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BQ78350: A microcontroller instead of the BQ78350.

Devis Fracassi
Prodigy 185 points
Part Number: BQ78350
Other Parts Discussed in Thread: BQ76930, , BQ76940, BQ34Z100-G1, BQ76952, TIDA-010030

Dear,

for an ebike Li-Ion battery, we have designed a BMS using the BQ76930 + BQ78350 and also a microprocessor ARM-M0.

We are interested to evaluate the Pro and Cons to remove the BQ78350 and implement its functions in the ARM-M0.

We will have a more compact and a little bit cheaper BMS.

Perhaps, is there any "Application Note" that describe how to implement the BQ78350 in a microprocessor, or an example of "C code functions" ?

Instead of the BQ78350, is there any more suitable device (more compact, cheaper, simpler, ... considering the board has also a microprocessor) ?

Thanks for any your suggestion. Regards.


Devis

  • 0
    TI__Guru* 81035 points

    Hi Devis,

    The BQ769x0 monitor family is commonly used both with and without the BQ78350 controller. While we cannot help you implement the functions of the BQ78350 in C code (the BQ78350 performs many functions with are proprietary), I can highlight some of the considerations below.

    Using only a microcontroller: This offers the maximum amount of flexibility since you control all of the decision making. For example, if you have special functions for your system that are not accounted for in the BQ78350 firmware, you can easily make the changes you need to your microcontroller firmware. If accurate gauging is not a need for your system, 

    Using the BQ78350: The BQ78350 is a controller specifically designed to operate with the BQ769x0 family and offers the gauging feature plus many additional software-based protections. This is convenient for the user with less experience since it handles all of the interactions with the BQ769x0, checks and clears status registers, etc. And of course if gauging is important, this may be the main reason to use this option.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 185 points

    Hi Matt,

    I really appreciated your support.

    Due to some ebike functions (communication, other ...) we must use a microcontroller.

    - So, I understand there is no any TI Application Note about the 769x0 managed by a microcontroller. Correct?

    - To switch off the battery output, we shutdown the BQ78350 at every battery/ebike switch off. So there is a GG reset at every turn-on of the battery. Despite there is no charge/discharge data in the GG memory, does the BQ78350 performs accurately the gauging function ?

    - In your opinion, for an ebike battery, is the BQ78350 correct to use or are there any newer / simpler GG more specified?

    Thanks. Regards.


    Devis

  • +1 in reply to Devis Fracassi
    TI__Guru* 81035 points

    Hi Devis,

    There is no specific application note on microcontroller programming for the BQ769x0, but there are basic code examples in the ti.com product page under the software development section (https://www.ti.com/lit/zip/sluc583 ). There is also TI Reference design using the BQ76940 with the BQ34Z100-G1 gauge: https://www.ti.com/tool/TIDA-010030 So the BQ34Z100-G1 is also an option for an Impedance Track gauge that operates independently from the monitor.

    The BQ78350 is completely powered down during Shutdown, so upon waking it can only estimate the SOC from the cell voltages. This thread may be helpful:

    https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/877837/bq78350-r1-how-to-read-capacity-after-shutdown

    There is also the BQ76952 battery monitor family. This monitor has many more advanced features. Many users are using this in combination with the BQ34Z100-G1 gauge (similar approach to TIDA-010030). This may be a better option. The BQ76952 also has code examples available - there are also many training videos here: https://training.ti.com/bq76952-and-bq76942-battery-monitors 

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 185 points

    Really thanks Matt.

    Bye.


    Devis