Despite this circuit not being recorded as a patent, it has plausibly been attributed to the prolific genius of Nikola Tesla.
There is some conjecture that it may have been under the bonnet of Tesla's own electric car, a 1920's Aero, reputed to be capable of 90mph.
A transistorised version was exhibited by John Bedini, as the "cigar box motor". It was observed keep running without depleting it's battery.
The basic principle is relatively straightforward.
If you have two 12volt batteries in series you get 24volts.
Two 12volt batteries in parralell will be 12volts.
If you connect these four batteries together as a circuit either side of a load you will have a potential difference of 12volts.
A set of six oscilating switches between all four batteries will produce a very lumpy kind of alternating current (AC is well known as Tesla's invention)
The batteries are constantly replenishing each other because the series pair flash charges the parallel pair and vice versa.
The circuit can also be made using any combination of batteries and capacitors.