is a bit confusing what the guy says but mainly what i understand from it is that you need to power up the cell and when it is disconnected it will be connected to a external coil having an incandecent bulb attached to it
it appear to me he try to take the back emf of the cell itself out generating power somehow,..
the cell is basically a resistor when water is very pure the voltage will be proportional to the amps flowing thru it
when water has a base or acid it will have free ions and their movement will cause a current to flow..
when we apply energy to a capacitor some energy is lost when charging it related to the resistive losses
there is even a situation possible to calculate when a charged capacitor is connected to another of the same size half the energy simply disappear mathematically however is not dissipated its a matter of destroy the electromagnetic energy such as happen with wave interference.. the back emf voltage itself stops the current when the capacitors reach the same level..
with inductor the voltage is not in the same direction because as i tried to explain before in other posts the inductor works by separating a charge density in the metal this causes the charges to have a attraction to each other inside the coil itself so when we disconnect the source they simply volktage go backwards but in the in the inductor case backwards is in the same direction for the electrons
nice one