BQ25601D: BQ27Z561 and BQ25601 : BQ25601 charger terminates charging when battery percentage at 98%

Hello Shivani,

I need some more information in order to debug this. What was your termination current setting in both cases? Can you grab a register dump from each charger when this is happening? Did the device terminate? Can you provide a schematic?

Regards,

Mike Emanuel

Hello Michael,

Thank you for your response.

Our termination current is 180mA in both the cases. 

Below is the snippet of Charger IC register dump when D+/D- is open/floated. Please note I took this snippet before starting the charging, so it shows CHRG_STAT = 00.

Below is the snippet of Charger IC register dump when D+/D- is connected to 1.8V 10k pull up.

Please find the below Charger IC (bq25601D) and Fuel gauge (bq27z561) schematic snippet.

Please find below image of two D+/D- connections scenarios, one is D+/D- floating and 2nd is D+/D- connected to pull up.

I have taken other observation also which is that, if I am charging the battery from fully drained/discharged to full charge with 2A current, then this time fuel gauge is showing full charge at around 52-53%. (D+/D- connected to 1.8V 10k pull up).

Previously I had taken reading with battery less discharged (voltage around 3.9 v) not fully discharged in that case it was showing full charged at 98% as I mentioned earlier.

Can you please provide your inputs?

Let me know if you require more information.

Regards,

Shivani

Hello Michael,

Please find my answers inline as below:

-> What input current limit configuration is your goal?

Ans. Our input current limit configuration requirement is 2A, and Charging current requirement is 2A.

-> If you just short D+ D- together you will get DCP with input current limit starting out with 2.4 A. Why pull-up with 10k to 1.8V?

Ans. Because, we need 2A input current. and as per the below table, we have connected the 10k to 1.8V to get the 2A input current.

-> By the way, if you have the D+ D- lines connected to the USB device, we do not recommend altering the D+ D- connection on the BQ25601D (in other words just directly connect them).

Ans. No, D+ D- lines are not connected to the USB device. It is connected to pull 10k 1.8V pull up only.

-> As for the register dump, can you please confirm your termination current? You stated is was 180 mA, but in the registers I received it was 60 mA.

Ans. Yes, it was my mistake. We have set termination current to 60mA only.

Here our main concern is that, if I charge the battery by 1A in learning cycle procedure, then can I change my charge current (ICHG) to 2A or other than 1A in application/driver? If yes then, is there any impact on battery percentage accuracy?

Because here we have observed that, with 2A charge current, my battery voltage reaches to full charge (4.2V) voltage in less time, and at that time my battery percentage reading is not 100%.

While, this is not case with 1A charge current, as is it because we have performed learning cycle with 1A charge current? Is it the case?

Please provide your inputs. and let me know if you require more information from my side.

Regards,

Shivani

Hi Shivani,

Someone will get back to you by January 3rd. 

Regards,

Mike Emanuel

Hi Shivani,

Regarding the gauge reading 52%-53% from full charge to full discharge, is it possible to receive the .gg file of the gauge along with the log file of this occurring? This will allow us to look further into this issue.

Regards,

Anthony Baldino

Hello Anthony,

Sure, I am attaching the .gg files and log file taken during learning cycle.

Regards,

Shivani Patel

7571.gg files.zip4747.registers_logs.log

Hi Shivani,

Thank you for sending, the learning cycle looks like it was completed correctly.

Shivani Patel said:

Here our main concern is that, if I charge the battery by 1A in learning cycle procedure, then can I change my charge current (ICHG) to 2A or other than 1A in application/driver? If yes then, is there any impact on battery percentage accuracy?

Because here we have observed that, with 2A charge current, my battery voltage reaches to full charge (4.2V) voltage in less time, and at that time my battery percentage reading is not 100%.

While, this is not case with 1A charge current, as is it because we have performed learning cycle with 1A charge current? Is it the case?

Regarding this statement above, there should be no impact on the battery percentage accuracy if the charge current is increased from 1A to 2A in this scenario. When using a higher charge current, there could be a greater drop in voltage directly after charge is stopped, however the voltage should increase back during relax.

Shivani Patel said:

I have taken other observation also which is that, if I am charging the battery from fully drained/discharged to full charge with 2A current, then this time fuel gauge is showing full charge at around 52-53%. (D+/D- connected to 1.8V 10k pull up).

Previously I had taken reading with battery less discharged (voltage around 3.9 v) not fully discharged in that case it was showing full charged at 98% as I mentioned earlier.

If possible, can we receive the .gg and log of this situation above occurring? This will allow us to see what is occurring within the gauge.

Regards,

Anthony Baldino

Hello Anthony,

Thanks for the response.

