BQ41Z90EVM: Inconsistent CompRes Value

Pooja Agarwal

Prodigy 35 points

Part Number: BQ41Z90EVM

Tool/software:

Dear Texas Instruments Support Team,

I am encountering unexpected inconsistencies in the Cell CompRes values. The specific issues are:

At one instance, the Cell2 CompRes value is 0.
There is a significant jump in the CompRes values of different cells. ( For eg., Cell 1 CompRes value at different instants => 54,22,16 mOhm)
Additionally, I found that the Cell4 CompRes value was negative at one instant.

I would appreciate insights into possible reasons for these fluctuations and any factors that might influence such behavior.
Thank you

3 months ago

0 Diego 3 months ago

TI__Mastermind 25915 points

Hi,

You are using real cells to power the EVM, correct?

Can you provide a log file of these values changing over time?

Where these 3 screen shots taken with the same cells in the same environment?

Regards,

Diego

0 Pooja Agarwal 3 months ago in reply to Diego

Prodigy 35 points

Hello Diego,
Thanks for your time.
Yes, I'm using real cells of 4S3P configuration.
Yes, these screenshots are taken with the same cells and in the same environment.
I am attaching the log file
Thank You
Discharging cycle (for resistance).log

0 Diego 3 months ago in reply to Pooja Agarwal

TI__Mastermind 25915 points

Hi,

Thanks for the files. Looking at CompRes for cells 1-4, they all show the same general behavior, I believe this behavior is just due to the nature of the cells.

Regards,

Diego

0 Pooja Agarwal 2 months ago in reply to Diego

Prodigy 35 points

Hello Diego,

Thanks for the explanation!

Given the high inconsistency in these values, is there another parameter—such as an average—that we could use to determine the resistance value?

Regards,

Pooja

0 Diego 2 months ago in reply to Pooja Agarwal

TI__Mastermind 25915 points

Hi Pooja,

There is not an average register for this parameter however I would expect this behavior to be consistent across cycles. These values can be averaged by hand to get a rough estimate.

Regards,

Diego

0 Pooja Agarwal 2 months ago in reply to Diego

Prodigy 35 points

Hi Diego,

The behavior across cycles appears inconsistent. While manual averaging can provide a rough estimate, the discrepancies between both graphs suggest that additional factors may be influencing the parameter. I have attached the graph of one more discharge cycle. In the last cycle, the log of which I attached, the discharging current was 8A, but in this recent cycle, the discharge current is 9A.

Could you please help explore this further

Regards,

Pooja

0 Diego 2 months ago in reply to Pooja Agarwal

TI__Mastermind 25915 points

Hi Pooja,

Please allow me some time to look into this.

Regards,

Diego

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BQ41Z90EVM: Inconsistent CompRes Value