| Summary: | PicoSat is a notional miniature (pico-) satellite concept that includes a low-voltage custom-manufactured Lithium-ion pouch (secondary) battery cell sandwiched between two Silicon wafers. It is imperative to evaluate the performance of the battery cell in a simulated space environment to determine its suitability for the PicoSat concept and identify any potential issues (such as due to the swelling of the battery cell pouch) during the operation of the satellite with the battery cell in space.
In this thesis, an approach to non-destructively evaluate the performance of a Lithium-ion pouch battery cell for space applications is demonstrated. First, the fundamental capabilities and the setup required to test a low-voltage Li-ion battery cell are developed. Such fundamental capabilities include the ability to charge and discharge a low-voltage battery cell at a controlled rate and the ability to control the temperature of the battery cell-under-test. These capabilities are fundamental as they may be used on a variety of low-voltage secondary battery cell chemistries intended for pico- or nano-class satellites regardless of the form factor of the cells. Next, capabilities specific to testing the custom Li-ion pouch battery cell for the PicoSat concept are developed. Such capabilities include estimating the pressure variation inside the battery cell pouch and charging of the battery cell using simulated photovoltaic cells in a simulated space environment. Finally, the results of the performance evaluation experiments are presented along with the analyses.
The performance of the battery cell was evaluated during charge-discharge cycling at fixed operating temperatures in the range, [-40 degrees C, 50 degrees C], during three-week storage at an elevated temperature (with no charge-discharge cycling), and in simulated low-earth orbits. It is concluded that the battery cell is suitable for use on a PicoSat-type satellite as the cell attained a steady capacity-positive (in mAh) operating state in simulated orbits. Although an increase in the cell pouch pressure was observed in all experiments, the extrapolated pressures over 365 days were estimated to be orders of magnitude below the fracture strength of Silicon wafers and the ideal tensile strength of Silicon as found in literature.
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