Mercedes Mechanic beat me to the grinding compound in a worn phillips head screw to get a better grip. An aircraft mech ( they remove a lot of phillips screws ) taught me to break loose a stubborn screw by tightening to break it loose, this saves a sharp edge to back out the screw. Use a screwdriver bit on a 1/4" speed handle for better push and leverage.

Also, to avoid losing a finger or arc welding your twisto-flex, remove watches and rings before working on batteries or anything electrical.

__________________
Jeff

97 E320, ours 217,000miles
91 190E 2.6 daily driver 242,000miles
74 MGB,mine 120,000?
2006 BE350/Proline 21, 50 hours