Abstract: A modularized power supply is presented employing individual electrochemical cells which are rendered inert when separated from a specified unlocking circuit. The cells are enclosed in a cell module having a disabling circuit which isolates the cell terminals and prevents release of significant cell energy. A switch in the disabling circuit is activated when the cell module is connected to the specified unlocking circuit in an external frame. The frame includes receptacles for receiving multiple modules, all of which must be connected before power is delivered to a host interface. The frame may include circuits and devices for monitoring the performance of the modules, for controlling cell charging and discharging, and protective elements to protect the modules and tray from aberrant conditions such as high temperatures, overcurrent, and similar events. By including these in the frame, fewer elements are required in the individual modules, reducing their complexity, weight and cost.