Hydrogen efficiency from DC electrolysis?

Follow the link below for a detailed description of how to build an energy-efficient electrolyzer (test results included; 80-90% efficiency claimed). This design uses DC or AC electrical current to split water into a stoichiometric (2:1) mixture of hydrogen (H2) and oxygen (O2) gases. Since this mixture (referred to as "hydroxy", "egas", and "Brown's gas" by "water-fueled car" enthusiasts) just needs a spark to DETONATE LIKE A BOMB, I don't recommend this particular design! Collecting the H2 and O2 in separate containers would be much safer (though still unsafe for amateurs). I only mention this article because the author seems to have done a good job of finding the conditions for optimal electrolytic efficiency.

http://www.waterfuelcell.org/WFCprojects/Tero/series_cell_v1.2.pdf

Nice info. Looks super and a great design.

What if there was no bridge rectifier or pulse wave and it was straight off a car battery using the design shown from the pdf? What do you suppose the efficiency would be over a short period of time at 70 degrees F for say a minute or two?

What if there was no bridge rectifier or pulse wave and it was straight off a car battery using the design shown from the pdf? What do you suppose the efficiency would be over a short period of time at 70 degrees F for say a minute or two?

Difficult to predict in advance. The overall energy-efficiency depends on so may different factors -- you would need to ask people who have done many experiments. I have done a few preliminary experiments with very simple 2 volt DC-powered electrolyzers, and achieved efficiencies in the neighborhood of 75%. And I have not even optimized the system yet (I could have used nickel electrodes, and a higher concentration of KOH). So decent efficiencies seem attainable. But I have done very few experiments, so I don't know how reproducible my results are. What application do you have in mind, if you don't mind me asking?