NOVELTY - Use of system in appliance comprising solid state rechargeable battery cells is claimed. The system comprises stack of electrochemical cells (10) comprising substrate (12). The substrate comprises surface region, positive electrode material with transition metal oxide or transition metal phosphate, solid state layer of e.g. ceramic or polymer, negative electrode material and electrically conductive material. The positive electrode material comprises positive electrode layer. The negative electrode material and electrically conductive materials are present on positive electrode material.    USE - The system is useful: in at least a vehicle, smart phone, cellular phone, radio or other portable communication device, laptop computer, tablet computer, portable video game system, an media player 3 or other music player, camera, camcorder, remote control car, unmanned aeroplane, robot, underwater vehicle, satellite, a global positioning system, a laser rangefinder, a flashlight, an electric street lighting and other portable electronic devices; and as a vehicle propulsion system to power a hybrid vehicle drive train.    ADVANTAGE - The system utilizes: solid state battery that exhibits energy density of 300 Wh/l, eliminates the occurrence of internal circuits; battery cells or electrochemical cells that have energy densities of no more than 50 Watt-hours per square meter, energy densities of at least 700 Watt-hours per liter, specific energies of at least 300 Watt-hours per Kg, achieve at least 5000 cycles while being cycled at 80% of the rated capacity and having gravimetric energy densities of at least 250 Wh/kg; and solid state rechargeable battery cells having greater than 80% capacity retention after more than 1000 cycle.    DETAILED DESCRIPTION - Use of system in an appliance comprising many solid state rechargeable battery cells configured to power the appliance is claimed. The system comprises a stack of electrochemical cells (10), each formed overlying the surface of a substrate (12). The electrochemical cell has an overall thickness of less than 50 mu and comprises a substrate less than 10 mu in thickness shortest axis. The substrate comprises a region, a positive electrode material comprised of a transition metal oxide or a transition metal phosphate and having thickness of 0.5-50 mu , a solid state layer of a ceramic, polymer, or glassy material configured for conducting lithium or magnesium ions during a charge and discharge, where the solid state layer has a thickness of 0.1-5 mu , a negative electrode material configured for electrochemical insertion or plating of ions during the charge and discharge and having thickness of 0.5-50 mu and an electrically conductive material coupled with the positive electrode material and free from contact with the negative electrode material. The layers of positive and negative electrode materials each have a total surface area greater than 0.5 m, where the substrate is made of at least a polymer, a metal, a semiconductor or an insulator. The positive electrode material comprises a positive electrode layer. The negative electrode material comprising a negative electrode layer and the electrically conductive material comprising an electrically conductive layer are present up on the positive electrode material. The positively electrode layer, solid state layer and negative electrode layer are continuously wound or stacked up on the electrochemical cells.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the solid state battery.    Electrochemical cell (10)    Substrate (12)    Cathode current collector (16)    Anode current collector (18)    Cathode material (20)