The use of volume-agglomeration for introducing one or several levels of coarse grids in an Additive Schwarz multi-domain algorithm is revisited. The purpose is to build an algorithm applicable to elliptic and convective models. The sub-domain solver is ILU. We rely on algebraic coupling between the coarse grid and the Schwarz preconditioner. The Deflation Method and the Balancing Domain Decomposition (BDD) Method are experimented for a coarse grid as well as domain-by-domain coarse gridding. Standard coarse grids are built with the characteristic functions of the sub-domains. We also consider the building of a set of smooth basis functions (analog to smoothed-aggregation methods). The test problem is the Poisson problem with a discontinuous coefficicent. The two options are compared for the standpoint of coarse-grid consistency and for the gain in scability of the global Schwarz iteration.