What part is responsible for the Battery Temperature?

I have Received a Samsung Galaxy a71 from my friend because it had a damaged screen which i successfully replaced, i was going to main buy whenever i tried charging it i got the Battery temperature to low/high to charge, upon disconnecting the battery i was able to boot from the power that my cable was providing, i installed DevCheck to see whats causing the issue and i saw that the battery temperature was at -20, which part is responsible for providing the battery temperature simce on the s8 it was the wireless charging coil (which the a71 doesn't have)

Thanks in advance and sorry for my bad english