So just to clarify, aside from solid crud, do I need to worry about cleaning out around that post on the battery (like if some of the juice happens to get in there)? T-Pins... I would've never guessed, even though now it seems so completely obvious haha
You can, but it's really just about getting rid of the hardened black crud in there, and unblocking the air holes, so that you can make room for enough air in there (oh, yeah. Don't forget to poke the air holes. On auto batts, there are the two on the threads, and I think
two more on the post bottom that you have to feel around for through the ones on the threads). A dry, clear, crud-free channel = more air in there. Doesn't have to be pristine, just crud-free and dry. I usually just pour a little alcohol in the cap, swish it around with the batt, then shake and wipe it dry, but I hear alcohol wipes from WalMart are really good to have around. Use them like you would the paper towel. They're stronger, thinner, lint-free, and pre-dampened with alcohol. Alcohol is good for getting rid of the juice film that forms on the posts, which also obstructs contact. Water works fine too, but alcohol dries faster.
Oh, and wipe down the post on the charger too (with an alcohol-dampened Q-Tip or something) while you're at it.
But the one you "borked" should be an easy fix, right?
Oh, one more thing to check: remove the ashcap to make sure you don't have dust bunnies in there. This, and clearing the holes on the bottom of the posts, might improve your activation issue with that second auto.