• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 578 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ76940: Sending balancing FET command through bq78350-r1

Felipe Marques
Prodigy 230 points
Part Number: BQ76940
Other Parts Discussed in Thread: BQ78350, BQ78350-R1, TIDA-00449

Hello,

We are developing a battery module which employs bq76940 + bq78350 + MSP430 in LiFePO4 battery energy storage system. After this thread (e2e.ti.com/.../2471248, we did not have the results as expected, even changing some balancing parameters. Then, we would like try an algorithm made by ourselves in order to improve balancing, minimizing battery capacity loss. 

For this task, we need to command manually all balancing FETs through bq78350-r1. For this reason we have some doubts:

1-) Reading bq78350-R1 technical reference, we assume ManufacturerAccess() could be used to control balancing FETs. However, we did not find any command to accomplish this control. Is it really feasible control those FETs trough bq78350?

2-) If it is not feasible, this control should be accomplished directly through I2C interface by MSP430 controller, in my opinion. Is there any issue related on this circuit? We are worried it may have some data collisions, because the MSP430 e bq78350 may want access bq76940 at same time.

3-) If you need to access AFE trough MSP, do you have a sample code? I read a application note related to this topic, but, I have found any source code on website.

Thank you in advance.

Best regards,

  • 0
    TI__Guru 54715 points
    Hi Felipe,
    1. The bq78350-R1 does not have away to force balancing. If used it controls the algorithm. It does not allow you to write to balance registers.
    2. The bq78350-R1 does also not allow you to set the AFE registers directly. If it finds registers which are not as it set them it will consider it a fault and change the registers again. It may go into a fault.
    3. The way to control balancing would be to use the MSP430 as the battery controller to replace the bq78350-R1. TIDA-00449 is an example of that type system. You would need to provide gauge functions. The bq78350-R1 does allow you to turn off balancing, but not to do your own.
  • 0 in reply to WM5295
    Prodigy 230 points
    Hello WM5295,

    Thank you for the quick reply. Your answers were very enlightening, mainly the second one.

    Just one more question regarded to sample codes. Do you have any sample code for bq76940, so I could speed up development?
  • 0 in reply to Felipe Marques
    TI__Guru 54715 points
    Hi Felipe,
    The TIDA-00449 is believed to be easily modified for fewer or more cells in the family of parts. There is the CRC sample code www.ti.com/.../sluc583 in the bq76940 product folder Tools & software tab if it is helpful.