BQ40Z50-R2: Problem with GPCRB tool

Hello Iwaszkiewicz,

Did you use the correct chemID ? Your loaded voltage is greater than OCV at low temp since your chemID was not matched with your cell. So, GPCRB can't calculate resistance value.

Did you get a matched chemID from TI or GPCChem ?

Hi Jasper,

Yes, chemID is correct, I received srec with preprogrammed chemistry from TI support, and I worked with that file all the time.

How big the voltage difference is ?

We can't tell how big voltage is since the tool calculated loaded voltage > OCV at some points. Do you need GPCRB data for Rb tweak ?
Would you re-test it as followings. GPCRB data only needs Relax - Discharge - Relax data.

Charge to full at 25C
Wait over 2 hours until Voltage is stable ( < 4uV/Sec)
Discharge under your test condition if you need thermal model value like Temp K or Temp a
Wait over 5 hours unti Voltage is stable

Charge to full at 25C
Change the temp to low
Wait over 2 hours until Voltage is stable ( < 4uV/Sec)
Discharge under your test condition.
Wait over 5 hours unti Voltage is stable

Hello Jasper,

I have data to GPCRB, It is on 4721.GPCPackaged.zip above.

I was performing that procedure as you wrote, I used thermal chamber and charge/discharge rates as in the target device.

According to your log file(lowtemp.csv), you charged the cell at low temp. Please, correct me.

15028.89	13182	4.7	0
15034.89	13526	4.7	426
15040.89	14110	4.7	1364
21491.26	16781	6.1	61
21497.26	16791	6.1	59
21503.26	16756	6.1	0

I recommend you to test under constant load condition at both low and room temp if GPCRB still failed after charging the battery in room temp.

The calculation says your chemID might not be matched but you confirmed your chemID was correct. It is hard to say where negative resistance was detected under dynamic load condition. So, I need loaded curve under constant load condition to compare it with OCV curve.

Hi Jasper, thank you for reply

Yes, I charged in low temperature because my system has high thermal capacity and cooling down would take many hours.

I can use constant current load, but GPCRB instruction says that device load profile will give best results.

Is there any way to check if chemistry in srec is correct? Check that it has the right ID number?

Generally SOC behaves correctly, but in some conditions, (low temp, high current) could behave better, that is why I'm performing optimisation.

Hi dMax

I do not have a test stand anymore, so Im not able to repeat that procedure.
SOC accuracy is good, so I will stay with actual settings.