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BQ35100: BQ35100 battery characterization

Gabiel S.
Prodigy 130 points
Part Number: BQ35100
Other Parts Discussed in Thread: GPCCHEM

Hello,

we want to use a BQ35100 (EOS-Mode) in our system to monitor our LTCs, which are FANSO ER18505M.

This battery is currently not characterized, so I cannot choose it in the Chem-ID list.

From other forum threads, I read, that the correct Chem-ID is crucial, mainly for SOH measurement. But can you tell me, what exactly would be the expectation, if we used a "similar Chem-ID"?

Further I want to know what makes batteries similar to each other. What are the parameters to compare? size, capacity, max load current?

More interesting questions:

What are the requirements for TI to characterize a new battery type?

How long would the characterization take approx.?

What are the costs?

Thanks for your answers!

Kind regards

Gabriel

  • 0
    TI__Guru** 105760 points

    Hello Gabriel,

    You cannot use another similar cell's chem ID for primary batteries, we do not have a GPCCHEM for primary cells.

    As stated in the TRM the SOH while in EOS mode may not be reliable even with the chem ID.

    You can generate your own Ra table using the application note: https://www.ti.com/lit/pdf/sluaal7

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hello Wyatt,

    thanks for your answer.

    So for this "home characterization" it is not needed to configure any chem ID, is this correct?

    Regarding production spread of the cells, what is your recommendation of the number of cells to be charcterized?

    Kind regards

    Gabriel

  • +1 in reply to Gabiel S.
    TI__Guru** 105760 points

    Hello Gabriel,

    That's correct, you can essentially generate your own Ra table and program it to the gauge to correlate the resistance with SOH %.

    The more cells tested the better confidence you can have in the results. Starting with 3 in case there are issues with 1 or 2 would probably be optimal.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Wyatt,

    okay, thanks again for your quick help!

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Again,

    I just read this thread here:

    e2e.ti.com/.../bq35100-bq35100-battery-characterization

    In this thread, the TI__Guru states, that in EOS mode, the correct Chem-ID is not needed at all - the default Chem-ID can be used.

    Now I am pretty confused. Can you tell me what exactly the Chem-ID is needed for?

    A little more background:

    In our application, we need a way to estimate, when our battery is considered empty. In the easiest scenario, this might be done using an SOH percentage, which however needs an exactly matching Chem-ID.

    It could also be an alert, that is generated early enough, that the system can react to it -> like 2 weeks before EOS under normal operation, or so.

    As far as I understand Onyx Ahiakwo, the alert approach (which is basically the EOS-Mode goal) does not need any battery characterization or exact Chem-ID. Is that correct?

  • 0 in reply to Gabiel S.
    TI__Guru** 105760 points

    Hello Gabriel,

    Yes that is correct, Onyx is referring to just the alert which does not require a specific chem ID or Ra table updates. All you need to do is set the resistance filters based on the example in the app note I linked previously.

    If you want to try to get SOH percentage data you will need to either generate the Ra table manually or use the exact match for the chem ID and the cell you are using. But as mentioned SOH % in EOS mode may not be reliable until closer to the end of discharge when Ra begins to increase.

    Sincerely,

    Wyatt Keller