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BQ40Z80EVM-020: SOH calculation for Lithium Titanate(LTO) battery

adam sun
Prodigy 180 points
Part Number: BQ40Z80EVM-020
Other Parts Discussed in Thread: BQ40Z80, GPCCHEM

Hi~

1. We use 7 strings of LTO batteries to make BMS. Can we set soh in bq40z80?

2. If yes, where should I start?

Best Regards,

Adam

  • 0
    TI__Mastermind 42060 points

    Hello Adam,

    1. We use 7 strings of LTO batteries to make BMS. Can we set soh in bq40z80?

    Yes, the BQ40Z80 supports SoH.

    2. If yes, where should I start?

    You can start with the Technical Reference Manual(Section 7.7) to learn more about SoH in the BQ40Z80.


    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 180 points

    Luis H. S. said:

    Hello Adam,

    1. We use 7 strings of LTO batteries to make BMS. Can we set soh in bq40z80?

    Yes, the BQ40Z80 supports SoH.

    2. If yes, where should I start?

    You can start with the Technical Reference Manual(Section 7.7) to learn more about SoH in the BQ40Z80.


    Best Regards,

    Luis Hernandez Salomon

    Hi~

    Thank you for such a quick reply.

    Are my current steps as follows?

    1. First create the chemical ID and settings.

    2. The first step to operate these, should GAUGE_EN=1 be set first?

    3. Let the battery charge and discharge learning.

    Also, is there a formula for soh calculation in BQ40Z80? Can you describe it?

  • 0 in reply to adam sun
    TI__Mastermind 42060 points

    1. First create the chemical ID and settings.

    Yes. If your cell is not found in the Chemistry Table, use the GPCCHEM tool to find a closely matching chemID. Using the GPCCHEM tool ensures that the learning cycle will not fail.

    2. The first step to operate these, should GAUGE_EN=1 be set first?

    Yes.

    3. Let the battery charge and discharge learning.

    I would suggest you checking the guide How to Complete a Successful Learning Cycle for more information about the learning cycle using the BQ40Z80.

    4. Also, is there a formula for soh calculation in BQ40Z80? Can you describe it?

    I don't believe there is an exact formula. A simple formula would be Full Charge Capacity/Design Capacity. However, the SoH in the BQ40Z80 is calculated by simulating the Full Charge Capacity using the typical current of the application. You can read once again Section 7.7 of the  Technical Reference Manual for information regarding SoH. 

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 180 points

    Hello Luis~

    First of all, I wish you a happy weekend~

    Thank you very much for your assistance, these are very useful information.

    But in the cycle of battery charging and discharging, battery balancing has not started.

    Attached here is the log of my test. Could you please help confirm that there is a problem with the settings in that part?

    Best Regards,

    Adam06180817.rar

  • 0 in reply to adam sun
    TI__Guru 52115 points
    Hi Adam,
    I would suggest you take a look at Chapter 8 Cell Balancing of BQ40z80 TRM to make sure your settings are correct. As we mentioned in the TRM, a field updated QMax (Update Status = 0E) is required prior to any attempt of cell balance time calculation.
    Also, make sure the learning cycle is successfully performed first so that the Update State become 0E.
    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 180 points

    Hi Andy,

    Thank you for your suggestion, I will study the battery balance settings carefully.

    Then charge and discharge the battery.

    Thank you for your assistance~

    Adam