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BQ27742-G1: BQ27742-G1 Fuel Gauge Issue

Mitul Tank7
Prodigy 120 points
Part Number: BQ27742-G1

Hello Team,

We are monitoring battery health by BQ27742-G1 Fuel Gauge. (Battery specification - 3.7VDC, 4600mAH, Li-Ion battery)

and we are writing listed below parameter in BQ27742-G1 Fuel Gauge through I2C.

// SUBCLASS ,OFFSET ,DATA
{48, 12, 4600 }, /* Design Capacity = 4600mA
{48, 00, 17020}, /* Design Energy = 3.7 * 4600
{80, 64, 3700}, /* Terminate Voltage 3.7V
{80, 03, 4200}, /* (taper volt) Taper rate 4.2V

But the problem is that battery reach to below terminate voltage (3.7v) still fuel gauge is not disconnect the battery, and battery is on and discharge continuously.

Que 1. - Listed above parameter setting is enough for terminate the voltage?
Que 2. - Which parameter we have to set for terminate the battery?
Que 3. - Can you suggest any other way for battery terminate.

Attached is the schematic of Fuel Gauge

Thanks & Regards,
Mitul Tank

  • 0
    TI__Guru 61006 points

    Terminate Voltage is the voltage that the gauge sets SOC = 0%. The gauge will not turn off the protection FETs at Terminate Voltage.

    See TRM 2.2.1.2:

    Undervoltage protection opens the DSG FET and sets the SafetyStatus()[UVP] flag when measured Voltage() ≤ UV Prot Threshold for UV Prot Delay

    www.ti.com/.../sluuax0c.pdf

  • 0 in reply to Dominik Hartl11
    Prodigy 120 points
    Thank you Dominik for quick reply..
  • 0 in reply to Dominik Hartl11
    Prodigy 160 points
    Hello Dominik,

    Thanks for your reply.

    I am Posting in this thread Behalf Of Mitul Tank.

    I Have Little bit confusion About To terminate Voltage so , i'm facing issue in Bq27742-g1 Battery Fuel Gauge.

    I have set this Parameter for Terminate Voltage:

    Subclass : 80
    Offset : 64
    Data : 3700 / /Terminate Voltage 3.7V as my battery configuration

    i'm also setting this parameters successfully.

    Design Capacity = 4600mA.
    Design Energy = 3.7 * 4600= 17020.
    (taper volt) Taper rate 4.2V.

    When I'm Reading Standard Commands like

    Volt : 3656

    State Of Charge : 0

    Remaining Capacity : 0

    But Fuel Gauge Continuously giving output from the battery.

    Please Provide Me some Suggestion To Protect my Battery in under voltage .




    Best Regards

    Kalarav Parmar
  • 0 in reply to Kalarav Parmar60
    TI__Guru 61006 points
    Terminate Voltage is the voltage where your application shuts off. A typical value would be 3000mV.
    You set it to 3700mV, which is usually the nominal voltage of a LiIon cell (Design Voltage). If you set the terminate voltage to the design voltage then the gauge capacity simulation will terminate at 3700mV and you'll get extremely low capacity and SOC (e.g. 0%).

    What you want to modify is the UV Prot Threshold. This is the threshold that the gauge uses to disconnect the FETs from the battery. See 2.2.1.2, www.ti.com/.../sluuax0c.pdf
  • 0 in reply to Dominik Hartl11
    Prodigy 160 points

    Hello Dominik,

    Thanks For your greater support.

    As Per your suggestion I have seen  column UV Prot Threshold   But there is  Min : 2300, Max: 3100 ,  Def : 2800 mV.

    But i'm confused that  my battery characteristics it required 3700 mv to minimum capacity and my aim to disconnect the FETs from the battery at 3700 mv.

    so, what i can do for this process using Bq27742 Fuel gauge.


    Best Regards
    Kalarav

  • 0 in reply to Kalarav Parmar60
    TI__Guru 61006 points
    Kalarav,

    Please double check if disconnecting the FETs at 3700mV is indeed the requirement. If so then the bq27742 is not compatible with your application. This is not a typical under voltage cut-off value for batteries that the bq27742 supports.

    Regards,
    Dominik.