BQ27220: About Auto Calibration

Hello Koji, 

Can you please send over a bqStudio log file with this behavior and the gg file for this? It is strange that you are discharging, but the remaining capacity is increasing. It should be the other way around where the gauge is decreasing and the remaining capacity is also decreasing. 

Regards, 

Jonny. 

211026.gg.csv

Hello Jonny,
Unfortunately there is no Bqstudio log file.
gg file will be attached.
As a background, when we previously communicated with Japan TI, we received a reply that this phenomenon was caused by offset drift.
At that time, I was also told that resetting the product was a solution, but that solution made the product difficult to use.
I am asking if there is any way to fundamentally prevent the discrepancy from occurring.

Hello Koji, 

In order to fully be able to debug this, I will need to have a log file with the described behavior. One possible cause here is that the gauge is not configured to read a discharge current less than 1mA. Since the discharge current here is only 100uA, this could potentially be what is causing this behavior. In order to calibrate the gauge to read currents below 1mA, you can refer to this document on Enhanced Resolution Gauging for Low Current Applications Using Scaling. 

Regards, 

Jonny. 

Hello Jonny

We are considering whether there is a way to obtain logs on the board where the phenomenon occurs. I will contact you again when I can get the log.

Hello,

Jonny is out of office today. Please expect a delayed response.

Regards,

Anthony Baldino

Hello Koji, 

Please let me know when you have a log file for this. 

Regards, 

Jonny. 

Hello Jonny

It's late, but I was able to get the data and will send it to you. 
Files with the characters (Default) are those for which register settings have not been made here.
 (setting) is the register setting.
 Both data are obtained from the same product PCB, and it has been confirmed that remcap increases only with (setting). 
Please let me know which settings are causing the problem.

PCB86(setting).xlsxPCB86(setting).gg.csvPCB86(Default).gg.csvPCB86(Defallt).xlsx

Hello Koji, 

Have you been able to look at the Enhanced Resolution Gauging for Low Current Applications Using Scaling document? It looks like the gauge isn't able to report the current, but that there is possibly some slight charge current < 1mA that is causing the gauge to increase remcap. 

Regards, 

Jonny. 

Hello Jonny,
I saw Enhanced Resolution Gauging for Low Current Applications Using Scaling. However, when the product is in operation, a current of about 1A may flow, and although the sense resistor can be increased to 80mΩ, the resolution will still be 125uA, and it will be impossible to detect a current of about 50uA when the power is OFF. I don't think it's possible. I'm currently using 10mΩ, so if you have a good sense resistor value, please let me know.
Also, if the remcap decreases or does not change when the current is below the resolution and cannot be detected, there would be no problem, but the problem is that it increases with the parameters we are using. I'm not looking for accurate detection, so is it possible to prevent the remcap from increasing?

Hello Jonny,

It is an additional question. (setting) writes 0xFFF0 to 0x9180 (CC Offset), but it is 0 in the gg file. However, the Coulomb Count of PCB86(setting).xlsx is 8, so I think writing 0xFFF0 may have had an effect. Will writing to 0x9180 (CC Offset) affect the bqstudio log file output?

Hey Koji, 

Can you send me a copy of your schematic to review the sense resistor connections? 

Regards, 

Jonny. 

Hello Jonny,

I will send you schematic near the sense resistor.

CN_BAT+ and CN_BAT- are the battery terminals. VBUS is the USB 5V power supply.

Hello Koji, 

Thanks for providing this, I do not see any obvious issues here with the sense resistor. Upon looking further, I have found an E2E post that goes over a similar behavior of incorrect remaining capacity, please take a look at this E2E post and ensure you have done the things mentioned here. 

Regards, 

Jonny. 

Hello Jonny,

Thank you for introducing E2E post. It was helpful.
 As for configuring EVD0-2 correctly, I will try doing it in the future when I get stuck. 
After investigating, we found that when using bqstudio and EV2400, the remcap increase did not occur even when the CEDV Profile was set on our PCB.
 The steps are below.
1: Sending Unseal command
2: Sending Unseal_Full_Access command
3: Import GG file(PCB86(setting).gg.csv)
4: Write with “Write All”
By executing these, the values ​​of "CC offset", "CC Cal Temp", "CC Gain", and "CC Delta" changed.
The gg file at that time is "PCB86_240603(CalibrationCurrentChange).gg.csv".
Could you please tell me what is the reason why these four parameters change when using BQstduio? 
Is this Auto Calibration? 
I would also like to know if these four parameters are parameters that can be changed.

PCB86_240603(CalibrationCurrentChange).gg.csv

Hello Jonny,

I am a colleague of Koji Yanagida. I am asking a question on behalf of Kohji.

1: Send the Unseal command

2: Send the Unseal_Full_Access command

3: Import the GG file (PCB86(setting).gg.csv)

4: Write with "Write All"

Will calibration be performed if I do the above?

When setting a CEDV profile in the PCB, do I also need to set the parameters that were changed by calibration?

Regards,

Homare Ehara

Hello Homare, 

No, this alone will not calibrate the gauge. Please read the sections in the BQ27220 TRM to find when calibration occurs. 

I am not sure what you are asking for your second question, is this for production? 

Regards, 

Jonny. 

Hello Jonny,

What I am asking for my second question is for production.

Regards,

Homare.

Hello Jonny,

Could you please explain "CC Cal Temp" as well?

Regards,

Homare.

Jonny,

Homare-san read the RTM, and has some questions about 4.9.1.1 CC Gain. Please provide detailed and specific explanations for them.
Q1: What is the “mAh capacity scale factor”?  How is it actually used? Please elaborate.
Q2: What is the calibration routines exactly? Please show the exact and specific routine example. And please explain exactly when/how it should be used. Should it be done every device at factory before shipping products?

Best regards,

K.Hirano