A method for harvesting energy from a high-G acceleration of a munition. The method including: proving a vibrating mass-spring unit in a housing of an energy harvesting device; and reducing an effective acceleration on the mass-spring unit by one or more of: offsetting the vibration of the mass-spring unit with respect to a direction of the high-G acceleration; biasing a mass of the mass-spring unit in a direction having at least a component in the direction of the high-G acceleration; limiting a vibration deflection of at least a portion of the mass-spring unit in the direction of the high-G acceleration; or limiting an amount of vibration of the mass-spring unit in a direction offset from the direction of the high-G acceleration and removing such limit after the acceleration.