Lithium Ion Battery Aircraft Safety: Engineering Dunk Tanks for Testing

April 29, 2024 - Author: Brandon Degner - Lead Mechanical Engineer

Project Features:
Customized Dunk Tank Design, Thermal Runaway Battery Dissipation Capability, Hydraulic Submersion System

Lithium ion battery aircraft safety

The Challenge

A leading aerospace company specializing in the production of lithium ion batteries for their aircraft sought a aircraft battery test systems solution for safely handling thermal runaway battery hazards during lithium ion battery aircraft testing and production. The company approached ACS for a reusable submersion mechanism that could operate without electric power. This mechanism is needed to facilitate a quick and controlled delivery of the 150-pound batteries into a saltwater solution with minimal human intervention.

The tank’s dimensions and capacity specifications were crucial for safely containing and dissipating the battery’s energy during a thermal event. The difficulty resided in finding the precise amount of water needed to fully immerse the battery and halt the thermal event.

Since there are no industry standards for thermal energy release in lithium ion batteries, this calculation can be complex. Insufficient water in the tank risked overheating and water loss due to it boiling off, jeopardizing safety. Precisely calculating the tank’s size was also imperative to ensure the tank held sufficient water to absorb the battery’s energy but not so much that the battery volume would cause a hazardous material spill.

The aerospace company wanted two tanks: one positioned at the juncture of the assembly line conveyor, immediately following a welding station—a critical point prone to potential breakdowns in the production process. Additionally, they desired another tank to be stationed within an R&D lab adjoining the production floor. This strategic placement would facilitate swift transportation of malfunctioning batteries via carts, enhancing operational efficiency.

The Solution

The ACS engineers had to consider numerous variables, such as the battery’s design, materials, thermal management, and potential failure modes, that influence the amount of thermal energy that could be produced. The client’s selection of saltwater also impacted calculations based on the level of impurities in the water. Working closely with the client was crucial to tackling the lack of industry standards for predicting the potential release of thermal energy from the lithium ion battery in an event.

Based on their calculations and review by the aerospace company, the ACS team designed and fabricated two identical dunk tanks capable of dissipating 75.4 kWh of energy without raising the water temperature above 140°F, which keeps the tank surface temperature safe for human interaction.

One tank needed to accept a battery directly from the conveyor line, requiring the tank’s receiving table to be level with the production line and its dimensions suitable for the available space on the production floor.

The ACS engineers opted for a hydraulic system with a manual pump and dump valve, allowing remote battery submersion and raising while ensuring personnel safety.

Additionally, the tanks were crafted for mobility, featuring industrial casters securely fastened to the floor to ensure stability in the event of seismic activity, given the manufacturing facility’s location in a seismically active area.

The Outcome

The aerospace company has two dunk tanks engineered to be a highly effective solution to contain thermal events for the lithium ion batteries it produces. The tanks also meet the aerospace company’s requirements to be mobile and operational without electrical power.

The ACS engineering and manufacturing teams, known for their expertise in welding sealed vessels, collaborated closely on the project. Together, they designed and fabricated the dunk tanks with minimal welds and joints reducing the likelihood of leaks and ensuring long-term durability.

Before deployment, the ACS team rigorously conducted leak checks and functional testing on the tanks in the ACS manufacturing facility, ensuring their operational reliability and readiness for use. Customized to fit the company’s lithium ion batteries, these tanks offer both cost-effectiveness and alignment with the aerospace manufacturer’s requirements.

Key Features

  • Designed lithium ion battery aircraft testing dunk tanks measuring 70” x 93” x 43”, capable of holding batteries weighing up to 500 pounds.
  • Tanks capable of safely dissipating 75.4 kWh of energy during a thermal runaway battery event without raising the water temperature above 140°F.
  • Hydraulic system enabling safe and controlled battery submersion.

ACS Services

  • Completed heat transfer analysis, ensuring the tank’s ability for safe containment and thermal energy dissipation.
  • Designed and fabricated two lithium ion battery aircraft testing dunk tanks that can safely submerge a failing aircraft battery.
  • Conducted factory acceptance testing.