BQ24610: Components Smoking?Burning when Charging Starts

Good day,

I have designed a 3 cell  BMS (3 X 18650 in series) and Charger system based on the componments and datasheets of BQ24610 (charger) and BQ77915 BMS.

I have attached some images to help solve my problem. The design is being used to develop a remote, I have therefore removed all components which extend beyond the BMS and Charging system as they are working perfectly.

I have added a disconnect switch (SW4) which disconnect power to/from the charger on the pack + side. When SW4 is switched off it also leaves the PRES pin floating on the BMS IC which turns off CHG1 & DSG1 mosfets. Thus when SW4 is switched off the battery cells are completely isolated from the charging system.

I have tested the remote system with Battery Power only, which works well and passes all tests.

I have also switched off SW4 and powered the remote system through the chargers power path and all works well.

My issue is when I turn on SW4 to connect the pack to the charger components begin to smoke.

- On my first test the thermistor ground pin coming from BQ24610 TS pin began to smoke and burnt until the charger IC stopped charging. Tests were done for shorts in this area and none were found.

- A second test was done with another thermistor and the same result was found, smoking at the ground pin of the thermistor.

- A third test was done by replacing the 10K NTC thermistor with a 10K resistor. This resulted in smoking and burning out of the mosfet "Q3" which when turned on is supposed to supply power to the coil L3 to charge the pack.

- It was also noted that when the batteries were in place and the charger was turned on, the LED on the PG would illuminate as well as the LED on the STAT1 pin. It seems normal that the PG pin LED remains on as there is power from being plugged in for charging, however STAT1 represents charging complete which is false as the batterie pack only measures 10.9V and needs to charge to 12.6V. I would expect STAT2 pin LED to turn on and remain on until charging is complete, thereafter turning off and STAT1 LED turning on to reprsent charging complete.

Could you please assist in where I have gone wrong with the design. My schematic was previously approved by someone on the E2E forum, however my PCB layout may be faulty with regards to placement distances or track thicknesses in certain places.

At this point I am limited to single side assembly of the PCB. Spaces outside of the yellow line boarders aroound the BMS and Charger sections are filled with other components, thus space is limited.

Is it critical to have dual sided placemnt of components for the charger IC as the datesheet mentions for PCB layout? I could look at stealing space on the rest of the board if certain tracks need to be made wider for current.

SCH_Schematic1_2023-09-18.pdfBOM_Remote Board_Schematic1_2023-09-18.pdf