurate voltage, current and temperature measurements with corresponding accuracy specs compared to the charger. For accurate ADC measurements, a gauge is recommended.

    Thanks,

    Ning.