• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 284 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.

BQ40Z50-R2: ASCC Short Circuit During Charge - Threshold Value

Joseph DeWitt
Intellectual 320 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQSTUDIO, BQ40Z50

Tool/software:

Hi,

I'm preparing to perform a learning cycle and one of the recommendations is to set an appropriate ASCC - Short Circuit During Charge Threshold value.

Upon accessing the Data Memory - Protection menu in BQStudio the threshold value that can be set is in hex units and is currently set at 45. I'm honestly not sure where this value originally came from. Perhaps its a default value.

My interpretation is that based on Table A-4 there is a voltage value that corresponds to a hex value and that the current value at which the trip will occur is defined by the following equation:

Current = SCC Threshold / Rsense

Therefore for hex setting 0x00 which has a corresponding voltage value of 22.2 mV we have the following correlation

Trip Current = 22.2 mV / 0.001 R = 22.2 Amps where 0.001 is the resistance of Rsense in the BQ40Z50 BMS.

This seems very high.

Is this understanding of how to set the trip current based on the hex value and Table A.4 correct?

How do I input 0x00 into the Protection - ASCC - Threshold table? For 0x00 do I type in 0x00? Or just 00?

What is also confusing to me is that you can also set OCC1 and OCC2 in the Data Memory - Protections table which are the Overcurrent in Charge 1 and Overcurrent in Charge 2 and have mA values that can be inputted. This is much more clear to in terms of setting a current value at which a trip will occur. 

Which method is the correct method for setting the trip current in charge? Using ASCC or OCD1 and OCD2?

Any feedback you can provide would be appreciated.

Best regards,

Joe DeWitt

  • 0
    TI__Mastermind 28480 points

    Hi Joe,

    Joseph DeWitt said:
    Upon accessing the Data Memory - Protection menu in BQStudio the threshold value that can be set is in hex units and is currently set at 45. I'm honestly not sure where this value originally came from. Perhaps its a default value.

    I believe the default value for this register is typically 0x77.

     

    Joseph DeWitt said:

    Is this understanding of how to set the trip current based on the hex value and Table A.4 correct?

    How do I input 0x00 into the Protection - ASCC - Threshold table? For 0x00 do I type in 0x00? Or just 00?

    Your understanding here is correct. For the threshold, the easiest way to make this change is to convert to binary and change the individual bits:

    0x45 = 0100 0101

    Since the SCCV refers to bit 2-0, and you are looking to change this to 0x00, you would need to replace bits 2-0 with 0s.

    0100 0000 = 0x40.

    The same can be done with bits 4 - 7 if you are looking to change the delay.

    Joseph DeWitt said:

    What is also confusing to me is that you can also set OCC1 and OCC2 in the Data Memory - Protections table which are the Overcurrent in Charge 1 and Overcurrent in Charge 2 and have mA values that can be inputted. This is much more clear to in terms of setting a current value at which a trip will occur. 

    Which method is the correct method for setting the trip current in charge? Using ASCC or OCD1 and OCD2?

    I believe the main difference between the ASCC and the OCC protections is the fact that ASCC is a hardware based protection with a latch, with OCC being a firmware based protection. The OCC protections also have a smaller range of when they can be triggered, having a max settable current of around 32A. The ASCC can be set higher than this.

    Regards,

    Anthony

  • 0 in reply to Anthony
    Intellectual 320 points

    Hi Anthony,

    Thank you for the response.

    Given that the units in the Protections - ASCC - Threshold table are in hex should I simply input 0x77 for the ASCC threshold value? Or do I need to convert to binary and input 01110111?

    Thanks in advance for your guidance.

    Best regards,

    Joe DeWitt

  • +1 in reply to Joseph DeWitt
    TI__Mastermind 28480 points

    Hi Joe,

    The threshold can be inputted as the hex value.

    Regards,

    Anthony

  • 0 in reply to Anthony
    Intellectual 320 points

    Thanks Anthony, I appreciate your guidance.

    Best regards,

    Joe DeWitt