Change the battery cable, or at least file the slot in the terminal where it can get a tight pinch on the battery post. A band-aid fix like a shim simply adds another layer of material to corrode.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!