BQ27426: Reasons for increase in RM value

Hello,

1、SMOOTH_EN默认是开启的，还是不明白，为什么还要周期发送SMOOTH_SYNC？SMOOTH_SYNC主要是什么作用？

1, SMOOTH_EN is on by default, still don't understand, why do we need to send SMOOTH_SYNC periodically, what is the main role of SMOOTH_SYNC?

Jose Couso said:

1- In the event where the filtered values differ a lot from unfiltered values, it is recommended to send the SMOOTH_SYNC command periodically. This is often seen when the coulomb counter has accumulated a lot of charge error (undesired charge). 

2、我做了验证，使用仪器监控电池RELAX期间的电流，电池只有自损耗，没有反向漏电流，仪器的精度为uA。所以没有累积负电流。

2, I did the verification, using the instrument to monitor the current during the battery RELAX, the battery has only self-loss, no reverse leakage current, and the accuracy of the instrument is uA.So there is no cumulative negative current.

Jose Couso said:

3- If positive current is sensed, it will act as charged current. So when the gauge takes an OCV measurement it will update RM. If accumulated current is negative, it will be the opposite.

Hello jose,

Thank you for your reply.

Two more queries:

1、每次进行OCV测量时，RM、FCC的真实值都会重置吗？

2、Guage执行OCV测量的前提条件是什么？间隔周期是多久？

1, As soon as the OCV measurement is performed, the true values of RM and FCC are reset?

2, What are the prerequisites for Guage to perform OCV measurements? What is the interval period?

Hello，

Need help:

Using a degraded battery with a full charge capacity of only 300mAh, inserted into the device, the Fcc obtained is 853mAh, which is a gross discrepancy from the actual capacity.

1, According to the application manual, TRUE FCC will update when the temperature changes more than 5℃ or exit from Relax mode or rest for 5 hours. However, TRUE FCC is not updated under these scenarios in real test.

2、Using a degraded battery and installing it directly on the TI Demo board, what operations need to be performed so that Filtered FCC will be updated to match the degraded battery?

3、If the battery is used in a scenario where it can't be fully charged or fully discharged (SOC=30% to stop charging, SOC=8% to stop discharging), will the Filtered FCC be updated during use?

使用满充容量只有300mAh的劣化电池，插入到设备中，获取到的Fcc为853mAh，与实际容量的严重不符。

1、根据应用手册，TRUE FCC会在温度变化超过5℃或者从Relax mode退出或者静置5小时都会更新。但实测这些场景下，TRUE FCC都没有更新，请问是什么原因？

2、使用劣化电池，直接安装到TI Demo板上，需要执行哪些操作，Filtered FCC会更新到与劣化电池匹配？ 

3、如果电池使用的场景，不能满充，也不能满放(SOC=30%停止充电，SOC=8%停止放电)，在使用过程中，Filtered FCC会更新吗？

Hello Wang,

1- The gauge will run simulations at the following conditions

• Grid points where resistance table is updated
• Temp change
• Start of charge
• Start of discharge,
• Every hour in relax
• Valid charge termination
• OCV Reading

2- If using an older battery cell, the user must write appropriate data flash parameters. You will probably have to do a sanity cycle to allow the gauge to learn about the degraded cell.

3- Impedance Track algorithm does not need a full charge/discharge to update Qmax. It should be able to predict capacity. Make sure you are using a dynamic load select such as 1. See below


Regards,
Jose Couso

Hello jose，

1、我们实测Temp change、Start of charge、start of discharge和Relax这几个场景，都没有更新，请问是什么原因？

2、"a sanity cycle"是什么意思？我的理解是一个完整的充放电，理解对吗？这个是必须的吗？是否还有其它方法？

3、我们的配置是：Load mode=0x81，属于动态负载吗？

1、We have tested Temp change, Start of charge, start of discharge and Relax scenarios, but they are not updated.

2、What is the meaning of "a sanity cycle"? My understanding is a complete charge/discharge, is that correct? Is this a must? Is there any other way?

3, Our configuration is: Load mode=0x81, is it a dynamic load?

Hello Wang, 

1- Please share the log file and configuration file.

