How can I figure out cordless drill terminal polarities?
Based on an Instructables article about rebuilding a Black and Decker battery, it would appear they have chosen to use the outside terminal for positive and the inner terminal for negative.



In another part of the article, he shows another brand of battery that has a very similar terminal but the connectors are in a different position.  It's easy enough to just move the terminals as needed.

Of course, this might not be true for 100% of the B&amp;D line, but it's pretty good evidence.