A power supply control assembly, comprising: a power supply adapted to power a device; an input device configured to receive inputs associated with different characteristics from a user of the device; and a power supply circuit connected to the power supply, wherein the power supply is configured to discharge through the power supply circuit to power the device in response to receipt, by the input device, of an input associated with a first characteristic, wherein the power supply circuit comprises: (a) an electronic switch electrically connected to the power supply for controlling discharge of power from the power supply to the device, wherein the input device is electrically connected to the electronic switch for controlling a switch-on or a switch-off state of the electronic switch; (b) an indication device configured to display a level of charge of the power supply in response to receipt, by the input device, of an input associated with a second characteristic; and (c) a power measurement device electrically connected to the power supply, the power measurement device comprising a current sampling device configured to collect current during the discharge of the power supply, and wherein the power measurement device is configured to calculate the level of charge of the power supply including sampling, at a predetermined frequency, and integrating the collected current, wherein the level of charge of the power supply is calculated based on measuring an amount of energy consumed, and wherein the level of charge of the power supply is not calculated based on measurement of a voltage drop across the power supply. a power supply adapted to power a device; an input device configured to receive inputs associated with different characteristics from a user of the device; and a power supply circuit connected to the power supply, wherein the power supply is configured to discharge through the power supply circuit to power the device in response to receipt, by the input device, of an input associated with a first characteristic, wherein the power supply circuit comprises: (a) an electronic switch electrically connected to the power supply for controlling discharge of power from the power supply to the device, wherein the input device is electrically connected to the electronic switch for controlling a switch-on or a switch-off state of the electronic switch; (b) an indication device configured to display a level of charge of the power supply in response to receipt, by the input device, of an input associated with a second characteristic; and (c) a power measurement device electrically connected to the power supply, the power measurement device comprising a current sampling device configured to collect current during the discharge of the power supply, and wherein the power measurement device is configured to calculate the level of charge of the power supply including sampling, at a predetermined frequency, and integrating the collected current, wherein the level of charge of the power supply is calculated based on measuring an amount of energy consumed, and wherein the level of charge of the power supply is not calculated based on measurement of a voltage drop across the power supply. (a) an electronic switch electrically connected to the power supply for controlling discharge of power from the power supply to the device, wherein the input device is electrically connected to the electronic switch for controlling a switch-on or a switch-off state of the electronic switch; (b) an indication device configured to display a level of charge of the power supply in response to receipt, by the input device, of an input associated with a second characteristic; and (c) a power measurement device electrically connected to the power supply, the power measurement device comprising a current sampling device configured to collect current during the discharge of the power supply, and wherein the power measurement device is configured to calculate the level of charge of the power supply including sampling, at a predetermined frequency, and integrating the collected current, wherein the level of charge of the power supply is calculated based on measuring an amount of energy consumed, and wherein the level of charge of the power supply is not calculated based on measurement of a voltage drop across the power supply.