I put the MBP away in its neoprene sleeve to charge the battery while I had a cup of tea. Came back into the bedroom 40 minutes later & I could hear a hissing sound.
The fan had ramped up to over 7200 rpm to deal with Enclosure base temperatures of up to 43℃.
It’s cooled down now, the fan speed is under 1500 rpm & temperatures are much lower.