2- Sanity cycle = complete charge-relax-discharge-relax cycle

3- Correct, present average load is for dynamic applications where the load changes continuously. 

Regards,
Jose Couso

Hello Jose，

1, please check the attachment, the log is generated by our device, and the log format is different from TI demo.

The "Fuel_" prefix in the log represents the Filtered value obtained from FuelgaugeIC.

The prefix "bq27426 True" in the log represents the unfiltered value obtained from FuelgaugeIC.

The corresponding keyword for temperature is "Bub Ntc:"Test log.zip

Jose Couso said:

1- Please share the log file and configuration file.

2、What is the Filtered FCC update mechanism?

3、If the sanity cycle cannot be performed during use, is there any other way to make the Fcc value match the inserted degraded cell?

Jose Couso said:

2- Sanity cycle = complete charge-relax-discharge-relax cycle

Hi Wang,

It is hard to debug a log file that is not in the same format as the BQStudio logs. 

2. Please see this FAQ to understand Filtered vs True. 

3. From the gauge point of view, it needs to know the history of the cell. One solution is to save the last status of the degraded cell and upload the learned parameters such as Qmax value. If this info is not available, then a full charge-discharge cycle will need to be done. 

Regards,
Jose Couso

Hello jose，

Thanks for you reply.

In response to the scenarios where True Fcc can be updated, please help confirm if I understand correctly?

1、The seven update scenarios listed, True Fcc will update if any one of them is met.

-Temp change--> During battery Relax or charging or discharging, the amount of temperature change over a period of time (how many seconds exactly) The True FCC will be updated if the temperature changes by more than 5℃, no other additional conditions are needed.

-Start of charge-->True Fcc will be updated when the battery changes from Relax to Charge, no other additional conditions are needed.

-Start of discharge-->True Fcc will be updated when the battery changes from Relax to Discharge, no other additional conditions are needed.

-Every hour in relax-->True Fcc will be updated every hour in relax state, no need other extra conditions.

-Vaild charge temination-->True Fcc is updated when the battery is fully charged with SOC=100%, no other additional conditions are needed.

2、How to simulate the two scenarios below:

·Grid points where resistance table is updated-->？？

·OCV Reading-->??

3、Using TI studio, if the value before and after True Fcc update is the same, how can I confirm that True Fcc has been updated and is there a corresponding flag?

Jose Couso said:

1- The gauge will run simulations at the following conditions

• Grid points where resistance table is updated
• Temp change
• Start of charge
• Start of discharge,
• Every hour in relax
• Valid charge termination
• OCV Reading

Hello Wang,

1- Correct, but if it does not update, it simply means it stayed the same value. The best update to rely on is change in temperature and change in load.

2- The resistance table will update at the end of the discharge cycle. You can export the Ra before and after the discharge cycle.



VOK indicates the last OCV measurements qualified for a Qmax update. See if this bit toggles. 

3- No corresponding flag, but in the log file, there should be a True reported value that you could plot and see how it changes.


Regards,
Jose Couso

Hello Jose，

1、Temp change --> Is there a time limit for the temperature to exceed 5°C? Within what time period will a temperature change of more than 5°C be determined to satisfy the condition?

According to my understanding of the FAQ, when Smooth is enabled, SOC is calculated using Filtered Fcc, but there is no description of the Filtered FCC update condition：

2, What scenario will be synchronized to Filtered Fcc after True Fcc update?

3, What scenario will Filtered FCC update?

Regards,

wang dong

hello Jose.

Sorry still have to get back to this thread.

I still have some questions about the fcc update conditions:

1, For Discharge Cycle, my understanding is: Charge -> Full Charge (Soc=100%) -> Relax 2 hours or more -> Discharge -> Power Empty (Soc=0) -> RA table update

Is the understanding correct? As long as the Discharge Cycle is satisfied, the RA table will be updated?

Jose Couso said:

2- The resistance table will update at the end of the discharge cycle. You can export the Ra before and after the discharge cycle.

2、Do I need to set RUP_DIS to True if I want to update RA table?

3、What parameters are needed for Gauge to fully match the degraded battery, Qmax, RA table?

