Effective resistive drain design considerations for Ni-H2 batteries and related battery support equipment

This work discusses some fundamental design parameters associated with both spacecraft batteries and commonly used battery cell resistive drain techniques. Also discussed are recommended methods to minimize the possibility of imposing excessive inadvertent and/or intentional reversal voltages across cells within the battery. Often overlooked, or at least not adequately considered, in the battery design and development phase is the effect of the battery design on the ability to efficiently discharge and remove the hydrogen in nickel precharged nickel-hydrogen (Ni-H₂) battery cells during routine, or planned, reconditioning. Coupled with the battery design considerations are also those concerns associated with the support equipment used to perform the resistive drain of the batteries. Attention paid to the design details associated with the effective resistive draining of the battery cells will lower the damage risk that may potentially be associated with this procedure. One of the most serious concerns often encountered in practice during resistive drain is the inadvertent, or excessive, voltage reversal of Ni-H₂ battery cells. Also, there is significant evidence that when Ni-H₂ battery cells are reversed for a prolonged period and/or for consecutive operations, a subsequent permanent loss of useable storage capacity as well as the potential for a shortened on-orbit life span could be experienced. This paper is primarily aimed at battery designs utilizing either individual pressure vessels (IPV) or common pressure vessels (CPV) and is not intended to examine single pressure vessel (SPV) Ni-H₂ battery designs (although the basic design principles discussed Are still applicable).