So, I'm sure you've wondered just how much power is contained in a NdFeB (Neodymium-Iron-Boron) permanent magnet. To know that, we'd have to nearly instantaneously destroy the magnetic domains and measure the output power.
Fortunately for us, there are scientists just crazy enough to do just that. It's formally known as 'shock depolarization of ferromagnetic materials". It involves explosives.
It was experimentally demonstrated that miniature explosively driven shock wave ferromagnetic generators (FMGs) containing Nd2Fe14B hard ferromagnetic elements possessing high (BH)max generate output currents with amplitudes up to 5 kA [6, 7, 9] and output voltages with amplitudes up to 50 kV [7, 10, 11].
This occurs over ~6.2 nanoseconds.
50,000 volts x 5,000 amps = 250,000,000 watts
6.2 nanoseconds is 0.0000000000017222222 hours.
So that works out to 0.00043055555 watt-hours.
An Energizer AAA battery has ~1.87 watt-hours capacity.
What does this mean? Well, the Motional-EMF devices (Gunderson, Sweet, Flynn, etc.) cannot be getting their energy from the magnet itself... and that leaves only one other place they can get that energy... the quantum vacuum.