BQ78350-R1: CEDV Data Collection for Gauging Parameter Calculator (GPC)

Hi again,

Enclosed you can find the "package" uploaded in GPC Tool online and the report returned.

4578.GPCPackaged.zip3021.GPCPackaged-report.zip

Hello,

I have fixed the point number 2 of my previous question. It didn't introduced the proper "Number Of Series Cells = 14". Point 1 is still open.

Meanwhile, I've continued my testing without multiplying EMF and EDVR0 value by the number of series cells. So, I've introduced the parameters as they has been reported. Afterwards, with the battery pack fully charged, I've done a "reset" and I've executed a discharging test monitoring all registers, specially RSOC and ASOC. In this test I saw that EDV2 reached when all the 14 cells where around 3,765V (note that nominal cell value is 3,7V). Contsequently, RSOC and ASOC were updated from 38% to 7%. 

Note that I've set the values of EDV 0, 1 and 2 Hold Time to 20s, in order to be completely sure that any kind of noise in cells measurement could affect for premature EDV2 detection. 

Do you have any idea about that is going wrong?

Enclosed you can find he reported CEDV parameters: 5282.GPCPackaged-report.zip

And here you are the log file of discharging test executed afterwards with a graphic result focussed on RSOC: W005_Test#001_EvalParams2o_Package.log

Hi Marco,

The EDVV bit does not apply for the BQ78350. This parameter is present in some other TI battery gauges, but you can ignore it for this device.

I am looking at the log file, and it looks like the PendingEDV column is showing 3665mV - this is what the gauge is watching for to trigger EDV2. It seems a little high since EDV2 should correspond to 7% SOC. Around 100 seconds before the EDV2 is triggered, it does look like the Cell 10 voltage dips by around 100mV for around 20 seconds. It doesn't seem to get as low as 3665mV, but it is pretty close. I wonder why only this voltage is dipping - do you have the recommended 10uF and 1k filter components on the VC10X and VC5X pins?

I also recommend setting the EDV_EXT_CELL bit in CEDV Gauging Configuration. This will use the average cell voltage for triggering EDV2. It may also be good to set the VFLT_EN bit in the same register. There is also an Overload Current parameter that can be used to ignore large short pulses.

I looked at the report from the GPCCEDV tool and it looks like the error is pretty large. Can you send the log files so I can take a quick look at what might be causing this?

Best regards,

Matt

Hi Matt,

I'm going revise on the hardware about the recommended 10uF and 1k filter components on the VC10X and VC5X pins.

Meanwhile, enclosed you can find the files used to generate the report. How could I reduce the "deviations for this set of parameters given" by the report? There is a deviation of 9,48% in lowtemp_highrate test. I've tried to reduce this deviation by repeating the test, and I've obtained similar deviation result.

GPCPackageFromBqStudio.zip

Hi Marco,

I see some issues in the log files. One issue is that the current turns off and on during the log (it appears the under-voltage protection is triggering which is opening the DSG FET). Another issue is the the logs are not all reaching the cell termination voltage you defined (3000 mV). They are stopping much earlier. 

You want to make sure your protections are configured a little looser while collecting these log files. The log files are showing the characteristics of the battery cells themselves, so the gauge is not even required - it is just helpful to log the voltage, current, and temperature. 

I also notice the External Average cell voltage is not showing correctly in the log files. You may need to calibrate this parameter to get the correct reading.

Best regards,

Matt

Hi Matt,

Thank you so much for your answers.

First of all, as you say, the values of 10uF and 1k filter components on the VC10X and VC5X pins were wrong. I've corrected them. 

Moreover, I want to change the cell connection for BQ76940 following the recomendations of table 26 of bq76940.pdf datasheet. So, I've changed prematurelly AFE Cell Map in Data Memory according to the future change. Contsequently, after writting it to data memory I've lost the SMBus communication. I suppose that the device is in permanent fail. Is there any way to come back to previous configuration? As I'm not able to communicate, also I cannot program a new software.

Regarding, the log files. After these HW changes I will repeate the 6 log files following your advices. 

Thanks!

Hi Marco,

When the AFE Cell Map is programmed incorrectly, it can be challenging to recover the device. Some of the cells configured will be at 0V which will trigger a voltage based Shutdown. You need to wake the device again with a rising edge on the TS1 pin, but then quickly change the AFE Cell Map register before it shuts down again.

