This battery is a Panasonic 25.2V 13.2Ah Li-ion battery for an electric bicycle. It is 7 or 8 years old. When new, a full...

So… I tried everything from clean reinstalls, reseting NVRAM/SMC to blow the dust with a compressed air can....

I finally found SOLUTION and the real reason behind the heating…. DUST!!.. I was ready to send it for a real diagnostic / repair an decided to clean it from the outside a little. Took my vacuum cleaner and taped the bottom with plastic and duct tape as to only allow the vacuum to clean the small air intakes for the fan. Nothing came at least not much. Went to the store and bought pair of air dusters and used all of it in the same place, directly into the small openings with the air duster tube….. clumps of dust came rushing and after the cans ran out of air I used the vacuum to clean once more and this time a lot of fine particles of dust were visible. Booted the Mac and the first thing I noticed was the GPU Diode running at 39ºc while idle, instead of 60ºc and running CINEBENCH never made it run hotter than 80ºC. I always clean my Mac, with Air Dusters, even the air openings but never the whole can with the tube sealed directly into the aluminum.