As you asked,

If possible, can we receive the .gg and log of this situation above occurring? This will allow us to see what is occurring within the gauge.

Let me clear out here that, we have performed the learning cycle with 1A charge current during the charge stage as per the Section 3.2.3 Charge Battery to Full in Achieving The Successful Learning Cycle document and I already shared the generated .gg files and log file earlier.

Now, after successfully completing the learning cycle with 1A charge current, the generated golden image we have flashed into the board.

After this now we are charging the battery with 2A charge current in the application not in the learning cycle, so for 2A charge current there is no .gg file.

So, the observation is fuel gauge reading is differed with 2A charge current in application because golden image is generated with 1A charge current in learning cycle.

I hope I have cleared out my concern. Let me know if you need more clarity on this.

Looking forward to hear from your side.

Regards,

Shivani Patel

Hi Shivani,

Sorry if my question was unclear earlier. I understand that the previously sent .gg and log file are from when the 1A charge current was used during the learning cycle. I am looking for a log and .gg file of when the 2A charge current is being used in application so we can look into the measurements taken and what registers are being affected that could be causing the changes in the fuel gauge readings when 2A is being applied.

Regards,

Anthony Baldino

Hello Anthony,

Actually 2A current, we are using as a charge current in our BU logic. We have not performed the learning cycle with 2A current. That is why we don't have a log and .gg file for 2A charge current.

We have performed the learning cycle with 1A charge current only. And later as per our usecase requirement we have changed the charge current to 2A in BU logic.

Do you want me to perform the learning cycle with 2A charge current? Is it required so? 

Let me know if you need more information from my side.

Regards,

Shivani

Hi Shivani,

While the 2A charge cycle is occurring, is the gauge still connected to bqStudio?

There is no need to complete a learning cycle for the 2A charging. On bqStudio, you can select "Start Log" while the 2A charging cycle is occurring so the values will be accounted while it is occurring. This will allow us to look into the different registers and measurements. 

Regarding the .gg file, if there are no changes being made to the data flash parameters before the 2A charge cycle, I can use the .gg from the 1A learning cycle.

Regards,

Anthony Baldino

Hello Anthony,

Thanks for the response.

No, gauge is not connected to bqstudio when we are charging with 2A current. But I can generate and provide you the log file for 2A charging. Kindly give me one week time to collect the logs for 2A charging current. I will get back to you once I collect the log.

As you said,

"Regarding the .gg file, if there are no changes being made to the data flash parameters before the 2A charge cycle, I can use the .gg from the 1A learning cycle."

Yes, we are not changing the data flash parameters before the 2A  charge cycle, as we are using golden image (which contains data flash parameter) generated with 1A current. So, right you can refer the .gg from the 1A learning cycle.

Regards,

Shivani Patel

Hi Shivani,

Understood, thank you for doing that.

When received, we will use the already sent 1A learning cycle as the reference .gg file for this situation.

Regards,

Anthony Baldino

Hello Anthony,

Thanks for your consideration.

I have collected the logs for 2A charge current and attaching the same here with.

Let me know if you need anything from my side.

Regards,

Shivani Patel

2A_charge_current_register_log.zip

Hi Shivani,

Understood, thank you for sending.

Regarding the 52% to 53% SOC from full discharge to full charge issue, can you please tell me more about when this is occurring? Based on the .log file sent below with the 2A charging, the gauge is reading a 100% SOC when the voltage reaches 4.24V.

Is the 52% SOC being seen from the bqStudio registers?

Regards,

Anthony Baldino

Hello Anthony,

Thank you for your response.

So, after collecting the logs of 2A charge current in bqstudio, we have again collected the logs on our board. And this time fuel gauge is giving the 100% at 4.24V full charge.

Basically, we are reading the "0x2C/2D RelativeStateOfCharge()—RSOC" register only on of fuel gauge our board.

I am attaching the logs for reading full charge at 52%.

In logs, capacity value is the register value of  "0x2C/2D RelativeStateOfCharge()—RSOC",

current_cat value is register value of "0x0C/0D Current()",

volt_cat value is register value of "0x08/09 Voltage()".

So, what could be the reason of fuel gauge reading 52% at full charge (4.24V)?

Could you please provide your input on this?

Regards,

Shivani Patel

battery_percentage_show_at_52.zip

Hi Shivani,

Looking at the data sent, this is an interesting issue due to the measurements holding the same shape as the bqStudio log, just with different values for RSOC. Is it possible that there could be some scaling for RSOC that is occurring in the code that could be bringing this value down?

Also, is it possible to receive this log with the Remaining Capacity (0x10/0x11) and Full Charge Capacity (0x12/0x13)? These are the two main values used for the RSOC calculation and could give insight to how this situation is occurring.

Regards,

Anthony Baldino