BQ27411-G1: Difference in current measured in fuel gauge and multimeter.

Hi Anthony

Thanks for the reply. 

Our fuel gauge is populated in our custom PCB, which has its own controller to communicate with the fuel gauge , so is there any option to calibrate the fuel gauge other than bqstudio and evk.

Hi Anthony,

I attempted to make the changes, but there was no effect on the current measurement. Are there specific procedures or steps I should follow when configuring these registers ? Can we configure these registers like any other registers mentioned in the technical reference. ?

Hi Anthony,

We have gone through this document, in this before writing the offset and gain they are entering into  calibration mode using a command (ENTER_CAL_MAC). But in BQ27411 - G1 IC they are not mentioning anything about this enter calibration mode command.

Hi Aaron,

I believe that you can still enter calibration mode for the bq27411 by using the CALMODE bit found in the Control_Status register below:

Regards,

Anthony Baldino

Hi Anthony,

Thanks for the reply, I believe the above mentioned register is read-only. 

Hi Aaron,

Can you please try changing the calibration registers using this process below:

If this does not work, please let me know.

Regards,

Anthony Baldino

Hi Anthony,

We tried it several times. But there is no change.

After referencing the document you provided, we implemented commands and read those registers mentioned in that document, even though they were not detailed in the BQ27411-G1 technical reference. We noticed that the gauge entered calibration mode when we utilized the "enter calibration mode" command detailed in that document. Is this method considered a recommended approach, and can we expect these commands and registers to be compatible with the BQ27411 IC as well?

https://www.ti.com/lit/an/slua640b/slua640b.pdf

Thanks and regards

Aaron Pulikkottil

Hi Aaron,

When you say the gauge is entering calibration mode when those commands are inputted, does that mean the CALMODE bit is returning true when read?

If so, I believe it would be a valid approach to try and input the commands for the Board Offset to see if that solves the issue.

Please let me know if that works.

Regards,

Anthony Baldino

Hi Anthony,

These are the steps we followed for the fuel gauge.

Calibrating the Fuel gauge without evaluation kit

We are currently facing issues related to measuring the current in a BQ27411-G1 fuel gauge with the following configurations:

- Design Capacity: 1800

- Design Energy: 3.9 * 1800

- Terminate Voltage: 3000mV

- Taper rate: 83

- Discharging Threshold: 10

- Opconfig: 0X25F8

- Opconfig_B: 0X0F

- LOAD_MODE: 0X00 (constant current mode)

- Qmax: 16384U

- SLEEP_CURRENT: 50

Initially, without any calibration, we noticed that the CCA bit in the control status register was set nearly 3 minutes after initialization. However, we did not observe any changes in the current. Subsequently, we followed the calibration process described below:

Calibration Method:

We implemented the Host System Calibration Method as outlined in the document for board offset calibration. We used the provided addresses and commands, even though this procedure was not extensively detailed in the BQ27411-G1 Technical Reference Manual.

When we enabled the calibration using Subcommands 0x002D and 0x0081, the CAL_MODE bit was set.

Board Offset Calibration:

For board offset calibration, we utilized Subcommands 0x0009 as provided in the document, resulting in the BCA bit being set.

CC Offset Calibration:

To address CC offset calibration, we applied Subcommands 0x000A from the document, which led to the setting of the CCA bit.

Current Calibration:

This included adjusting CC gain and CC delta

Modifying the CC delta had an impact on the remaining capacity and state of charge, occasionally resulting in values of either zero or unpredictable variations.

We are actively seeking to resolve the issues with current measurement in the BQ27411-G1 fuel gauge through these calibration steps.

Hi Aaron,

I do not believe the CC Calibration values are supposed to be changed, only the Board Offset. Seen in the document below, the CC Offset is an automatic calibration that occurs when the battery is in sleep mode. Also, the CC Delta is supposed to be a fixed value based on CC Gain.

Based on this, is there no change in the results if only the Board Offset Calibration is changed? 

Hi Anthony,

When we changed the CC gain, we were able to see changes in the average current . We followed current calibration method detailed in the document .

Is there any way to scale the SOC and remaining capacity ?

Thanks and Regards

Aaron Pulikkottil

Hi Aaron,

Can you please elaborate on what you mean by scale?

Regards,

Anthony Baldino

Hi Anthony,

Sorry for the confusion.

Our fuel gauge is BQ27411-G1C. It is used for battery of maximum 4.35V , but the battery we are using is maximum voltage of 4.2V. When we charge the battery to maximum voltage of 4.2V we are not achieving 100% of SOC or full remaining capacity. Is there any way that we can adjust this, at least nearer to 100% ?

Thanks and Regards

Aaron Pulikkottil

Hi Aaron,

Thank you for the clarification. Is it possible for you to send the .gg file of the gauge from bqStudio so we can look at the current settings?

Regards,

Anthony Baldino