Blog Post #1

Background & Motivation:

Lithium-ion batteries power a vast majority of electronic devices and systems. They are found in the majority of portable electronics, electric vehicles and some aerospace applications. That being stated, ensuring the safety, reliability, and longevity of lithium batteries remains a challenge. A report published by the Federal Aviation Administration highlights the importance of testing lithium-ion batteries to prevent safety incidents and optimize their performance. Lithium-ion batteries are especially used in aircraft and shipped as cargo. A battery failure can have catastrophic consequences such as fires as presented by the Federal Aviation Administration report. The development of a battery test chamber provides a medium that can safely simulate extreme test conditions. Furthermore, by collecting data on lithium-ion batteries near the point of failure, catastrophic events can be avoided since they will be expected and proper precautions can be taken.

Dr. Song is researching batteries’ characteristics near points of failure. These tests are to monitor the internal structure of batteries to detect any abnormalities using piezoceramics. One piezoceramic will send a signal through the battery while another one will collect the signal. Based on what is different between the two signals, this will correlate to the state of charge and state of health of the battery at the given time. In order to get data on the battery at a low state of health, Dr. Song will need to conduct tests on batteries near their failure point which will induce thermal runaway. The purpose of the battery testing chamber is to allow for these tests to occur in a safe manner.

Main Problems and Possible Goals:

When conducting battery testing and monitoring, it is convenient to have a proper testing chamber in the event the battery experiences thermal runaway and/or combusts. Furthermore, combustion is typically foreseen when pushing a battery to its limit during testing. This means a testing chamber is more than useful when conducting battery tests using high current rates. Team 20 is proposing to design and build a functional battery testing chamber that can provide a safe space to conduct battery tests and withstand any potential battery combustion that may occur during testing. This chamber will be designed to hold a maximum of four batteries at a time and will be around 2’ x 2’ x 2’ with a breaker box attached to a side wall of the testing chamber. The batteries the team will focus on are 18650 lithium-ion batteries. From previous tests, it is proven that thermal runaway begins at around 150℃ and continuously increases to upwards of 500℃ as a chemical reaction occurs between the components of the battery. Moreover, the pressure released from the battery during combustion is around 36.16 bar which means this pressure will need to be contained by the chamber until it can be released. The battery test chamber will also need to safely contain and disperse the harmful gasses produced from thermal runaway such as hydrogen, ethylene, and carbon dioxide. The main goals for the battery chamber are to contain the byproducts from the failed battery and disperse them in a safe manner that does not harm the user by being vented to a separate holding chamber, monitor the temperatures of the batteries, and notify the user when thermal runaway is occurring, and ultimately to keep the user out of harms way by keeping the chamber locked until all gas has been moved out of the main chamber.

Troubling Obstacles and Possible Solutions:

One major issue Team 20 anticipates is finding an accurate solution to being able to successfully displace toxic gas from the testing chamber, contain, and safely release it in a manner that is safe for the user. Team 20 will conduct further research to obtain a proper method of disposal for each of the gasses present in the chamber. A method of monitoring and validating the success of gas containment will need to be developed to ensure the chamber is not leaking.

Team 20’s proposition to dispel harmful gasses from the chamber is to attach an air pump system that pumps an amount of regular air that is a little over the volume of the main chamber into the secondary chamber. This air is denser than the harmful gasses that are produced during testing so it will get displaced into another chamber connected to the battery testing chamber. This separate chamber will collect the hazardous gas and can be safely disposed of at the user's discretion. Along with the air pump system team 20’s proposition to dispel harmful gasses from the chamber is to conduct a nitrogen purge of the main chamber. Once testing is complete nitrogen gas is pumped into the chamber to displace the toxic gas and replace the atmosphere in the chamber with nitrogen gas. Gas sensors will be applied to the chamber to detect any harmful gasses in the system and the chamber will not be able to open until the sensors no longer detect any of the gasses.

In order to test if the chambers can properly contain the toxic byproducts from the batteries, non-toxic gas can be used in the chamber and leaks can be checked for in the most susceptible areas using gas sensors. The second chamber that will be used to store and release the gas at a later time will also go through the same test. This test will give reassurance that the main testing chamber and secondary holding chamber can contain the toxic byproducts with no leakage.

Reference Figures:

Schematic of the battery testing chamber.

18650 Lithium-ion battery that will be used in the testing chamber.