As hybrid and electric vehicles continue to grow in popularity, automotive manufacturers strive to drive down the costs of the lithium-ion battery packs that power them. At the heart of every battery pack design is the choice of what battery cell is right for the job. The features of the selected cell have far-reaching consequences for the characteristics of the final pack and the cost thereof. This paper builds off of two prior simulation-based studies in order to form an analytical framework for predicting the effects of lithium-ion cell size on the cost of air-cooling in aligned battery packs. The findings of this paper validate the conclusion that for a given set of pack requirements, a cell size that minimizes cooling cost can be found. As long as the necessary assumptions are satisfied, the presented analytical method can effectively be used to predict the minimum cost cell size for cylindrical cells in crossflow.