Abstract: A method of performing an electrochemical reaction in an electrochemical cell comprises electrodes separated by a membrane capable of taking up an electrolyte, the method comprises introducing into the cell a fuel or other oxidisable component and an electrolyte, and oxidising the fuel in the presence of an acid or alkali. Alternatively or in addition, usage of fuel may be monitored by including a reactant that is capable of undergoing or imparting a change in visual appearance on oxidation or reduction; and monitoring any change in visual appearance.

Abstract: A dc-dc converter comprising a power conversion circuit for converting an input voltage to an output voltage is described. A control circuit is adapted to drive the power conversion circuit so as to produce the output voltage at a predetermined magnitude.