Lithium cell having depletion gauge

A lithium cell comprising:

• at least one cathode member positioned within a conductive housing and having two major surfaces, one of which is in direct electrical contact with said conductive housing;
• an insulative separator being positioned against an outer major surface of said cathode member;
• a first lithium anode of a predetermined thickness having first and second major surfaces, said first major surface thereof being positioned adjacent to said insulative separator, said second major surface of said first lithium anode having a stepped portion;
• a second lithium anode of a predetermined thickness having first and second major surfaces, said first surface thereof being positioned adjacent to said second surface of said first lithium anode over substantially the entire surface area of said second surface of said first lithium anode;
• a first electrical sensing conductor positioned between said surfaces of said first and second lithium anodes in a region defined by said stepped portion of said surface of said first lithium anode, said first electrical conductor being in electrical contact with said first lithium anode;
• an insulative pad interposed between said first electrical sensing conductor and said second lithium anode;
• said second major surface of said second lithium anode having a stepped portion;
• a third lithium anode of a predetermined thickness having first and second major surfaces, said first surface thereof being positioned adjacent to said second surface of said second lithium anode;
• a second electrical sensing conductor positioned within said gap between said surfaces of said second and third lithium anodes, said electrical conductor being in electrical contact with said second lithium anode;
• an insulative pad interposed between said second electrical sensing conductor and said third lithium anode;
• a first anode lead electrically connected to said first and second electrical sensing conductors, said anode lead extending out of said conductive housing and being electrically insulated from said housing;
• said first electrical sensing conductor coupled to said anode lead so that a first electrical potential is developed between said first electrical sensing conductor and said conductive housing until said first lithium anode is consumed by discharge of the cell to thereby provide a first indication of a predetermined level of discharge of the cell;
• said second electrical sensing conductor coupled through a resistor to said anode lead so that subsequent to the depletion of said first lithium anode a second electrical potential is developed between said second electrical sensing conductor and said conductive housing until said second lithium anode is consumed by discharge of the cell to thereby provide an indication of a predetermined level of discharge of the cell;
• and a second anode lead electrically connected to said third lithium anode, said lead extending out of said conductive housing and being electrically insulated from said housing.

An electrochemical cell comprising:

• an outer conductive housing;
• a cathode material inside said housing and in direct electrical contact with said housing;
• at least first and second adjacent lithium anode materials inside said housing and spaced from said cathode material by porous insulative separator saturated with an electrolyte;
• a first anode lead;
• first and second electrical sensing conductors connected respectively to said first and second anode materials;
• a resistor coupling one of said first and second electrical conductors to said first anode lead;
• said other electrical conductor being directly coupled to said first anode lead;
• a first voltage potential being developed between said first anode lead and said conductive housing through said first anode material until said first anode material is consumed and said first conductor is no longer in electrical contact with any anode material and a second voltage potential then being developed between said first anode lead and said conductive housing through said second conductor, said second voltage potential being different than said first voltage potential as a result of said resistor being coupled between one of said first and second conductors and said first anode lead, and said different second voltage potential indicating a predetermined level of discharge of said cell.