BQ27510: BQStudio Learning cycle not following expected behavior

 hi Robert.

1. Yes it is 100% required. it's ok if your protection circuitry kicks in and turns off the fets.

2. section 2.4 in the document you mentioned about said to identify your chem id. This is a mandatory step.

3.you need to identify and program the correct chem id following the instructions outline in the app note and you need need to follow the instructions stipulated in the app note, one of which was waiting 5 hours after discharge and 2 hours after charge.

thanks

Onyx

Onyx Ahiakwo 

Thank you. Just to clarify:

2. ChemID has to be programmed correctly before the learning cycle, is this correct? If so, I use TI App note SLVA725A to determine the correct ChemID. 

3. The learning cycle does not mention the rate at which to charge. Are there limits? I'm currently charging at 1C (1300mA), which is what our application will charge at. Is this too high for a proper learning cycle? 

Regarding App Note SLVA725A, for a Li-Ion cell (Section 3.1), it states to use a charge current of C/100. This seems very unreasonable and time consuming. Is there an upper limit to the charging current we can use, especially considering the same App note says that "The initial charging portion is not required. The charging must be performed shortly before the relaxation period. Relaxation data is required before and after the discharge."

Thank you,

Rob

hi Rob

2. Yes. The app note mentions that clearly. Yes, SLVA725A is what should be used. App note mentioned this as well.

3. No. There is no limits for charging. C-rate is ok.

for chemid  identification, use c/2 or c rate for charging. That will work fine. I believe the c/100 is what is required for taper and not charging. C/20 can be used for taper in case you don't want to wait for c/100

thanks

Onyx

Onyx Ahiakwo 

I have tried the learning cycle many times with my battery and cannot seem to get the Update Status to become 01. I have followed the instructions as thoroughly as possible, using ChemID 3547 which TI sent to me. Please see my below comments / questions:

1. When I discharge my cell to empty and let it relax for 5 hours, I discharge the cell until the PCM opens ~3.0V. At this point the fuel gauge is unpowered. How does it know that 5 hours has passed? Contrary to the graph TI presents, the cell voltage does not rebound and close the PCM switch. Usually, I end up turning on the charger for a second to close the PCM, but regardless, the fuel gauge has been unpowered for 5 hours. Are you 100% sure the PCM can open and therefore power off the fuel gauge? If this occurs, do I have to re-enable the impedance track and re-reset the fuel gauge?

2. I'm charging to full with roughly C/2. I have charged until there is zero current entering the battery, and let it sit overnight. It's obvious >90% of the cell capacity has entered the cell. Yet I can never get Update Status to become 01, and Qmax to update.

3. Am I supposed to update Qmax manually before the learning cycle?

Any advice is appreciated. I have run out of ideas to get this learning cycle to work, and weeks of performing this process over and over has wasted plenty of time. 

Hi Onyx Ahiakwo,

Thank you for the assistance. I am trying the learning cycle again, without letting the PCM open.

1. At the bottom end of discharge, after the load has been removed and the battery is relaxing, my battery voltage decreases slowly, instead of leveling off. This makes it difficult to know where to cutoff the end of discharge, yet at the same time, not allow 3.0V to be reached within 5 hours. This being said, is there a way to know when the OCV(DOD) measurement has been taken in case I cannot wait 5 hours? What are the parameters that control when these OCV(DOD) measurements are taken? I don't need a fuel gauge that is accurate all the way until the PCM opens. 

2. I think your answer number 3 above is incorrect in mentioning design energy. This isn't a parameter to set that I can find.

Thanks,

Rob

Hi Onyx Ahiakwo and TI,

I have completed what is probably my 12th learning cycle attempt, following the TI instructions set forth in SLUA902, none of which have ever updated Qmax or Update Status after the charging section. These learning cycles have proven to be a complete waste of time over the past many weeks. I would like further clarification on why these learning cycles are not seeming to take. Attached is my log file from the attempt. 

1. I have programmed the ChemID (3547), design capacity (1300mAh), terminal voltage (3300mV), discharge and charge current thresholds (both 35mA), quit current threshold (25mA), and taper current (50mA).

2. With the battery fully discharged, but PCM closed (battery voltage around 3200mV) and fuel gauge powered, I enable an impedance track and a reset command. As the cell is already discharged and below the terminal voltage I don't need to discharge it more. Rather, I wait 5 hours as instructed. 

3. Charging commences and lasts for a few hours until charge current is around 30mA, at which point the charger is turned off. The FC bit gets set. I let the battery relax with the charger off overnight, yet the Qmax and Update Status are never updated. I can confirm, as shown in the log file, that the fuel gauge is always powered. Everything is done at room temperature. 

A couple questions / comments:

1. I've noticed the Transaction Log in the bottom right corner of BQStudio never shows me a result when I send commands. Every result is N/A. Is this normal?

2. The fuel gauge always becomes sealed during the learning cycle, although I never seal it myself. Is this expected?

3. Is there any way to just send the battery to TI to get this learning cycle done and receive a golden image file?

Thank you and I appreciate some assistance. Log file below:

Tue27Aug_RadioBatt_LearningCycle.log

Hello Robert,

-Your terminal voltage should be set to the minimum that your cell is rated for and not 3300. After learning is successful, you can set that to the 3300 which your system requires. However, I would not recommend using 3300 as your terminate voltage as using a high value can cause issues.

-you should not be using  a device that is sealed. A reset command will seal the gauge again.

-You must have sealed the gauge unknowingly at some point. Once the device is sealed, it can never return to a permanently unseal state. To get the gauge to be able to return to a permanently unseal state, program the default firmware. link below

-Unfortunately, we do not perform learning cycles for customers. Can you let me know why the cell voltage is reducing instead of relaxing upwards. This could be preventing the gauge from taking a proper dv/dt measurement used for calculating the qmax. You need to determine if your cells is being loaded by some components on the board.

thanks

Onyx

Hi Onyx Ahiakwo,

Attached are my log files for my most recent learning cycle attempt. After the many hour wait after the full charge, Update Status did not update to 01. Regardless, I have continued with the discharge cycle. This has all been done with a brand new (never sealed) BQ27510 EVM board.

It has now been more than a month of me attempting this learning cycle without ever getting Update Status to update to 01. We have our final firmware deliverable at the end of this week, which I'm not optimistic about meeting. Any advice is appreciated. 

Thanks,

Rob

0003.Thu5Sep_Radio.log

Thu Sep 05 15:26:45 PDT 2019

Time,LogCaption,Error Code,Error String
2019-09-05 15:26:45,CtrlStatus,772,No acknowledge from device.