The electrolyzer shown is based on the common-duct series-cell electrolyzer concept originally developed and patented by William Rhodes, Ernest Spirig, Yull Brown and later refined by Bob Boyce, George Wiseman, etc… It uses an alkaline (NaOH, KOH) electrolyte to split distilled water into hydrogen and oxygen components very efficiently.
The produced hydrogen and oxygen gasses are not separated to separate containers, but kept mixed. The produced oxyhydrogen gas is a stoichiometric mixture of hydrogen (2 parts vol.) and oxygen (1 part vol.) and can be combusted in vacuum.
The combination of series-cell topology is very efficient, because it allows the cells to operate as close to their optimal cell voltage (1.47V) as possible. The electrolyzer runs fairly cool, at about 30-50 C depending on the current and electrolyte.
The electrolyzer shown in this report has about 80-90% total efficiency when all things are considered (ambient temperature, ambient pressure, accurate measurement of gas volume and current) when powered by straight DC. Pulsing (PWM) or modulation of the input voltage waveform could increase the performance further, as it is known that in the beginning of each pulse larger current flows than in the steady state condition, thus lowering the cell voltage needed to push thru a certain amount of current and increasing the efficiency slightly. There are also claims of various resonance phenomena (Boyce, Meyer, etc.) that supposedly dramatically increase the gas production rate vs. input current when the electrolyzer is driven with a certain type of PWM rich in harmonics. However, this author has not been able to replicate any resonance modes in any sort of electrolyzer.
The electrolyzer has 7 cells with a target input voltage of about 12.9-14.1Vdc depending on temperature. This makes the cell voltage about 1.85-2.0V.
Electrolyte in each compartment is practically isolated from other compartments, but thereare 3mm diameter electrolyte level equalization holes drilled in the bottom corner of each plate (staggered)