BQ40Z50-R2: IT Algorithm, Coulomb counter

HJ_KIM

Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z50, BQSTUDIO

Tool/software:

Hello.
We are designing drone batteries using BQ40Z50-R2.
In some cases, drones use more than 40A when using Sense Resistor as 1mohm, and in this case, I wonder if it is applied to IT algorithms.
Max values for Gas Gauging - State - Avg I Last Run and Avg P Last Run are 32.768A and 327.67Wh respectively. If so, I was wondering if bq40z50-r2 can't be used for drones using 40A or if it's applicable to IT algorithms up to 100A since it's -0.1V to 0.1V, which is the input voltage spec for Coulomb counter.

9 months ago

0 Anthony 9 months ago

TI__Mastermind 28440 points

Hello,

Using a current value greater than 32A is possible for bq40z50, however the sense resistor and parameters within the gauge would need to be scaled to accommodate for the change.

Regards,

Anthony

0 HJ_KIM 9 months ago in reply to Anthony

Intellectual 485 points

Hello, thank you for your response.
Do you mean to reduce the sense register and scale the value used in Bqstudio (ex. 0.5mOhm)? For example, if the current value is reduced by 3~5 times, the resolution will be lowered and the IT algorithm calculation will be inaccurate. Is it right?
And our product uses 40~50A (typ.) of current, and in this case, I would appreciate it if you could tell me whether it is better to use 1mOhm of Sense Resistor or 0.5mOhm.

Best Regards,

0 Anthony 9 months ago in reply to HJ_KIM

TI__Mastermind 28440 points

Hi HJ,

The Vsense of the SRP/SRN pins have to be kept between +/- 100mV, so 1mOhm should be functional. However, the current register in bqStudio will only read up to 32A, so the device values will need to be scaled. The thread below has more information on current scaling:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/550004/bq40z50-r1-max-current#:~:text=How%20to%20Calibrate%20for%20Current,entered%20as%20the%20actual%20current.

Regards,

Anthony

0 HJ_KIM 8 months ago in reply to Anthony

Intellectual 485 points

Oh, thank you very much, Anthony

Have a nice day!

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BQ40Z50-R2: IT Algorithm, Coulomb counter