NOT when the source is a battery, you cannot make more energy OR maintain the same energy than what you started out with, that's my point, regulation is a battery thing the current source, explain how you keep 24 volts stable, if the current is depleting at a rate proportional to a heavy load. that's my point. not in relation to 90-250VAC input source but to a battery.
The source being a battery makes no difference: tons of regulated switching voltage regulators operate off batteries in cellphones, tablets, laptops, calculators, remote controls, cameras, UPS, cars, LED flashlights, etc.
Not sure where you take the "making more energy" bit from. If you want to drive a 40A 24V load from a 12V battery, the converter will need to draw 80A not counting converter losses regardless of whether it is a PWM, self-excited inverter or whatever else. No magically created energy there: V*A in = V*A out + losses.
The way a DC-DC switching regulator compensates for battery (or whatever its input source might be) droop is exactly the same way an AC-DC switching regulator compensates for the 10-30V ripple on its AC input filter capacitor between input peaks: it modulates its duty cycle to compensate for changes in input voltage.
If you want to design a double-forward switching regulator to step 10-14V battery input to 24V output, you need a transformer ratio of about 1:3 assuming you lose only 1V in both input and output components including wiring resistance. When the battery is fresh-off-the-charger at 14V surface charge, the PWM regulator would operate at about 32% duty-cycle per transformer half (64% for the whole transformer) and when the battery reaches 10V, the PWM should be at about 47% per half.