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BQ27742-G1: Query related how fuel gauge exactly work in Discharge and charge mode.

Part Number: BQ27742-G1
Other Parts Discussed in Thread: BQSTUDIO

Hello sir,

Urgent !! I have setup for testing fuel gauge basically to educate as my project requirement (for future use) and for battery. I am using BQ27742-G1 , EVM2400 , BQstudio and battery specification is (Tenergy 3.7v 1400mAh Li-ion).

First simply i check voltage, avgcurrent and SOC. SOC did not update as my voltage change in charge and discharge mode. So i go through process of chem id(rel-dis-rel) for new chem id. And after i got new chem id i just upload to fuel gauge and SOC level start to change in charge and discharge mode correctly.

I take one battery having voltage around 3730mV and connect load at load side which draw around (avg voltage : - 250 to - 300mA  by connecting resister). Then fuel gauge suddenly indicates voltage around 2980mV and SOC: 0% because terminate voltage is 3000mV, so this is right operation. But if i disconnect load voltage level increase around 3720mV, But fuel gauge does not wakeup (stable in shutdown mode) and it should resume by itself after detecting higher voltage than terminate voltage but it does not. so please give me suggestion what should i do ?? and if i reattach battery in socket with no load connected it work fine . Indiacte SOC and other parameter as well.

for my application i want device shutdown if voltage is less than 3600mV and maximum charging capacity till battery 4200mV. and it should indicate soc : 0% at 3600mV and soc : 100% at 4200mV, for this where should i need to make change in data memory. ? and do i need to go throgh learning cycle process for this problem or this is actually real characteristic of fuel gauge. 

Thanking you,

Regards

Reena patel 

  • You will have to go through a learning cycle. Can you let us know your end application, why is the terminate voltage 3600 mV?
  • Hello sir,

    Basically in my application, i have stepper motor and this motor works on more than 3600mV. And i know as per voltage, SOC change whether fuel gauge on relax mode, discharge mode and charge mode. Fuel gauge check that voltage and responds based on it. According to different step of stepper motor for different operation, load vary based on it. 

    And i have already changed design capacity and all other necessary parameters. 

    so do i need to set terminate voltage based on load ?

    if i go through learning cycle process. what change i can get in fuel gauge. ? 

    Thanks

    Reena patel

  • No, terminate voltage is based on battery specs. We just keep it high enough so that we don't lose capacity when the battery discharges.

    A learning cycle is mandatory for all impedance track gauges. This helps the gauge learn the actual capacity of the cell (Qmax) and also the resistance along the path of dsg from full charge to terminate voltage (RSOC 100% to 0%).

    A proper selection of load select and load mode will improve performance of the gauge.