So i came across over a dozen amb rechargable transponders. Obviously the batts are shot in them. Is there a way to wire them to plug into a receiver? I tried with one and it didnt fair very well lol.

They require 3v to charge the internal 3v NiCad cell, Running off the 6v BEC may damage them.

You would be much ahead ($$ wise) just to sell these and buy yourself a new transponder. These are not made anymore and are in relatively high demand.

With a 78L03 voltage regulator it is esy to power them from a higher voltage. I think even a Zener diode can do the trick.