Yes, though I just edited my post to correct "I would do this" to what I meant to say ... "I would not do this."
I've never done it, and wouldn't, but it should work. You may need to be watching the speaker as you make contact with the battery.
I once touched the rca with my finger with the amp hot (accidentally) .... it picked up enough ac to scare the h--- out of me. However, my sub amps have fixed gain so are always at max gain.
If I were to do this test, I would start with the sub amp gain quite low and raise it until I could see the cone move.