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BQ27426: Questions about BQ27426 configuration

Nicky Lim
Genius 3195 points
Part Number: BQ27426

Hello, 

Using bq27426 and current setting is as below.

Temp Source[01]: External Thermistor 설정.

Subclass ID: 82, Offset: 6 (Design Capacity) 2300mAh

Subclass ID: 82, Offset: 8 (Design Energy) 8800mWh

 

What I want to know is

1.  what means of this equation for Subclass ID: 82, Offset: 0(Qmax Cell 0). Please let me clarify it.

      Qmax (mAh) = Qmax Cell 0 × Design Capacity/2^14

2. Set Design Capacity to  2300mAh, but FullChargeCapacity(0x0e,0x0f) value is 2200.

      Why its value is 2200 not 2300?

3. Is there any other registers which has to be set?

 

Could you let me get your answer about above questions?

Regards,

Nicky

  • 0
    TI__Guru 61006 points

    1. Qmax is the chemical capacity of the cell. It is calculated by the gauge and stored in a data memory parameter (Qmax Cell x). The format is unit less and the number needs to be multiplied by the Design Capacity and divided by 2^14.

    2, The Full Charge Capacity is calculated by the gauge and depends on several factors (for example load current and temperature). The Design Capacity is a nominal capacity given by the manufacturer of the cell. The gauge determines the Full Charge Capacity by simulating a discharge with a specific load(see load mode and load select in the TRM) - A high load will cause the Full Charge Capacity to drop. As will a low temperature.

    3. See the following app note. It's for the bq27421 but it also applies to the bq27426