atb here is a video you should take a look at if you get a chance. The metal is so thin around the post as you now know, it's probably best to use this method for cleaning your batteries. It's quick, safe, and best of all the connectors look brand new afterwards. The metal around the post is probably safe using a safety pin, but I think you'll find this method is better at cleaning. As well you might also want to dab a little alcohol or just use a dry Q-tip and wipe off the connector on your charger(s).
Hope this helps you atb!!!
