My dad taught me a similar trick when I was young about 25 or so years ago. He used to call it shocking the nicad battery back to life. I/We have saved many nicads batteries that way. Only difference is we had a variable voltage power supply to use and we didn't tap it 6 or so times, but just held the high voltage on the terminal for about 1 second. Then measured the dead batteries. If the voltage moved from negative to positive then it was good to charge. If it was still negative, we'd zap it again for about a second and measure again. Anyway, I'm over nicads already. Lithium all the way. LOL
One question: Is the idea to double the voltage you apply to the dead NiCad (some of my older batteries are 9.5vdc) or does it take a full 36VDC to shock it back to life no matter the voltage stated on the dead battery?