The balancing of mechanisms consists in distributing their moving masses, inertias, and elastic components in order to achieve key mechanical properties, such as the elimination of the shaking forces and moments exported onto their supporting structure or the insensitivity of the mechanism to gravity and to the motions of its chassis. This article introduces a new refined systematic taxonomy for the classification of multi-degree-of-freedom (DoF) 3-dimensional passively balanced mechanisms. The taxonomy is composed of 15 distinct types – compared to only 4 types described in the literature. Each type is provided with its definition, the necessary conditions to be satisfied, the list of resulting mechanical properties, and a 1-DoF mechanism example. This taxonomy applies to mechanisms subject to gravity and mounted onto fixed or mobile chassis undergoing linear and angular accelerations, and, newly, also angular velocities. It is represented as a 4-set Venn diagram built on 4 primary balancing types: static, force, moment, and a newly introduced inertial invariance. This theoretical work allows for a refined categorization of the broad spectrum of balanced mechanisms while alleviating some inconsistencies observed in the existing literature.