If you get a relay with a normally closed contact, It is a no solder no electronic knowlefge needed example of the collapsing spikes. When hooked to a oscilliscope the spike range up to 400 volts and frequency is the natual resonant frequency of the relay mechanism. It can be used to de-sulfate Lead acid Batteries, and rejuvinate ni-cad batteries that normally do not take a charge any longer. The possibilites for this project are still being discovered and are wide spread. Patrick Kelly has expanded on this circuit in his latest book.
ExampleRelay = 100 unit at 5 HzSolid state = 1 unit at 5000HzThe end result is relay produce 500 unit a second where solid state produce 5000 unit per second. Solid state win. In term of reliability and noise production, solid state version win too.My solid state conventional efficiency is at least 45% now.Here is my video showing spark when adding car coilYouTube - Unwanted spike in a relayI have two circuit, but I forget which one I use in video.