A feedthrough assembly is disposable in an aperture of, for example, a power source encasement. In various examples, the feedthrough assembly comprises a ferrule, an insulator, a terminal conductor, and a sleeve. A portion of the terminal conductor extends through the ferrule thereby creating a portion internal to and a portion external to the encasement. The insulator is disposed within the ferrule and is sealably engaged with the terminal conductor portion extending through the ferrule. The sleeve is disposed over the internal portion of the terminal conductor and coupled thereto. In one example, the sleeve includes at least one notch on a sleeve first end or a sleeve second end, which may be used to weld or solder the sleeve to the terminal conductor. In another example, the sleeve includes a longitudinally extending void, which may be used to crimp the sleeve to the terminal conductor.