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Original question:

BQ25616: Can't enter the constant current charging mode

Regarding the accuracy of the BQ4050 fuel gauge: How long does it take for accuracy to decrease in a static state？

Chalice_Liu
Intellectual 300 points
Other Parts Discussed in Thread: GPCCEDV

Hi, TI Experts

    I have a mass-produced project (2S1P withBQ4050).Recently, I received several customer complaints about the battery, and the customer reported that the battery level is not accurate and cannot be fully charged to 100%.

    I confirmed the battery status as soon as I received the battery sample, As shown in the figure below, the battery has triggered overcharge protection, but the RSOC of the battery is only 6%. This is extremely unreasonable.

    

     Our Battery will be shipped in "Shutdown" Mode. Customers will activate the battery before installation. After the battery is activated, due to the self-consumption of the battery itself (about 350uA) and the self-consumption of the client host. In total, it is about 1~2mA. This small current will not be detected and calculated by the fuel gauge, so the accuracy of the power will get worse and worse as time goes by. When the time reaches a certain level, the battery may show the kind of situation that customers feedback.

     Generally, after this happens, the battery will return to normal after standard full charge and full discharge.As shown below:

     What I want to know is how long it takes for the fuel gauge to become inaccurate, and whether there are better preventive measures？I also attached the GG document below, please help analyze it, thanks.

    IS1099G-202044007079.gg.csv

     

  • 0
    TI__Guru** 104825 points

    Hello Chalice,

    What steps did you take before sending out the gauge? If there's a lot of quiescent current losses during shutdown the gauge may need to be cycled after it is received. The Impedance Track algorithm would more accurately account for this because it uses an OCV lookup table when it wakes up from shutdown.

    Sincerely,

    Wyatt Keller 

  • 0 in reply to Wyatt Keller
    Intellectual 300 points

    Hello, Keller

        Before we send out the battery, Conventional battery pack tests will be performed normally, such as voltage, internal resistance, overcurrent, etc. In the end is the "Seal" and "Shutdown". 

        For a single battery pack, once the battery is Shutdown, the self-consumption is only about (PCM<2uA+Cell<15uA). So the above abnormality is more likely to appear after the battery is activated.

        Our customers understand this situation, but what they want to know more is how long it will take for this situation to occur?

  • 0 in reply to Chalice_Liu
    TI__Guru** 104825 points

    Hello Chalice,

    Was the GPCCEDV tool used to find the parameters for the CEDV gauge? Can you share the report?

    I haven't seen this situation before, so I can't tell you exactly how long it will take for this to occur.

    Sincerely,

    Wyatt Keller