Okay, this circuit seems to capture back-EMF and route it back into the circuit.
https://youtu.be/oWqsMoC6HDc?si=Ro-4-Ha6Op6Z3hJL
5:44 : battery voltage measured at 11.65 V
10:17: battery voltage measured at 11.70 V (went up in 4:30 powering a load even)
12v lead acid battery strength is determined by the voltage level, so voltage going up = battery getting charged
This circuit seems monkey-simple to put together even ... A circuit you could give to an engi and have him dev something serious up with
He lifts the wooden base up in convincing ways as well.
Added split video in zip form, just delete the .zip ending and open 001 as archive to get the youtube video.
Video part 2
Video part 3
Video part 4
Final part.
I posted the vid just for posterity, this place seems to keep on tickin' but the youtube accounts and vids tend to vanish after some years...