Date of Graduation

12-2021

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Degree Level

Graduate

Department

Mechanical Engineering

Advisor/Mentor

Po-Hao A. Huang

Committee Member

Rick J. Couvillion

Second Committee Member

Xiangbo Meng

Keywords

Lithium-Ion, Small Satellites, Small spacecraft, CubeSat

Abstract

Li-ion batteries are widely used due to the large amount of rechargeable energy they pack into a small, light package. This higher energy density makes Li-ion batteries ideal for small satellite applications, specifically CubeSats. CubeSats have grown in popularity in higher level education due to the National Aeronautics and Space Administration’s implementation of the Cube Satellite Launch Initiative, making it easier and cheaper to conduct small, low orbit missions. Because these CubeSats are occupying the same space as a crewed spacecraft, it is imperative that they are safe. There are numerous reports of Li-ion batteries creating fires that result in injury or death.

The goal of this work is to establish testing setups and procedures that will give an accurate profile of the electrochemical properties of lithium-ion batteries. Ten of the tested batteries will be used as the secondary power supply on ARKSAT-1, a CubeSat mission being conducted at the University of Arkansas. These batteries will be monitored for level of self-discharge, thermal stability, capacity retention, vibration resistance, charge-discharge cycling behavior, and tolerance low atmosphere. The electrochemical properties of the batteries must meet various criteria to show that they will be stable and safe to use in a CubeSat.

During all testing, thermistors in a simple voltage divider circuit were used to monitor the battery temperatures. The initial prep of the batteries required removing manufacturer stickers and additional circuitry. The barren batteries were inspected for physical deformations and their volume and mass recorded. Next the batteries were placed under a constant load of 50 mA for 30 seconds to record their closed-circuit voltage. Then they were discharged to 3.6V and left to rest for 14-days. A circuit was built and automated with LabView to record the open circuit voltage of the batteries every hour for the 14-days period. Next a charge-discharge cycling test was conducted, which was used to measure the capacitance of the tested batteries. The batteries need to be checked for mechanical resistance to shock and low-pressure environments, but these tests are outside of the scope of this thesis. The physical dimension and capacitance measurements are to be reconducted after the shock and vacuum testing to verify that no physical damage or capacity fading have occurred.

These tests were created with the intent to be easily adapted to any commercial off the shelf battery, specifically non-space-grade batteries, to allow for more flexibility in the battery choices as electrical supplies on future ARKSAT missions. It was found that the cells tested for this thesis were able to meet the testing requirements as set forth by NanoRacks, a private company whose purpose is to provide other organizations with necessary services to conduct research projects in space. NanoRacks reviews the testing procedures created for this thesis and gives initial approval of the CubeSat missions so that they can be launched from the International Space Station.

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