Regards,

Matt

Hi Matt,

I've repeated all 6 log files high/low temperature + high/low rate with the proper RC filter in VC10X and VC5X + the recommended 14 cell configuration of table 26 of bq76940 datasheet. Moreover, I've relaxed the protections in these 6 log files, setting for example UV=2,7V or OTD=65ºC, and I've calibrated External Average Cell Voltage as you recommended.

The reported parameters show a bigger deviation results, with the next note: "Accuracy Error: Deviation is so high that it is most likely due to anomaly in the data. Please check that data files have recomended format, units and test schedule".

I've checked all 6 data files, and I don't see any anomaly in the data. 

Could you give any idea about the reason of this deviation?

Furthermore, I've one question: If I enable EDV_EXT_CELL = 1, the calculated EDV0,1,2 by CEDV algorithm will be based only on the External Average Cell Voltage?

In other words, if the External Average Cell Voltage is around 3,5V (which could means 7% of battery) but the lowest cell voltage is near of UV=3V. How it does affect to RSOC calculation? Would I see a jump from 7% to 0%? In this case, it seems better approach using the lowest cell voltage (not EDV_EXT_CELL=1).

For example, from the 6 log files that I've collected I've seen that cell7 reaches to 3V when the ExtAvgCellVolt=3,3V. It seems that cell7 has less capacity than others.. but it can occurs obviosusly because production process or aging. I've also checked the cell 7 balance during the charging process, and it's totally ok (maximum deviation of 20-30mV respect to the others).

Enclosed you can find the 6 log files and the reported parameters. 

Package_Original6LogFiles.zip

1351.GPCPackaged-report.zip

Hi Marco,

Can you send the zip file that you submitted to the GPCCEDV tool? I don't see anything obviously wrong in the 6 log files, so I want to check that the files submitted do not have any errors.

Thanks,

Matt

Hi Matt,

Here you are the requested zip file submitted.

Thanks,

Marco1513.GPCPackaged.zip

Hi Yevgen,

Thank you for your response.

I've checked your reported file and I've seen that the parameter value EDVR1=78467 is out of range. The max value acceptable is 65535. Are these parameters still valid? 

Anyway, I've run a test with these parameters setting EDVR1=65535. During the 1rst discharge there's a RSOC jump from 12% to 7% (calculated EDV2=3676mV). This EDV2 point is above the "knee" of the discharge curve and it affects to the new calculation of FCC which becomes updated to 1,96Ah. The nominal values of these 14 cells that I'm using are 3,7V and 2,1Ah.  Later, the calculated EDV1=3653mV and EDV0=3598mV. So, the batteries remains at 0% too much time until UV occurs at 3V.

Questions:

1. After introducing the parameters, adjusting "Dod at EDV2" and executing a reset. Is it required a complete cycle from "fully charged" to "fully discharged" to update FCC and obtain in the next discharges a better RSOC% calculation? Is it mandatory for a good RSOC%? I'm wondering if this process should be added in the future production process to send batteries with good RSOC% estimation.

2. How I could improve the RSOC% results explained before? 

Enclosed you can find data graph of the discharge and charge process.

Thanks,

Marco.

Marco,

you are correct that the value shoudl be limited to 2^16-1, this normally happens naturally but this battery is has unusuall high impedance.
Anyway, I was able to re-fit the values with limiting the max, and get a good fit. Try using attached parameters.

To you other question - CEDV only learns at EDV2 threshold, so it is expected to have a jump at first discharge cycle, or if temperature or rate conditions have

changed. Some customers to implement learning cycles in production to learn FCC to reduce initial jump, but as I mentioned, change of temperature conditions will change a jump as well, so learning is only justified if yo also like to use learned FCC for some quality  control purposes. 
Unfortunately it is not normal behavior for CEDV, and you would have to go to an IT gauge to make adjustment of FCC happen earlier.

Regards,

Yevgen

GPC_report2.zip

Hi Yevgen,

Thanks for your response.

I've tested the new values and they are quite acceptable. But I've seen that the calculated EDV0 = 2943mV which is lower than UV = 3000mV. Is there any problem if EDV0 < UV ??