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Original question:

BQ27426: Chemistry tab does not appear in bqstudio

BQ27426: BQ27426 Configuration

Akilarasan R
Prodigy 230 points
Part Number: BQ27426
Other Parts Discussed in Thread: BQSTUDIO, GPCCHEM, , BQ27Z561

Hi,

Here below are my battery spec,

Lithium Ion INR18650 M36T 12.50Wh Specs
Nominal energy 12.50Wh
Minimum energy 12.10Wh
Nominal voltage 3.63V
Standard charge current 1000mA (0.3C)
Charge end voltage 4.2V
Charge cut-off current 50mA
Max. charge current 1000mA (0.3C) at 0-24C, 2330mA (0.7C) at 24-50C
Max. discharge current 5000mA

My doubt is that what are the things I have to do to configure battery gauge. Like what are the registers I have to configure to set battery voltage and battery capacity. Also how I can do it? 

After setting those, I can give standard commands through I2c  and I can get my battery status information?.  

  • 0
    TI__Mastermind 27321 points

    Hello,

    The first step is to ensure your battery chemistry is compatible with one of the chemistries in the TRM and other documentations. Se below. You can either match them by looking at the characteristics or using the GPCCHEM tool which will tell you which chemistry IDs from our database is more similar to the cell chemistry you are using. I suggest to use the tool.



    Please see the Quick Start guide for basic parameter configurations. After matching you cell. a learning cycle is required.

    Akilarasan R said:
    After setting those, I can give standard commands through I2c  and I can get my battery status information?.  

    Correct, but the gauge needs to know about the battery cell first. Ensure you do the learning cycle first. See this App note for communications.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 230 points

    Hi,

    Here are my doubts:

    1. Our battery's maximum charge voltage is 4.2V. So, I can use 1202 chemID, right?

    2. What do you mean by learning cycle?

    3. Our gauge's I2c will be connected to FPGA. From datasheet, I understood that we have to configure gauge through I2C. Mostly, I have to configure (1) Design Capacity, (2) Design Energy, (3) Terminate Voltage, and (4) Taper Rate values of our battery. Is that right?

    4. At last, can we achieve configuration without use of bqstudio software?

  • 0 in reply to Akilarasan R
    TI__Mastermind 27321 points

    Hello,

    1- For two battery chemistries to be compatible, there's more specs to look at than just the max charge voltage. Each chemistry ID in our data base has a unique OCV table. I suggest to either get the exact cell for chemID 1202, or use the GPCCHEM tool to match the cell you are using with one of our database.



    2- Please see this start guide for BQ-products, it describes the learning cycle.

    3-  The gauging parameters needed are described in Section 2 of this App Note

    4- You can configure the device without bqStudio software. It is easier to use the software. Reference to the Gauge Communication App note. 

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 230 points

    Hi Jose,

    I got to know that this gauge is a ROM gauge, it has pre-programmed chemistry IDs that cannot be changed. Is it true?

    If it is true, Is there a way I can use this gauge with my battery or I have to change the gauge IC?

  • 0 in reply to Akilarasan R
    TI__Mastermind 27321 points

    Hi Akilarasan,

    Correct, ROM gauges come with pre-defined ChemID stated in datasheet. 

    You have two options:

    1- Obtain the same cell chemistry defined as chemID = 1202in my previous reply.
    2- Purchase a flash gauge. Flash gauges allows you to program any chemistry. I suggest BQ27z561-R2 without protections and BQ27z746 with integrated protections.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 230 points

    Hi Jose,

    1. I need a clarification, basically chemistry id will define what?

    2. Also, I chose this gauge because it was mentioned that this IC will support 4.2V battery as 4.2V pre-programmed profiles were available. they didn't mention about chemistry ID and all.

    3. I went through  BQ27z561-R2 and  BQ27z746  datasheet and their pin functions are little bit different than BQ27426. Is there any flash gauge which is similar to BQ27426.

  • +1 in reply to Akilarasan R
    TI__Mastermind 27321 points

    Hi Akilarasan,

    1- ChemID defines the OCV and internal resistance of the battery across low, room, and high temperature. The gauge uses this information to run capacity predictions.

    2- "4.2V pre-programmed profiles were available" is essentially pre-programmed chemistry profiles. The 1202 ID for example has a highest OCV voltage of 4.2V. This does not mean you can use any 4.2 Volt battery. You will need to either get the same listed cell in the picture I provided or use the GPCCHEM tool to find the most matching cell in the database and we can see if it compatible with ChemID 1202. Essentially we are looking at OCV curve compatibility.



    3- There's no such device pin to pin compatible with the BQ27426. The BQ27z561 is a flash gauge option for 1S devices, this does not mean they will share the same pins. They are different devices.

    Regards,
    Jose Couso