36*C with I9kfangui, fan set to "on @ 40, off @ 35".
Battery-AC makes no difference to me with my temp control running.
Intel suggests to lappy manufacturers to implement the integrated downstepping (12.5% increments) via the manufacturers choice of BIOS, at a temp of 99*C. (Ninety-nine!!!) They also don't fully gaurantee the internal thermal shut-down diode to work perfectly, but it's designed to shut the CPU down @ 125*C, which is just amazing to me.