Advanced Battery Models from Test Data for Specific Satellite EPS Applications

Abstract

Detailed battery models are required for accurate Electric Power System (EPS) simulations of satellites in various LEO, MEO, and GEO missions. Older and outdated models had used various power margins to over-estimate the size and weight of the satellite EPS for a given mission. Today's models incorporate the use of databases of battery test data from various testing facilities to much better and more accurately predict past, current, and future mission battery behavior. This paper describes various battery types, cell types, a database of data that have been collected and analyzed, and overviews the detailed models that have been developed for applications from that data. The battery models include Nickel Hydrogen, Lithium Ion, and Nickel Cadmium battery cells. Independent variables for these models include capacity, number of cells, charging and discharging, charge and discharge rates, temperature, and battery cell age. Model options also include cell dropouts vs. time, and variable sensitivity analyses. These models have been benchmarked to their corresponding data, and have been implemented into various simulation studies for various missions, such as for the Hubble Space Telescope battery depletion problem. The use of these models provides much more accurate simulations of EPS behavior, battery degradation, and lifetime estimates that are needed in the Aerospace Industry today.

The Adverse Effects of Not Including Capacity Addition During LiIon Taper Charging in EPS Sizing for LEO Missions

“…Descriptions of the development of this PTS code and its results have been presented at several IECEC and Space Power Workshop conferences in recent years. [1][2][3][4][5][6][7][8][9][10] The Power Tools Suite codes package originated in the late 1990s for use in the Iridium Program and in other specific programs within Lockheed Martin. [11][12][13] The Models and Codes have been significantly updated several times during the past few years and have been displayed at a recent Lockheed Martin Corporate joint Space Systems Company and Advanced Technology Center modeling and simulations conference.…”

“…The PTS Dynamic Code contains all of the EPS Component Models and the ability to connect the models in any EPS configuration. [5][6] The numerical solution algorithm has been carefully written to provide numerical convergence on the voltage and current values within the EPS for any conditions: temperatures, solar array input parameters (e.g. light intensity, insolation or insol, angle), battery conditions (e.g.…”

“…Additional information on the various PTS EPS component models, and the EPS bus designs that have been modeled, can be found in previously released IECEC and Space Power Workshop papers. [1][2][3][4][5][6][7][8][9][10]…”