From Youtube comments. It appears it's more advanced than just simple DC electrolysis:

Stan Meyer use different type of electrolysis, it is not like + and - on plates , he use pulses and hi voltage and low amps. He shake water molecule by frequency , it is not simple system. Electrolysis can be don two ways , like by Faraday way , this is simple way , + and - , hi amps, which is dead end or Tesla way , which more complicated and Stan Meyer system working based on Tesla way. All dry cells it is crap, which is working based on Faraday way ,waste of money and time, Ebay full of this junk, for this cells need add KOH to get hi amps , then this cells getting hot , as soon they getting hot this dry cells stop producing enough HHO , then they need to be clean from KOH , but main thing they take a lots of amps which totally opposite which try tell us Stan Meyer , they key to produce right way HHO need FREQUENCY, HI VOLTAGE AND LOW AMPS !!!

http://www.rivendellvillage.org/Stanley_Meyer_Resonant_Electrolysis_Cell.pdf