Qualification of a modular Li-ion battery pack for LEO Satellites based on cells not specifically designed for space applications

Abstract

Nowadays, space market considers the development of Small Satellite as a key factor for LEO missions evolution. One of the main characteristics of these missions is the combination between performance achievable and low mission costs. It is then extremely important to reduce mission expenses and one aspect of paramount importance, when lowering development costs, is the use of technologies not specifically developed for the space environment. In this context, S.A.B. Aerospace started a project for the qualification of a modular battery pack equipped with elementary cells based on a Lithium-Cobalt (LiCoO2) electrochemical system, which are not specifically born for space applications. The fundamental element of the battery pack is called “Module”: it integrates 8 Li-Ion cells connected in series and it is equipped with a PCB for passive voltage balancing. The modular concept allows the maximum versatility, satisfying power and energy demands for many different spacecrafts, depending on the number of integrated modules. This project is the follow up of the initiative undertaken to develop a battery pack for LARES (Laser Relativity Satellite) mission within the VEGA Launcher maiden Flight. Being the lifetime for the payload separation way shorter than in orbit servicing, a delta development is needed to show the compliance to Satellites missions. Thus, an innovative and accurate method to predict the available EoL (End of Life) capacity has been defined to show the suitability to the specific applications. Such method is based on the correlation between data collected from an Accelerated Lifecycle Test and mathematical method solutions. In this way, it is possible to set-up a test performing about 20% of duty cycles carried out from the battery during its overall lifetime, using maximum allowable charge/discharge rate to accelerate the capacity fading rather than a thermal chamber. After Accelerated Lifecycle test execution a Nominal Lifecycle test will be carried out, in order to investigate capacity fading effects on the battery with respect to the real power mission profile.