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BQ77915: Battery protect board design

GARETH OU
Guru 11945 points

Part Number: BQ77915
Other Parts Discussed in Thread: BQ76930, BQ76940

Hi

Three boards for battery protection: 

Board A: 6 series, Continue 30A, Peak 50A (2~3sec/10sec)

Board B: Support 14 series / 12 series (Co-layout),

I. Continue 100A, Peak 150A

II. Continue 150A, Peak 300A

Current limit setting by digital interface (I2C) or resistance setting. 

Board C: Support 18 series / 20 series (Co-layout), Continue ?A, Peak ?A

Currently, I found a BQ77915 chip that can be stacked.

I plan to share this chip across these three boards: 

Board A BQ77915 x 2 > 3+3

Board B-14series BQ77915 x 3 > 5+5+4

Board B-12series BQ77915 x 3 > 4+4+4

Board C-18series BQ77915 x 4 > 5+5+5+3

Board C-20series BQ77915 x 4 > 5+5+5+5

 

Additionally, if cell balancing is required, are there any reference designs for BQ77915 stacking?

Alternatively, could you suggest a suitable solution for designing these three boards (Battery Protection + Cell Balancing)?

Please confirm that the following battery series connection is correct. If there are any errors, please correct the attached file and send it to me. Thank you.

BQ77915 serial.xlsx 

  • 0
    Guru 11945 points

    Considering the flexibility of the protection IC, I'd like to modify the solution as follows:

    1. 6S: BQ76930

    2. 12S: BQ76940

    I would also like to ask if this series of protection ICs can operate continuously without an MCU, simply by using TI tool to write the desired parameters, without failing to operate after a power outage and power-on? Thanks,

  • 0 in reply to GARETH OU
    Guru 11945 points

    Hi 

    Could you help check below the BQ77915 schematic and any need to adjust

    Thanks

    Board A

    6 series, Continue 30A, Peak 50A(2~3sec/10Sec)

    Board B

    Support 14 series / 12 series(Co-layout),


    I. Continue 100A, Peak 150A

    II. Continue 150A, Peak 300A

    BMS-6S.pdfBMS-12S_14S.pdf

  • 0
    TI__Expert 3475 points

    Hello Gareth,

    Unfortunately, we do not have a reference design for BQ77915 stacking, but we do have an application note that should help illustrate what the design/implementation should look like. Sharing this below.

    Stacking Implementations with bq77915 (Rev. A)

    The battery series connection shown on the excel appears fine. However, the key part for using a lower cell count with BQ77915 is the configuration of CCFG. Please view Table 7-9 of our datasheet for more information.

    Regards,

    Rohin Nair

  • 0 in reply to GARETH OU
    TI__Expert 3475 points

    Hello Gareth,

    The hardware protection delays and thresholds should be loaded into the device be the host MCU during startup. Any power-on reset even will require the delays and thresholds to be rewritten into.

    Something to note is that the device does have default thresholds and delays which will be loaded into the device RAM open a power-on event.

    Regards,

    Rohin Nair

  • 0 in reply to GARETH OU
    TI__Expert 3475 points

    Hello Gareth,

    Please give me until tomorrow to review the schematic.

    Regards,

    Rohin Nair

  • 0 in reply to Rohin Nair
    Guru 11945 points

    Hi Rohin,

     What do you mean about HW protection delay/threshold? Anything we need to set through MCU?

    Regards

    Gareth

  • 0 in reply to GARETH OU
    TI__Expert 3475 points

    Hello Gareth,

    I am referring to the thresholds and delays for the protections like over-voltage, under-voltage, over-current in discharge, etc. These delays and thresholds can be configured in various registers available in our device.

    For example, the threshold for and over-voltage can be configured in the OV_TRIP register. The delay for an over-voltage can be configured with the PROTECT3 register.

    These registers have default values that will be loaded automatically during power-up. If you would like to have custom thresholds and delays in the device, the MCU will have to write to these registers each time during start-up as there is no way to permanently burn the values into the device.

    Regards,

    Rohin Nair

  • 0 in reply to Rohin Nair
    Guru 11945 points

    Hi Rohin

    Thank you for your explanation.

    Does the schematic need to be adjust?

    Regards