4、After performing a full charge, full discharge cycle, Guage's Fcc value matches the degraded battery.

If Q1 is understood correctly, then it is equivalent to matching a degraded battery after the following two conditions are met. Why don't the other conditions allow Guage to match the degraded battery?

• Grid points where resistance table is updated
• Every hour in relax

Jose Couso said:

3. From the gauge point of view, it needs to know the history of the cell. One solution is to save the last status of the degraded cell and upload the learned parameters such as Qmax value. If this info is not available, then a full charge-discharge cycle will need to be done.

Best Regards，

wang dong

Hi Wang Dong,

1- That is correct. Ra table should be updated at the end of discharge cycle.

2- When RUP_DIS is high/true it indicates that the Ra updates are disabled. 

3- Please see section 4 in the quick start guide.

4- FCC is not expecting to change much. Specially is smoothing is enabled. Please provide a BQStudio log to look in the data.

Regards,
Jose Couso

Hello Jose，

1. Inserting a degraded battery requires that the Design Capacity, Design Energy, Terminate Voltage, and Taper Rate parameters of the degraded battery be rewritten into the FuelgaugeIC.The discharge operation is then performed to update the Qmax and RA Table。

Is this understanding correct?

2. The Gauge can be matched to the battery after performing a full discharge cycle for a degraded battery. So, the above parameters, after performing full charge-full discharge, will be updated?

3、If only FILTERED FCC and Qmax are needed to have a downward change, without having to fully match the degraded battery, what conditions need to be met?

Jose Couso said:

3- Please see section 4 in the quick start guide.

4, Can you explain the reason why the FCC can't be updated?

Jose Couso said:

4- FCC is not expecting to change much. Specially is smoothing is enabled. Please provide a BQStudio log to look in the data.

5, Using TI Studio to capture the logs, please help to analyze the reason why Qmax and Fcc are not updated.
Test procedure:
Discharge for 8 minutes and let it sit for 1 hour or more. Can meet Fcc update conditions (Start of discharge and Every hour in relax)

Question 5 was also asked in another thread.

0385.TI_chg_relax_dsg_test_Fcc_1110.zip

Best Regards,

Wang Dong

Hello Jose，

Please help respond to the above question, thanks!

Also, updated the log for the BQstudio test. Tests: temperature change over 5°C, charging, discharging, and resting over 5 hours.

Please help to analyze the logs and confirm the reason why Filtered FCC and Qmax are not updated?

Best Regards,

Wang Dong

Ti_charging_discharge_Relax_Tmore than5℃.zip

Hello Wang Dong,

The gauge requires a true learning cycle (UpdateStatus = 0x03 for the bq27426) before it can gauge a significantly aged cell accurately.

Filtered FCC



Temperature is not stable



the gauge only accumulated about 70 mAh (this is only a few SOC %). The first Qmax update requires 90% passed charge.  

Also, the collected data does not look ideal. See below how data should be collected. You should be using current sources with 1% accuracy.



Regards,
Jose Couso

Hello Jose，

We validated using TI Demo board+BQstudio+deteriorated battery (with a full charge capacity of 760mAh, including 350mAh reserve capacity). Please help analyze the logs. Thank you!

Phenomenon: Filtered Fcc did not change during Relax and Discharge.

During the charging process, Filtered Fcc decreases, Filtered FCC=669mAh at the beginning of charging, and Filtered FCC=675mAh at the end of charging. Charging time ≈ 12 minutes, charging current 400mA.

TIDemo_BQstudio_log.zip have two logs in total:

Relax_ Discharge_ Relax_ Charging_ Relax. log: 570mA -->Relax for over 10 minutes -->discharge -->500mA -->Relax for over 30 minutes -->charging -->570mA -->Relax for 30 minutes

Discharge_ Relax13hr. log: 570mA ->Discharge -->500mA ->Relax 15 hours

TIDemo_BQstudio_log.zip0601.0418_New_Bat_FS_withChemID_0419.gm.zip

Hello Wang Dong,

I am not really sure what is the main issue here.

Wang Dong said:

Phenomenon: Filtered Fcc did not change during Relax and Discharge.

