UPS safety precaution - Thanks for the "heads up!!"

From: Summerland Amateur Radio Club Newsletter, 12/3/06 (NSW, Australia) Darren Mitchell, VK2AUX:

"DANGER - 240 VOLTS HIGH.

WARNING to those who tinker with 'UPS' (uninterrupted power supplies),

on some models the battery circuit may be at mains potential, (ie not isolated).
This may be lethal if you want to extend the leads outside the case so as to use a larger capacity battery while it is connected to the mains.