I don't know if it works or not, but this idiot is full of BS.
Of course the second law of thermodynamics would apply in a waste free system. However, the alternator on your car is turning whether the battery is being drained or not. The load on the engine is lighter when the alternator is not charging the battery, but the load does not go to zero. This is lost energy. If this energy is captured by increasing the throughput of the battery, and fed back into the engine in the form of hydrogen, you have not created more energy in the system, you have simply reduced waste.
If this smartass want to shoot his mouth off, he should construct a true scientific experiment with controlled variables and present the results for peer review. Anything less is crap and he should shut up. We don't need educated idiots mucking up the water.