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BQ27426: General question on Battery self discharge applied on Impedence track devices

Stefano Sivera
Prodigy 201 points
Part Number: BQ27426

Tool/software:

Hi guys,

in my application I would use a fuel gauge with Impedance Track algo (BQ27426 or symilar).

My qpplication require a long time of stand by time ( 2-3 month) and a short time of battery load and in this situation the battery self discharge became more important on SOC of the battery pack.

keep track the algo  of this self discharge ? How can keep track ?

Can I also externalkly modify the self discharge value ?

Thank you 

Best rehards

Stefano 

  • 0
    TI__Mastermind 19761 points

    Hello Stefano, 

    Please see the following from the BQ27426 Datasheet for the iq of the fuel gauge. 

    Regards, 

    Robert. 

  • 0 in reply to Jonny
    Prodigy 201 points

    Hello Robert,

    I'm not clear in my explanation, I will try again

    The LI-ION battery are affected to self discharge current; this is an internal current that discharge the batteries.

    This internal current cannot be measured by gasgauge component because is obviously is "internal".

    In typical application the 90% of the discharge of the battery is due to load currentand is measured bu gasgauge and is computed in the battery SOC and this self discharge do not introduce a relevant error because is negligible.

    In my application I have 3 month of stand by and the self discharge of the battery bacame predominat over load curren and must be computed by the impedance track algo  otherwise the error became too high.

    How the algo keeps track of this self discharge current ?

    I hope to be clear in my explanation, if not please ask me.

    Thank you 

    Best Rgards

    Stefano 

  • 0 in reply to Stefano Sivera
    TI__Mastermind 19761 points

    Hello Stefano, 

    Thank you for clarifying your question, when the gauge is in Normal mode and Sleep mode, the gauge should still track passed charge. 

    Regards, 

    Robert. 

  • 0 in reply to Jonny
    Prodigy 201 points

    Hello Robert, can you explain how ? I have not find any information. Furthermore each battery have different self discharge and I have not find a register where load this parameter.

    BR

    Stefano

  • 0 in reply to Stefano Sivera
    TI__Mastermind 19761 points

    Hello Stefano, 

    I recommend referring to the device TRM to see when the gauge takes measurements. 

    Regards, 

    Robert. 

  • 0 in reply to Jonny
    Prodigy 201 points

    Dear Robert, 

    I've read the TRM of BQ27426 but I not find the answer at my question. Have you the answer to my questions ? If you don't have the answer to my question, it could be a good opportunity to improve your knowledge.

    Thank you 

    BR

    Stefano

  • 0 in reply to Stefano Sivera
    TI__Mastermind 19761 points

    Hey Stefano, 

    My apologies here. The gauge will not track self discharge in relax mode. The gauge will need to obtain a new OCV measurement to correct the SOC reported. 

    Regards, 

    Robert.