The data line for the SMBus. Through this pin, the battery transmits crucial telemetry data to the laptop, including remaining capacity, cycle count, state of health (SoH), temperature, and manufacture date.
Never attempt to charge the pack by forcing raw DC voltage into the power pins without current limitations. Safe charging requires a CC/CV (Constant Current/Constant Voltage) profile matching the 3S configuration limits (Max 12.6V charging voltage). Hp Mu06 Notebook Battery Pinout Configuration