Lithium-ion Battery Testing Chamber
Blog Post #2
Technical Problem Statement and Constraints:
The physical constraints can be divided into two separate categories, safety and functionality. For the safety constraints, the main properties are temperature, gas volume, and pressure. The chamber must withstand 600 ℃ from battery testing and be able to detect the occurrence of thermal runaway at 150 ℃. The temperature increase happens rapidly and Figure 1 shows how quickly it happens. Moreover, the chamber must also be able to hold 4 liters of gas byproducts and transport this gas to its secondary chamber with 0% leakage. Lastly, the byproducts will be released from the battery at an approximate pressure of 36.16 bar. Figures 2 and 3 show the opening at which these byproducts will leave the battery and how much gas will be released.
For functionality, the chamber must accommodate both forms of battery testing that will be conducted. Testing of the batteries will be done with a battery tester and with piezoceramics on the surface of each battery. To do both forms of testing simultaneously, each battery will need 2 wires for the battery tester and 4 wires for the piezoceramic testing. This leads to a total of 6 wires per battery for a total of 24 wires total since 4 batteries will be allowed in the chamber at any given time.
When working on the design, the initial challenge will be to find a material that can withstand temperatures such as 600 ℃. This material will also need to be able to withstand the pressure being released from the battery as well. While materials that meet our constraints do exist, the cost of these materials will be important as it has to be below our budget. For the contaminant and the transfer of the gas, a ventilation system will need to be designed. This ventilation system will need to move 4 liters of gas from the main chamber to the secondary chamber. This means the dimensions of the ventilation system and the fan to move the gas will depend on the type of gas being transferred and the volume as well.
Lastly, some of these physical constraints will be met with the use of a microcontroller and measuring instruments such as gas sensors and thermocouples. When designing the electrical system of the Lithium-ion testing chamber, Team 20 will see how much programming and work will be needed to actually implement the system they have in mind. This means starting the ventilation system and locking the main chamber door at 150 ℃ based on the measurements from the thermocouples and unlocking the door once the gas sensors return a negative signal. This task sounds achievable based on the team's qualifications, but as the design process begins, it may seem more difficult than expected. For an overview of all the constraints, table 1 has been included.
Table 1: Physical Constraints of the Lithium-ion Chamber
Figure 1: Temperature and Pressure over Time
Figure 2: Lithium-ion Cell After Thermal Runaway
Figure 3: Volume of Gas Created During Thermal Runaway
Technical Analysis Plan:
Team 20 has a technical analysis plan to address key challenges such as high temperatures, pressure increase, and gas containment and removal. First, The chamber will have to operate safely under an ambient temperature of 600 ℃. The high temperature is a product of triggering the thermal runaway of lithium-ion batteries, which starts at a temperature of 150 ℃ and could reach up to 600 ℃. The first analysis to be conducted is a material selection analysis. The analysis involves evaluating various materials based on their properties, cost, and availability. This analysis will address the material needed to withstand extreme temperatures without deformation or change. A finite element analysis will also be carried out after a CAD design of the chamber is finished. The FEA will include a thermal analysis providing valuable insights into how the material and overall chamber structure performs under different thermal stresses. It’ll specifically tell whether the material will experience thermal expansion or not. Findings from these analyses will determine the suitability of the material chosen for the chamber before it is built. The second challenge is the containment and removal of the harmful gases produced by battery thermal runaway. Up to 4 Liters of various toxic gases such as carbon monoxide and hydrogen fluoride, will need to be initially safely contained in the main testing chamber. These gases will then need to be moved to the exhaust chamber. A gas flow analysis using Bernoulli’s equation will be used to verify that the gases will move to the exhaust chamber as intended without returning. It’ll also be used to analyze and predict the behavior of gases in the system. Lastly, a structural analysis will be performed on the chamber to ensure that the internal pressure built up inside the chamber will not cause deformations or ruptures.
Soft Challenges:
Team 20 anticipates struggling to provide an accurate and detailed explanation of project outcomes. Team 20 has done sufficient work to better understand the physical problem it is attempting to address, which has allowed the team to develop a list of tasks and milestones that explain the flow of the project plan. Team 20, however, is still missing a lot of the “how?” when it comes to how the team will conduct/complete each task and milestone listed in the project plan. Team 20 will need to overcome the deficiencies in the prose in order to successfully convey and communicate its success.