Filtered FCC is not expected to change often. These are filtered (smoothed) values. FCC is not expected to change much overall. It will decrease over time when the cell starts degrading. FCC increased when you charged, the gauge predicted more capacity. 

The gauge is doing good SOC estimations. No jumps in SOC.

Regards,
Jose Couso

Hello Jose,

Sorry, my description of the problem is not clear.

Based on the BQstudio logs, my question is:

1. The two logs are continuously tested. Why does FCC and Qmax not update in scenarios where DOD1 and DOD2 can be updated (Relax+discharge+Relax for more than 5 hours, "Discharge_ Relax13hr. log")?

2. Why is Filtered FCC decreasing during charging(Relax_ Discharge_ Relax_ Charging_ Relax. log)?

Wang Dong said:

During the charging process, Filtered Fcc decreases, Filtered FCC=669mAh at the beginning of charging, and Filtered FCC=675mAh at the end of charging. Charging time ≈ 12 minutes, charging current 400mA.

Best Regards,

Wang Dong

Hello Wang Dong,

1-  If it is the first Qmax update, it is required to charge the battery 90% from empty. If the first Qmax has already been learned, then it is required 37% of charge for Qmax to update. Your test reflects otherwise. See below.




Please force update status to 3, and charge the battery to full from empty. 

2- In your test, FCC increased during charge. At full charge state, the gauge predicted more usable capacity. See below. This is normal. No issues here.


Regards,
Jose Couso

Hello Jose,

Thanks for you reply,

Our device is loaded with FS files. The FS file is based on a new battery.

1. How to understand 'First Qmax update'? Does the QMAX Cell 0 value in the Fs file belong to First Qmax?

2. Must the PassedCharge for charging or discharging exceed 37% in order to update Qmax?

3. Can it be understood as: inserting an aging battery requires re performing golden learning before FuelGauge can accurately match?

Jose Couso said:

1-  If it is the first Qmax update, it is required to charge the battery 90% from empty. If the first Qmax has already been learned, then it is required 37% of charge for Qmax to update. Your test reflects otherwise. See below.

4, Your reply, is just the opposite of my question.
bqstudio log: Relax_Discharge_Relax_Charging_Relax. log

Filtered FCC is decreasing during charging, what is the reason?1030.TIDemo_BQstudio_log.zip

Wang Dong said:

2. Why is Filtered FCC decreasing during charging(Relax_ Discharge_ Relax_ Charging_ Relax. log)?

Wang Dong said:

During the charging process, Filtered Fcc decreases, Filtered FCC=669mAh at the beginning of charging, and Filtered FCC=675mAh at the end of charging. Charging time ≈ 12 minutes, charging current 400mA.

Jose Couso said:

2- In your test, FCC increased during charge. At full charge state, the gauge predicted more usable capacity. See below. This is normal. No issues here.

Hello Wang Dong,

1- No, Qmax cell 0 corresponds to the last update in Qmax for the first cell which in this case is only one cell.

Update Status = 3 indicates that a learning cycle has been done. Hence, Qmax and Ra table has been learned. This indicates the first Qmax has been updated.

2- Correct, the passed charge needs to be greater than 37% at least after the first Qmax update. 90% if Update Status is zero.

I suggest to force Update Status = 3, and charge at least 37%  

3- If you have obtained a golden image for a new cell, this will be different from the age cell. The gauge needs to know what has happened to the state of the battery, the gauge will only know this if you allow the gauge a charge to full and discharge to empty.

Aged cells indicates that internal resistance is higher. If you have the latest state of an aged cell, you can create an "aged golden image" and upload it to when using an aged cell that matches the state of the battery when you created the aged golden image. Otherwise, please allow a full charge and discharge so that the gauge learns the current state of the cell.

4- Positive current means charging. Negative discharging, and 0A means relax



Regards,
Jose Couso

Hello Jose，

Happy Thanksgiving！

1, According to TRM, Qmax Cell 0 is calculated to get Qmax. after loading the FS file, Qmax is calculated by the formula below before the value of Qmax Cell 0 is changed, is this understood correctly?

If it is correct, why is it not part of the FIRST Qmax?

Best Regards!

Wang Dong