Improved interchangeable rechargeable battery system

A rechargeable battery system, including a housing, a negative terminal, a positive terminal, and a third terminal. The housing substantially encloses a rechargeable electrical discharge member such as an electrochemical electrical storage device. The negative terminal is electrically coupled to the rechargeable electrical discharge member and may be electrically coupled to the housing. The positive terminal is electrically coupled to the rechargeable electrical discharge member and electrically isolated from the negative terminal. The third terminal is electrically coupled to the negative terminal. The third terminal is also physically isolated from both the positive and negative terminal. A non-conductive sleeve substantially encases the housing and the negative terminal around which the positive, negative, and third terminals are externally exposed. Therefore, an electrical device configured to operate with either a rechargeable or finite battery may selectively detect the electrical voltage across the positive and third terminal rather than the positive and negative terminal and automatically adjust the electrical operation to correspond with a rechargeable battery.