BQ4050: GPCCEDV: CEDV coefficients EDVR0 from GPC report out of bqstudio's value range?

Tom Li

Part Number: BQ4050
Other Parts Discussed in Thread: BQSTUDIO, BQ78350-R1, GPCCEDV

Hi,

I have received the GPC report for the discharge logs of a BQ4050 CEDV Gas Gauge with two Lithium Ion (LG INR18650-MJ1 3500mAh) cells placed in series. The CEDV parameters from the report read as follows:

EMF   5968
EDVC0   101
EDVC1   0
EDVR1   1
EDVR0   128143
EDVT0   4452
EDVTC   11
VOC75   7871
VOC50   7617
VOC25   7504

I entered the parameters in bqstudio but got an error for EDVR0 after trying to enter 128143 in the R0 field under (Gas Gauging --> CEDV cfg):

"Value is beyond maximum value defined for parameter."

I have checked the TRM (https://www.ti.com/lit/ug/sluuaq3a/sluuaq3a.pdf?ts=1693811569270) and the maximum value allowed for R0 is 65535.

I'm wondering if I'm interpreting the CEDV parameters from the report correctly (like suggested here for the BQ78350-R1 gauge: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/763132/bq78350-r1-capacity-learning/2820936?tisearch=e2e-sitesearch&keymatch=edvr0%2520r0#2820936)

EMF         -->    EMF
EDVC0    -->    C0
EDVC1    -->    C1
EDVR1    -->    R1
EDVR0    -->    R0
EDVT0    -->    T0
EDVTC    -->    TC

The TRM also states (section 6.4.1):

"R0 is the first order rate dependency factor stored in EDV R0 Factor/EDV2."

I'm not using a fixed EDV2 in my configuration (EDV_CMP=1). If above formula is correct, how can I determine the dynamically calculated EDV2?

Thank you in advance.

Tom

over 2 years ago

0 Tom Li over 2 years ago

Prodigy 20 points

I have just taken another measurement. I have used the same log file for all 6 measurements, since I do not have access to a temperature chamber at the moment. The value for EDVR0 is again that high 124605 (see the attached report).3681.GPCPackaged-report.zip

0 Shirish over 2 years ago in reply to Tom Li

TI__Guru 57697 points

Hello Tom,

A temperature chamber is required. Submitting the same log for all temperatures will give bad results

0 Tom Li over 2 years ago in reply to Shirish

Prodigy 20 points

Hello Shirish,

yes, I want to do the final measurements inside a temperature chamber.

If EDVR0 corresponds to bqstudio's R0 then shouldn't the GPCCEDV online calculator report the best set of parameters that can actually be programmed into gauges? I would consider this a bug.

Best regards,

Tom

0 Shirish over 2 years ago in reply to Tom Li

TI__Guru 57697 points

Hello Tom,

I will assign this thread to an expert. I think EDVR0 128143 seems to be very high

0 Wyatt Keller over 2 years ago in reply to Shirish

TI__Guru** 105760 points

Hello Tom,

Please only submit data to the tool in the format specified by the GPCCEDV guide, if you submit different data sets this can cause problems with how the tools calculates the coefficients. EDVR0 of 128143 is much too high.

Can you attach the data you submitted to GPCCEDV?

Sincerely,

Wyatt Keller

0 Tom Li over 2 years ago in reply to Wyatt Keller

Prodigy 20 points

Hello Wyatt,

please have a look at the data submitted to GPCCEDV in the attachments. I used bqstudio to generate the package.

As mentioned earlier I used the same log file for all 6 measurements in order to get familiar with the process leaving GPCCEDV no room for temperature and load compensations.

Kind regards,

Tom

dshg_cedv_r0_high1.zip dshg_cedv_r0_high2.zip

0 Wyatt Keller over 2 years ago in reply to Tom Li

TI__Guru** 105760 points

Hello Tom,

The tool requires the temperature and load variations in order to calculate the coefficients, so I would disregard the GPCCEDV report values until the steps in the guide are followed. I would also make sure to delete the header information when you submit the logs (with the date and gauge/bqstudio information).

Sincerely,

Wyatt Keller

0 Tom Li over 2 years ago in reply to Wyatt Keller

Prodigy 20 points

Hello Wyatt,

thank you, yes the missing variations may be the root cause of the problem although I find it questionable that the GPCCEDV tool is able to report parameters outside of the possible value ranges. The only guarantee I have that this doesn't also occur when taking measurements inside the temperature chamber is that apparently no one else seems to have reported similar problems.

Kind regards,

Tom

+1 Wyatt Keller over 2 years ago in reply to Tom Li

TI__Guru** 105760 points

Hello Tom,

I have not seen this issues before, but I have also not seen data being submitted with no temperature variations. If the coefficients are still abnormal after all data submitted follows the guide, then we can look into this further.

Sincerely,

Wyatt Keller

0 Tom Li over 2 years ago in reply to Wyatt Keller

Prodigy 20 points

Hello Wyatt,

that's fair enough, I'm going to do the measurements inside a temperature chamber following the guide.

Kind regards,

Tom

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BQ4050: GPCCEDV: CEDV coefficients EDVR0 from GPC report out of bqstudio's value range?