BQ40Z50-R2: Tell me about the changes in SOH and Ra

user5768972

Part Number: BQ40Z50-R2

Tool/software:

Hello everyone.

I am experiencing a strange phenomenon in 40Z50 where I have made a mistake in calibration.

Voltage calibration
Battery voltage：16.671V
Pack Voltage： 16.671V
Cell Voltage: 4.066V
Cell Voltage: 4.066V => 0.1V lower than the real Cell voltage of 4.166V.

Repeated 3 cycles of charging and discharging in this state,
SOH: Initial value 99% ⇒ Decreased to 93
Ra changed about 4 times (at around 50% DOD).

Next, 20 cycles of charging/discharging were repeated without changing any settings.
SOH: 93% ⇒ increased to 98
Ra increased from 4 times to 2 times (at around 50% DOD).

Question 1
Why do SOH and Ra change with calibration voltage (Cell) errors?

Question 2
Why do they return to their original values as the number of cycles is repeated?

best regards.

7 months ago

0 Adrian 7 months ago

TI__Mastermind 37761 points

Hello,

Can you send the data from your testing? I will need to see the dataset to help debug this issue. Can you also send the gg file from the gauge?

Regards,

Adrian

0 user5768972 7 months ago in reply to Adrian

Intellectual 450 points

Hello Adrian.

Please check the file attached.

SREC(cell0.1):Initial Settings
GG_1(cell0.1): GG file when fully charged after initial setup
GG_2(cell0.1): GG file after charging and discharging 3 times
GG_3(cell0.1): GG file after charging and discharging 6 times
GG_4(cell0.1):GG file after charging and discharging 26 times

best regards.

SREC(cell0.1).xlsx GG_1(cell0.1).xlsx GG_2(cell0.1).xlsx GG_3(cell0.1).xlsx GG_4(cell0.1).xlsx

0 Adrian 7 months ago in reply to user5768972

TI__Mastermind 37761 points

Hello,

Please allow me some time to look into this.

Regards,

Adrian

0 Adrian 7 months ago in reply to Adrian

TI__Mastermind 37761 points

Hello,

It is recommend to use the gauge with correct calibration. When the gauge is calibrated then the gauge will have all necessary information to accurate report data like SOH, SOC, and Ra table. The gauge uses cell based termination to determine these values, and if the cell voltages for the cells are not reported accurately then those registers won't report accurately either. Also, it seems that the cells are imbalanced when properly calibrated. It is recommend that the gauge is recalibrated, and then the cells are balanced.

Regards,

Adrian

0 user5768972 7 months ago in reply to Adrian

Intellectual 450 points

Hello

I'm sorry, but...
Question 1
Why do SOH and Ra change with calibration voltage (cell) errors?

Question 2
Why do they return to their original values after repeating the number of cycles?
I have not received answers to the two questions.

Please answer these two questions.

0 user5768972 7 months ago in reply to user5768972

Intellectual 450 points

Can someone please answer this question for me?

0 Adrian 7 months ago in reply to user5768972

TI__Mastermind 37761 points

Hello,

Accurate voltage readings are necessary for accurate SOH and Ra table values. If the voltages are not accurate then there will be error with SOH and Ra table updates. I would recommend reading over this document that explains impedance track: https://www.ti.com/lit/an/slua364b/slua364b.pdf

user5768972 said:
Why do they return to their original values after repeating the number of cycles?

Since voltage reading are not accurate, SOH and Ra table values should be disregarded.

Regards,

Adrian

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BQ40Z50-R2: Tell me about the changes in SOH and Ra