Accurate Battery Performance Modelling: The Key to Accessing a Truly Responsive Modular Small-Cell Concept

The AEA Technology (AEA) Small Cell concept allows an infinite range of battery sizes to be built up using the minimum amount of re-qualification. Furthermore, an extensive rolling stock of cells is held at AEA to ensure that future demand can be met without the need for programme delays due to cell manufacture lead-time. Batteries can be composed of modular blocks so that energy storage systems can be built up from common building bricks. This eliminates the need for qualification and minimises recurring battery cost. Such features have captured the mood of the small satellite community in the quest for a truly responsive space capability. However, the Small Cell concept can become even more responsive if battery-modelling software is leveraged. This paper demonstrates how. Batteries play a key role during spacecraft Integration and Test (I&T), as they are fundamental to the power subsystem and critical to spacecraft health and safety. Typically, spacecraft manufacturers procure a workhorse battery. This battery (as a minimum) is electrically representative of the flight model. This need for additional hardware has a cost and schedule impact so that its replacement by accurate battery modelling software is highly attractive. Moreover, mishandling during I&T can result in the need for additional workhorse batteries and schedule delays. It is therefore seen that, for the small satellite community to truly progress towards the rapid checkout of multiple spacecraft, accurate modelling tools are essential. For small satellites to meet the rapid deployment targets of the user community, interface standards must be agreed so that development time is minimised. Traditionally, spacecraft manufacturers have stipulated a minimum capacity to space battery manufacturers. However, many alternative definitions of capacity exist (both by battery suppliers and their customers) making performance comparison difficult. This slows down acquisition and design activities. It is proposed that the most intuitive way to express battery performance is by demonstrating that the minimum battery terminal voltage over life supports the operating voltage of all on-board avionics units. In order to demonstrate such performance for any given mission load profile, flexible and accurate software must be available. AEA have developed a software suite that allows battery performance to be predicted with an unparalleled degree of confidence. Battery configuration, mission duration, type (LEO, GEO etc) and operating conditions are input and the software outputs all key battery performance parameters including terminal voltage, current and thermal dissipation. Results are output in transparent form, directly accessible through common engineering tools such as EXCEL. Both AEA and our customers utilise the software and confidence is provided by the fact that software had been verified against long-term in-orbit telemetry. The use of modelling software approach expedites system design, battery requirements definition and design reviews.