Altider30

Ok, I went to deer camp this past weekend. I was listening to the ballgames on the radio while grilling out saturday night, and i probably drained the battery a little, but i got up to come home Sunday, and it started. (although it was a weak start) When i got home, i accidentally left headlights on, and completely drained battery. Battery was old, so i had intended on getting a new one. Went and got new battery, installed it, tried to make sure all connections was good. I got in truck, dash lights were bright, turned key, and it is like a dead short. All guages go down, all lights go off. And then slowly the voltage gauge starts to rise again. Here is the kicker. I can turn on the headlights, and a relay in the fuse box under the hood just clicks away constantly. Can this relay cause me not to get fire to crank the motor? I've heard replace battery cables, but they do not look that bad to me. Any suggestions?