If you look at many of the early designs by the big names in HHO you will notice that they were testing simple +- configurations of various types. If you put 12 volts across that, you generate heat. However, if you take and put 6 canisters in series with the same +- plate configuration you now have a plate gap voltage of 2 volts. So, yes in these early designs they did notice lower heat. However, it is still a poor design for efficiency. Best to go with the dry cell design.
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Some days I get the sinking feeling that Orwell was an optimist!