BQ27742EVM: Cell capacity reading

Hi,

Thanks a lot for your help. I have been trying to follow the steps but I couldn't make out a picture. Can you please provide a little guide on how to determine the chem ID of a cell and how to perform a learning cycle? Is there any note or manual that I can refer to? I am using Battery Management Studio v1.3.54 for evaluating the bq27742EVM. Should I use a different software?

Hi,

The Battery Management Studio v1.3.54 contains the GPCPackager tool for devices like  BQ4050, but I am not able to find it for BQ27742-G1. How do I create the zip file (for uploading in the web tool as advised in the link) for determination of chemistry ID, using Battery Management Studio v1.3.54? Or, is the tool not available for BQ27742-G1, and do I have to create it manually then?

Thanks for helping.

I was trying to do a learning cycle using the tool in Battery Management Studio v1.3.54. It was in the relaxing cycle, but somehow it lost connection and reported device acknowledgement error. But when I reconnected, the fuel gauge was reading a discharge current of -24635 mA, displayed in the meter, even when no load was connected. I checked for short circuits, but there was none. I also measued the voltage drop across the on_board 5 milliohm sense resistor, but it reads 0 mV, which means no current is flowing through it. Now, the gauge is not showing correct values of current, SOC but measuring the cell voltage correctly. Please help.

Thank you.

• www.ti.com.cn/.../slva725.pdf
• Hi，you can follow the instructions above to make the zip file manually. 
• Create each file according to the PDF file and then compress to a zip file.

Thanks for helping.

I was trying to do a learning cycle using the tool in Battery Management Studio v1.3.54. It was in the relaxing cycle, but somehow it lost connection and reported device acknowledgement error. But when I reconnected, the fuel gauge was reading a discharge current of -24635 mA, displayed in the meter, even when no load was connected. I checked for short circuits, but there was none. I also measued the voltage drop across the on_board 5 milliohm sense resistor, but it reads 0 mV, which means no current is flowing through it. Now, the gauge is not showing correct values of current, SOC but measuring the cell voltage correctly. Please help.

Thank you.

Hello,

Thanks for responding quickly. I have tried uninstalling and then reinstalling the software (Battery Management Studio v1.3.54). I have disconnected and then reconnected the hardware equipments. But it is of no use, the software is displaying random and unpredictable values of current like 6220 mA, -22674 mA, -600 mA, 866mA, 124mA etc. at random times and accordingly increasing or decreasing the displayed value of SOC %. But actually, as no load or charger is connected, neither the SOC% can change, nor the current flowing into or out of the battery. Also, I don't think there is any issue with the internal ADC of the BQ27742-G1, as it is correctly displaying the battery voltage. Please help at addressing the problem.

Also the voltage at CHG and DSG pins is measured to be 2.99V and 6.1 V respectively (Battery Voltage is at 3.2V), (earlier it was measured 3.0, 2.6 V respectively) but I cannot charge or discharge without putting the FET bypass jumper on. Maybe some issue with the FET.

As hardware equipments, I have used EV2400 as an I2C interface, BQ25890EVM evaluation charger board with BQ25890H as the charger, the BQ27742EVM evaluation gauge board with BQ27742-G1 as the fuel gauge, two SAMSUMG INR18650-25R battery cells connected parallely as a single pack, and a standard 5 ohm, 10 Amp rheostat as a load (at 1 Amp setting).

Please note that there might be a possibility of an accidental event of short circuit, while the gauge was in the relaxation cycle of a learning process, and was left unattended. However, no load or charger was connected. The only power source was the battery itself.

Thanks for helping.

Thanks a lot Phil.

Yes, the FET was damaged already. I dismounted it. Now, everything is working normally. I was not sure about how the FET could be interfering with the SRN, SRP pins as they were all working normally, including the filtering network. Also,the 5 milli ohm sense resistor is working fine. I bypassed the FET through the jumper, yet the gauge was not able to display live updates of current.

Anyways, thanks a lot!

  Ok, the voltage between SRN and SRP is the current measuring input, if current reading is not normal, usually these 2 pins and related connections have issue. Please let's know if you need any other helps.

Thanks!

Phil

Hello,

I am trying to send command to the BQ27742-G1 gauge and read using the advanced communication tool available in Battery Management Studio v1.3.54.  I only know the respective commands like 0x0000 for control status register but I don't know the register address. May I know in which address I should sent the command and from which register we can read the value or data?

Thanks for helping.

Thanks a lot Onyx,

That was immensely helpful.