No, I understand you. You're describing an HHO fuel injection system powered by the alternator, not the battery. That still does not fix the problem, as there is no meaningful difference between engine->alternator->battery->electrolysis and engine->alternator->electrolysis for this analysis. You factually wind up burning more gas that way, not less.
please read again, and try to comprehend what i said.
You might be careful about using demeaning language like this. How will it look in retrospect if it turns out that you're the one who is mistaken about this issue?
from my original response: "let me explain. most of the energy from the fuel used in an engine is wasted as heat escaping from the exhaust and radiator. This heat can be directed to the hot side of a stirling engine. the stirling engine can produce electricity by recycling the heat energy that is normally discarded. this electricity produced using WASTE energy from the engine can be used to produce hydrogen gas using a simple electrolysis cell. the hydrogen can be used to supplement the normal petrol fuel supply."
did i mention taking power from the alternator?
No, that's simply the version of this idea I am most familiar with. I would apologize, except that you've been rude.
Waste heat recapture for automobiles is already an ongoing area of development. However nobody is doing it using stirling engines or HHO. Why do you suppose that is? Have they really just not thought of it?
i apologize if i seemed rude. i was simply saying what i meant as presicely as possible.. your response showed that you had missed the point i was making so i asked you to reread it carefully. that is all. no offense intended.
i don't see any waste heat recapture on my car. just hot exhaust and a radiator. oh well....
Not all cars have such systems. Those that do use methods of waste heat recapture that do not involve electrolysis.