NOVELTY - The electrochemical device e.g. a fuel cell for mobile phones and lap top computers, comprises interconnected electrochemical units having a membrane electrode assembly arranged between a first conductive surface (oxygen electrode side) and a second conductive surface (fuel electrode side), an air breathing fuel cell, and a gas tight seal provided around the electrochemical unit by a hot set or hot melt adhesive. The first conductive surface includes a first conductive tab overlapping a second conductive tab of the second conductive surface of an adjacent electrochemical unit.    USE - The electrochemical device e.g. a fuel cell is useful for electronic appliances such as mobile phones and lap top computers.    ADVANTAGE - The electrochemical device e.g. a fuel cell is compact, simpler (without or less moving parts) and easily manufacturable at mass scale, has very low resistive losses and an improved form of interconnections between cells of the planar array of the fuel cell, and can able to allow easy integration with portable electronic appliances such as mobile phones and lap top computers.    DETAILED DESCRIPTION - The electrochemical device e.g. a fuel cell for mobile phones and lap top computers, comprises interconnected electrochemical units having a membrane electrode assembly arranged between a first conductive surface (oxygen electrode side) and a second conductive surface (fuel electrode side), an air breathing fuel cell, and a gas tight seal provided around the electrochemical unit by a hot set or hot melt adhesive. The first conductive surface includes a first conductive tab overlapping a second conductive tab of the second conductive surface of an adjacent electrochemical unit. The first and second conductive tabs are spaced apart from one another and substantially parallel to one another, and are electrically interconnected by a conductive material placed between the first and second conductive tabs. The conductive tabs include mating surfaces electrically interconnecting one another. The conductive surfaces are profiled for directing fluid flows between the surfaces and a membrane electrode assembly. The tabs extend beyond the flow field of the interconnect. The electrochemical units are formed around apertures in a nonconductive plate. The tabs are formed from coated copper material having a corrosion resistant covering. The electrochemical units are arranged in an array, are electrically connected in series, and are embedded in a non-conducting material layer. The non-conducting material layer comprises acrylic, plastic or ceramic material of predetermined thickness. The conductive material comprises graphite, a metal or a metallized surface of a non-conducting substrate. The first or second conductive surface includes fluid flow fields, which are machined, stamped, etched or molded into the surfaces that are coated with a corrosion resistant protective coating, which is formed by physical vapor deposition (PVD), spraying, electroplating or thermo-chemical deposition. The first conductive surface is formed from selective metallization on a non-conducting substrate. The overlapping conductive tabs include raised portions for making conductive contact with predetermined other surfaces. An INDEPENDENT CLAIM is included for a method of interconnecting a series of electrochemical cells to form an electrochemical device.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a serial electrical interconnection of a planar fuel cell.    Planar 8-cell stack (10)    Anode (11)    Cathode. (12)