Modular power supply for use in a weapon mountable designator/illuminator unit

1. A method of using a weapon-mountable designator/illuminator unit adapted for mounting on a weapon, the designator/illuminator unit comprising a light source adapted to generate a light beam emitted in a direction away from the designator/illuminator unit and is variable between a collimated light beam and a divergent light beam for, respectively, designating a target and illuminating a target area of the weapon, the designator/illuminator unit comprising at least a first modular power supply, the first modular power supply comprising:

a cage having first and second ends and defining a compartment therebetween that is adapted to receive a power source, the first end of the cage being adapted to be received within the designator/illuminator unit when the first modular power supply is assembled therewith; and

an end cap affixed to the second end of the cage and adapted to be exposed when the first modular power supply is assembled with the designator/illuminator unit;

wherein the first modular power supply is adapted to deliver power from the power source to the light source of the designator/illuminator unit, the method comprising:

operating the light source of the designator/illuminator unit with the power source of the first modular power supply to generate the light beam;

varying the light beam between the collimated light beam and the divergent light beam to, respectively, designate a target and illuminate a target area of the weapon;

removing the first modular power supply from the designator/illuminator unit;

installing a second modular power supply in the designator/illuminator unit; and

operating the light source of the designator/illuminator unit with a power source of the second modular power supply to generate the light beam.