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BQ27426: BQ27426 Soc is NOT correct for new battery

Mike#
Prodigy 120 points
Part Number: BQ27426
Other Parts Discussed in Thread: GPCCHEM,

Hello, 

We used  the Fuel gauge IC BQ27426 in our project. We config the battery chem id and other parameter as below:

#define BATTERY_VOLTAGE_FULL 4200 // Cell voltage (fully charged) [mV]
#define BATTERY_VOLTAGE_EMPTY 3000 // Cell voltage (empty) [mV]
#define BATTERY_CAPACITY_NOM 2500 // Nominal capacity [mAh]
#define BATTERY_DESIGN_ENERGY 9250 // Design Energy (capacity * 3.7) [mWh]
#define BATTERY_CURRENT_CHG 1250 // Charge current (choose 0.5C) [mA]
#define BATTERY_CURRENT_DSG 1250 // Discharge current (choose 0.5C) [mA]
#define BATTERY_CURRENT_CHGTERM 125 // Charge termination curr. (0.05C) [mA]
#define BATTERY_TAPER_RATE 200 // Taper Rate(capacity*10/125) [.1Hr rate]

But now, if we use a new battery, then we read the SOC of the new battery from the fuel gauge. There is so big gap about the new battery with real battery capacity?

Do we need more configuration for this IC? 

Best Regards,

Mike Song

  • 0
    TI__Guru* 76230 points

    Hi Mike

    When using this gauge, the first step is to run the test outlined in our online tool gpcchem to determine if this gauge is suitable for your cell. If it is suiable, then after configuration you need to extract and store a gmfs file in a none-voltaile incase if power gets cutoff from the chip so it can be able to restore gauging accuracy. You need to periodically store qmax and ra tables to enable accuracy of the gauge. It is also preferable to run a learning cycle

    pls see the quicks start guide for this device in its product folder

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 120 points

    Hi Onyx,

    Thanks for your response.

    We have selection the gauge bq27426 and the product board has been finished, and now selection suitable gauge need more time.

    the bq27426 gauge has three built-in battery profiles;

    • (1202) profile should be used for lithium battery with 4.2-V maximum charging voltage.
    • (3230), (default) profile, should be used for lithium battery with 4.35-V maximum charging voltage.
    • (3142) profile should be used for lithium battery with 4.4-V maximum charging voltage.

    Our battery with 4.2V maximum charing voltage. So we configure the chem id : 1202.

    and other battery parameters as below:

    #define BATTERY_VOLTAGE_FULL 4200 // Cell voltage (fully charged) [mV]
    #define BATTERY_VOLTAGE_EMPTY 3000 // Cell voltage (empty) [mV]
    #define BATTERY_CAPACITY_NOM 2500 // Nominal capacity [mAh]
    #define BATTERY_DESIGN_ENERGY 9250 // Design Energy (capacity * 3.7) [mWh]
    #define BATTERY_CURRENT_CHG 1250 // Charge current (choose 0.5C) [mA]
    #define BATTERY_CURRENT_DSG 1250 // Discharge current (choose 0.5C) [mA]
    #define BATTERY_CURRENT_CHGTERM 125 // Charge termination curr. (0.05C) [mA]
    #define BATTERY_TAPER_RATE 200 // Taper Rate(capacity*10/125) [.1Hr rate]

    Could you help us to check the gauge bq27426 is suitable for us?

     Thank you very much!

    Best Regards,

    Mike Song

  • 0 in reply to Mike#
    TI__Guru* 76230 points

    Hi Mike

    pls listen to what i am saying and you will save your self considerable time. The fact that the default chem id is 4,2V doesn't mean that the gauge is suitable for your cell. You need to run the test listed in our online tool gpcchem to determine if this is the right gauge you ought to be using. If it isn't, we can't fix what is broken because your gauge in the first place is fundamentally not the right device.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 120 points

    Hi Onyx,

    Got it. Thanks. By the way, the chip is recommended by FAE of TI. And now,  we already used in our product and trial produced 400 pcs.

    Best Regards,

    Mike Song