Under the car for the first time in forever. Trying to unhook the battery connection to clean it, but can't get a good angle. Tips?

Also, I'm thinking it may be condensation, it doesnt smell like anything, but on the transmission bolt heads, oil pan, etc, there'* a black liquid.

Back to car now, going to wipe down all the sludge I can find and then try the battery again. Tips will be appreciated!

Negative battery cable is a 1/2" ratchet, 13mm deep socket with say maybe a 6 inch extension. Positive would be a 1/4" ratchet with deep 13mm socket.

I've never done it huh?

damn, not long enough extension to do either one. Wiped all the gunk off both while still connected, but anymore work as far as that'* concerned will have to wait till next week.

Looking under right front fender, I see a canister(HVAC right?) When I touch the connector to it, just barely move it any direction, a hiss occurs. Is that normal? Or should I replace it?
(I know clogged HVAC/broke HVAC line leads to leaking, which I have, and no air out of main vents, also a problem, os while I'm under I figured I'd poke around and ask).

right front is passenger. That canister is the vacuum tank for the HVAC system. This line should lead into the cabin as a purple tube at the HVAC programmer. If you have vacuum to that purple tube, then you need to do the fix as outlined in another thread.

"Vents" by Jamestharp. I think the link to the nipple fix is on something like page 6 or 8