Where to start looking....

67Dart273, very possible about the Tender gone bad.
I fully charged the battery (13.5V), and before I connected the positive battery cable took one last look at the terminal ends. Seems the positive end has a small crack in it, so I replaced it.
Per your instructions above, I connected positive cable, and hooked test light in series to the negative cable. No good light, just a quick flash of light. So I then checked for V in series, and it finally came down to .939V.
I then disconnected the positive cable and check battery V, that had come down to 13.2V. Should the Voltage of the battery drop/drain that quick?
Everything on the car is disconnected right now, including the fuel pump & relay, Tender, etc., and the key is out of the ignition. Where to next?
Thanks for any help on this!
Steve~