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BQ35100: Some calibration, chemistry, and measurement questions.

David Fernandez60
Prodigy 200 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO,

Hi there,

I have been reading through the DS & TRM an had a quick look at bqStudio.

1. bq Studio seems to have the Energizer L91 chemistry available to program. Can the bq35100 be program with it for SOH/EOS, or is it limited only to Li-MnO2/SOCl2 chemistries? Is there any other gas gauge that supports Li-FeS2?

2. For calibration, Is there any difference in the conditions to apply for CC offset and Board offset? The TRM only mentions that no current should flow.

3. Is it possible to generate a bqStudio srec file to program a selected chemistry ID from the MCU?

3. The TRM describes several calibration flash areas, specially for temp model. Does the tempcalibration take care of those, or do I need to calculate them in some way?

4. There are several configuration, design, and gas gauge areas in the flash map that is not clear if they need to be programmed in the factory, or if they depend on the chemistry and are supplied by bqStudio some chemistry table that you provide. Thinking about production here.

5. For the accumulator mode, does the chip update the accumulated capacity accounting for the time it has been off? like assuming the last current measured is the standby current? If the host has to do that, is it possible to write back to the updated value from the host to the gas gauge?

Regards

  • 0
    TI__Guru* 76230 points

    1. The gauge can be technically used for any kind of cell. You just need to determine which mode will work right with your cell. Accumulator mode is the best mode that will work with any cell.

    2. Both should be performed. The conditions are the same like you pointed out-no current flow.

    3. The temp calibration takes care of that. Except you use a non-10k thermistor, then you will need to calculate the thermistor coefficients.

    4. Once you configure the gauge, you extract a golden srec  or flashstream file that will be used for mass production. You do not need to program individual sections.

    5. No.It is assumed that you know the current flow in your system which should be really low when the chip is off, and account for that in your host. No, you can't write the updated value to the gauge.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 200 points

    Hi Onyx,

    Thanks for answering.

    I would like you to be a bit more specific on a few points though.

    In your answer:

    For #1, I know the accumulator mode will work with any cell, but given that bqStudio offers the Energizer L91, if I program it into the bq35100, which of the SOH or EOS modes will work better with it?

    For #3, is there some documnet that explains how to calculate them, or at least shows the model formula using the coefficients?

    For #4, I take I should still calibrate each one after the srec file is re-programmed into a new device.

    Regards

  • 0 in reply to David Fernandez60
    Prodigy 200 points

    Hi there,

    Anything on the above questions?

    Regards

  • 0 in reply to David Fernandez60
    TI__Guru* 76230 points

    hi David,

    I looked up the data sheet for the cell, at  i see the OCV curve is not flat. That said, the gauge will also support the device in SOH mode as well. The caveat is the  gauge needs to be powered by atleast 2.4V, so you will need to a min of 2 cells or you use a form of boost converter to power the chip off 1 cell. All three modes, EOS, SOH and accumulator modes should  work fine, as long as the caveat mentioned above is taken into consideration.

    See attached excel sheet. Use the pack side tab if you absolutely need to use a different thermistor other than the 10K ntc recommended. I would not recommend you use a different one though.

    2804.ntc_calc.xlsx

    You don't need to calibrate each one. You can take the average calibration values of 20 units and program on one unit and then extract a single file which will be your golden file.

    i hope this helps.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 200 points

    Hi Onyx,

    Thanks for getting back to me in the end.

    Regards