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BQ27421-G1: Battery level reading fluctuates randomly

Anjaly V
Prodigy 40 points
Part Number: BQ27421-G1
Other Parts Discussed in Thread: EV2400, BQSTUDIO, BQ27542EVM, BQ27426, GPCCHEM

Hi,

I am using BQ27421-G1 fuel guage for my project. But I am facing issue with the readings. The following are the parameters I have used.

FG_DESIGN_CAPACITY 0x0578 /**<DESIGN CAPACITY of the Li-ion battery used */

FG_DESIGN_ENERGY 0x143C /**<DESIGN Energy of the Li-ion battery used */

FG_TERMINAL_VOLTAGE 0x0BB8 /**<TERMINAL VOLTAGE of the Li-ion battery used */

FG_TAPER_RATE 0x366 /**<TAPER RATE of the Li-ion battery used */

 Battery SoC read from BQ27421-G1 shows unexpected behavior. it shows 30% as SoC and suddenly the Soc Changes to 0% within 1 minute.  Can anybody advice on this issue?

  • 0
    TI__Guru* 76230 points

    Hi Anjaly

    Do you have bqstudio and and ev2300 or ev2400 to connect your board to so see if you observe the same behaviour? Do you have the batdet flag set to ensure the gauge is detecting a battery? 

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 40 points
    HI,
    I tested with bqstudio and ev2400. The fuel guage I used is BQ27542EVM. The settings I have given in bqstudio is
    Design Capacity 1400
    Design Energy 5180
    But I have not find an option to enter the taper rate? Is there any option to enter the same.
    The findings I have made is : When the bqstudio shows 64% reading, still my custom device shows 0%. What could be the issue?
  • 0 in reply to Anjaly V
    TI__Guru* 76230 points
    HI Anjaly,
    I am confused. Is the issue with the bq27542 or the bq27426? These are two different device types with different parameter nomenclature in some instances. eg the 542 doesn't have taper rate but rather taper current.

    If you are refering to the bq27426, you need to make sure that the default chem id on the device will be a good match for your cells, i.e run our online too gpcchem. If it is a match, then you need to configure the parameters as defined in the evm quick start guide (have you reviewed this document?). Pls cafefully follow the instructions and you will get your system working if the battery is a good match.
    thanks
    Onyx