Dry Cell Dynamics: The Bobbin

Abstract

This paper is a study of the relation between ampere‐hour capacity and drain. To determine this relation, a simplified model of the bobbin is set up. Kirchhoff's law is applied to this model to determine how the current through the manganese particles is distributed. (Do the particles near the carbon, or near the edge of the core, or somewhere between, bear the heaviest load?) It is demonstrated that on light and moderate loads the current is distributed almost uniformly, i.e., each manganese particle suffers about the same "drain." Attention is then focused on the individual particle. Evidence is introduced which indicates that some diffusion process within the particle itself plays a dominant role in determining the behavior of a dry cell on moderate and light loads. Fick's law of diffusion is applied to this hypothetical process. Constant current tests are used to determine the parameters in the resulting equations and to determine their ability to describe the behavior of dry cells on these tests.