BACKGROUND

The risk of lithium-ion battery fires is a concern for transit agencies that are considering whether to electrify their bus fleets. The transit industry has largely addressed lithium-ion battery fire risk by incorporating rigorous early detection and protection protocols in battery management systems that prevent thermal runaway when the battery pack is physically compromised through improper use or external impact. At current zero-emission bus (ZEB) fleet scales, the magnitude of these risks is relatively small; there is, however, no widespread understanding of how lithium-ion battery fire risks will be magnified when fleet size increases. Damaged cells in a lithium-ion battery can lead to thermal runaway, a phenomenon in which a failure in the architecture of a battery cell (e.g., a short) causes the heat of the battery to rapidly increase, releasing flammable gas which then ignites, triggering similar events in adjacent cells. The ensuing fires are difficult to extinguish and must be addressed with significant quantities of specialized fire suppressants. There are also documented instances of stranded energy remaining after a lithium-ion battery fire is extinguished, causing batteries to reignite after the fires have been initially suppressed by first responders.

Transit organizations seek answers to questions that will inform their planning, procurement, operations, and maintenance practices, such as:

• What are the best practices for extinguishing a lithium-ion battery fire?
• How can fire and life safety experts help with prevention and mitigation during the planning and implementation of battery management systems?
• Colocating fleets with differing energy/fuel systems is a complex risk situation. What is the quarantine or isolation procedure to avoid parking a vehicle of concern in proximity to other assets?
• How can agencies be confident new vehicles can be safely parked in legacy facilities?
• What are the concerns for battery-electric buses and hydrogen fuel cell buses? What fire suppression technologies are applicable?
• Is there a threshold of degradation that indicates a bus is risky to charge and operate? How can an agency test and monitor battery degradation across their transit fleet?
• What are indoor and outdoor sequestration approaches?
• What technologies are available for polling or monitoring lithium-ion battery systems?
• What is the best way to illustrate the operational life cycle of a ZEB?
• How might agencies determine the key performance indicators (KPIs) that can be measured and monitored to ensure lithium-ion battery health and safety?
• Small operations are not staffed 24 hours a day. Thermal alarms and chargers should be shut down if high temperatures are reached. What are best practices for lithium-ion battery management and notification? For battery safety monitoring?
• In a lithium-ion battery fire, gases are generated; depending on the type of structure the vehicles are housed in, staff (including first responders) will be exposed to gases. How can an agency manage that gas release and mitigate the health risks to workers?
• How can an agency interrogate a battery for problems? What should such a device do? How can such a dataset be shared or used to determine overall industry compliance? To ensure that data on vehicle/battery performance are publicly available?
• Should agencies include stress tests on barriers to fire spreading in requests for proposals (RFPs) prior to receiving lithium-ion battery systems? What national and international standards apply? What are industry practices?
• How would transit agencies deal with an original equipment manufacturer (OEM) recall?

OBJECTIVE

The objective of this research is to develop a guide to lithium-ion battery transit bus fire prevention and risk management with recommended practices for original equipment manufacturers, battery companies, transit agency facilities, and vehicle maintenance.

The focus should be on zero-emission transit bus fire prevention and risk management. A parallel project is addressing power generation, distribution, and charging infrastructure; institutional relations; and operations.

At a minimum, the research team shall (1) review the potential root causes of ZEB lithium-ion battery fires, including an analysis of the potential of such fires to spread to other vehicles or reignite after suppression; (2) evaluate risk mitigation options; (3) identify, evaluate, and summarize effective practices for fire risk mitigation and suppression, focusing on agencies that store and charge their buses in indoor facilities; (4) identify quantitative and qualitative metrics that can be used to evaluate vehicle and battery performance as they relate to fire and life safety; and (5) address the technical, economic, and institutional barriers to implementing identified solutions.

RESEARCH PLAN

The research plan will describe appropriate deliverables that include the following (which also represent key project milestones):

1. An Amplified Research Plan that responds to comments provided by the project panel at the contractor selection meeting.
2. An Interim Report and panel meeting. The Interim Report should include the analyses and results of completed tasks, an update on the remaining tasks, and a detailed outline of the final research product(s). The panel meeting will take place after the panel review of the Interim Report. The Interim Report and panel meeting should occur after the expenditure of no more than 40 percent of the project budget.

FINAL DELIVERABLES

The final deliverables will include:

• A guide to lithium-ion battery transit bus fire prevention and risk management.
• A stand-alone technical memorandum titled “Implementation of Research Findings and Products”.
• A report with the following:
  • Documentation of the research activities;
  • Key findings; and
  • Other topics identified during the project.

STATUS: A research agency has been selected for the project. Research in progress.