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BQ27427EVM: BqStudio does not detect the end of charge in the learning cycle

João Rego
Intellectual 296 points
Part Number: BQ27427EVM
Other Parts Discussed in Thread: BQ25170EVM, BQ27427, GPCCHEM, BQSTUDIO

Hello,

I am doing a learning cycle to a Li-ion battery with the aid of the BQ27427EVM. This battery has a capacity of 250mAh, a nominal voltage of 3.7V and a charge voltage of 4.2V. However, when I am doing the learning cycle, I can't pass from the charge state to the relaxed one. As you can see in the image below, the learning cycle stays in the charge state even with a battery voltage above 4.2V. Should I do anything else to continue the learning cycle?

Before starting the learning cycle, I programmed the correct chemistry ID (1202 in this case). To charge the battery, I am using the BQ25170EVM with a 4.2V configuration (R5) and a maximum current of 100mA.

Thank you in advance,

João Rego

  • 0
    TI__Mastermind 25261 points

    Hello, 

    I recommend referring to this document on achieving the successful learning cycle to ensure you have all of your parameters configured correctly. Additionally, how did you match the chemID? 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 296 points

    Hello,

    As the BQ27427 Technical Reference Manual says "the BQ27427 cannot be programmed with specific battery chemistry profiles. Three pre-defined chemistry profiles (shown below) are available in the device memory. For many battery types and applications, these profiles are sufficient matches from a gauging perspective". So, I selected the 1202 chemistry ID, which has a charge voltage of 4.2V, equal to the battery chosen.

    Regarding the document about achieving a successful learning cycle, I noticed that I hadn't programmed the data flash parameters (design capacity, design voltage, charge term taper current, dsg and chg current threshold, quit current and term voltage). However, I can't find the design voltage and the charge term taper current in the data memory section. I know that the design voltage should be in the gas gauging subsection and the charge term taper current in the advanced charge algorithm subsection (although I don't have this last option).

    Best regards,

    João Rego

  • 0 in reply to João Rego
    TI__Mastermind 25261 points

    Hello João, 

    The reason I am asking about the chemID match is because sometimes just because the charging voltage for the chemID is the same as the charging voltage of your cell, does not necessarily imply that the match is the best. In most cases having the same charging voltage as the chemID provides an adequate match though. 

    With this being said, I do not believe that the chemID is the issue based on your comments above. You must configure the parameters listed in the Achieving the Successful Learning Cycle document at a minimum in order to successfully complete the learning cycle. On this gauge, there is no charge term taper current parameter here, instead, you will want to configure the Taper Rate parameter. Additionally, you do not need to program a "Design Voltage" parameter.

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 296 points

    Hello Jonny,

    After configuring the parameters listed in the document, the learning cycle passed from the charging state to the relaxed one. Now, I just need to complete a full learning cycle. Due to its longer time, I will go with the automated mode. I just need to buy two relays.

    Thank you for your help. If further help arises, I will let you know.

    Best regards,

    João Rego

  • 0 in reply to João Rego
    TI__Mastermind 25261 points

    Hello João Rego, 

    This sounds good! Let me know if you have more questions. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 296 points

    Hello Jonny,

    I came across another issue. After the initial battery discharge, the gauge gives the [RUP_DIS / RDIS: Not Clear] error after some time in the relaxed mode. Do you know why I have this error? To mention that in previous learning cycles, I was able to pass from the relax state to the charge state and finish the charging as well.

    Best regards,

    João Rego

  • 0 in reply to João Rego
    TI__Mastermind 25261 points

    Hello João Rego, 

    In the past, I have seen this error getting caused by an incorrect chemID. Did you end up using the GPCCHEM tool? 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 296 points

    Hello Jonny,

    I didn't use it because I thought that the battery charging voltage of 4.2V was the chemistry ID to be selected. From what I have read this is a wrong assumption.

    I have some questions about the GPCCHEM tool:

    • Do I need to log a file of a charge / relaxation / discharge / relaxation or just relaxation / discharge / relaxation? The Simple Guide to Chemical ID Selection Tool (GPC) mentions the first one, while the video on the GPCCHEM page mentions the second.
    • Do I need to charge with the taper current? This would take some time to charge.
    • Lastly, is there any way to do this autonomously inside bqStudio? From my calculations, this process would take approximately 27 hours (charging and discharging with a C/10 rate, 2 hours from relaxing after charging and 5 hours from relaxing after discharging).

    Best regards,

    João Rego

  • 0 in reply to João Rego
    TI__Mastermind 25261 points

    Hello João Rego, 

    For the log file, the initial charging period is not required for the tool, although the charging must be done very shortly before the relaxation period. The Relaxation data is required before and after the discharge. What you can do is collect the charge, relax, discharge, relax data, then just crop out the charge portion of the log file if you do not wish to include the . Your data should look something like this: 

    You should charge using CV/CC and using the taper current specified by the cell maker.

    BQStudio does not support this feature. The relax is important to ensure accurate OCV measurements are taken. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 296 points

    Hello Jonny,

    I have received the gauging parameter calculator report and it says that the best chemical ID is 270. Since I am using the BQ27427 I cannot program any chemistry ID from your database. However, the report mention some default IDs that I could use. From these IDs, the report mentions the 3142 (4.4V charging voltage) which is available in BQ27427.

    I will redo the learning cycle with this ID and I will let you know about the results.

    Thanks.

    Best regards,

    João Rego

  • 0 in reply to João Rego
    TI__Mastermind 25261 points

    Hello João Rego, 

    Thanks for the update here. What was the DoD % Error of the recommended chemID for the BQ27427? 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 296 points

    Hello Jonny,

    The error is 22,93%. Shouldn't this percentage be below 3%? 

    Before your question, I hadn't looked at this parameter. Also, the other chemIDs have an error of 23% and 24% which are very close to the recommended chemID.

    Best regards,

    João Rego

  • 0 in reply to João Rego
    TI__Mastermind 25261 points

    Hello João Rego, 

    Yes, a DoD % Error of 22% is very high. The fact that your best match is in the 20% range leads me to believe that there could be an error with the data submitted for the GPCCHEM tool. Can you please provide me with the data you submitted to the tool as well as the GPCCHEM report you received? 

    Thanks, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 296 points

    Hello Jonny,

    I can provide you with the data as well as the report. However, I am aware that the data submitted is not correct since I didn't discharge with a CC. I was with lack of time so I had to increase the discharge current to submit the data before the end of the day. As you know, this process is not ideal since it takes almost 24 hours.

    Thanks.

    Best regards,

    João Rego

    0652.config-report.zip

    4101.config.zip

  • 0 in reply to João Rego
    TI__Mastermind 25261 points

    Hello João Rego, 

    Thank you for including this. It seems like this inaccurate match was likely due to the data you have submitted to the tool. Please recollect and resubmit the data to the GPCCHEM tool using a discharge of C/10. 

    Regards, 

    Jonny.