I went to start my Explorer the other day, and the battery was dead
from sitting so long.

I put a battery charger on it, but I'm not getting anything...zero
amps on the charger.

I've sanded all the corrosion from both contact points, down to shiny
bare metal...still nothing.

I also have a battery tender, so I put that on. It has an LED to
indicate charging...it's not lit.

Does this mean the battery is done for?