Q: Battery and temperature problems

Did you perform a reset of System Management Controller using

instruction for your model portable within the Support article (?)

• Reset the System Management Controller (SMC) on your Mac - Apple Support

There are a few helpful Support articles that inform & instruct on

'about and how to' batteries, adapters, etc w/ Apple portables...

First one covers many topics -- including troubleshooting issues:

• About Mac notebook batteries - Apple Support

Power adapter and connection issues:

• Apple Portables: Troubleshooting MagSafe adapters - Apple Support

Other symptoms & issues that affect battery life and charging:

• Apps can affect Mac performance, battery runtime, temperature, and fan activity - Apple Support

There may be some curious issues where a problem only seems to

have arrived in the Mac after upgrade to a new system. A few are

mentioned that could relate to previous user account setting or a

third party application that does not work well in newest macOS.

Good luck in this matter!