A disruptive technology poses fire safety risks for consumers and firefighters
Energy Fires ❘ By Chris Greene
Lithium-ion batteries are a true disruptive technology on a multitude of fronts. In the portable technology global landscape, if you are not producing a product that can use lithium-ion batteries, you are dying on the consumer vine. It is getting nearly impossible to find a rechargeable handheld device that does not run on lithium-ion batteries. For consumers, the decision to power up with these batteries is long over, and we love it. We have more product choices than we’ve ever had. These devices are more powerful, are more versatile, and last longer on a single charge than we ever thought possible. As the world is in a race for alternative energy that is not a part of a grid that depends mostly on coal and other fossil fuels, here come lithium-ion battery systems that can be paired with solar/wind/wave energy creation systems to form “The Micro-Grid.” The great thing about this technology is there is absolutely zero downside—“guilt-free” energy creation, containment, and distribution—well, almost. When the batteries heat up; overcharge; get bumped too hard; or just don’t agree with the cheap, new, albeit knockoff charging device you bought online, they are catching fire.
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Battery Cell Types
To understand lithium-ion batteries, let’s start with the basics, the battery cells. The three most common cell designs for lithium-ion energy are as follows:
Lithium-ion polymer/pouch cell (photo 1). This is the most common type produced. It is found in electric vehicles (EVs), cell phones, and everything in between. The only real difference is in the dimensions of this battery and the number of them used in each device. For example, there may be 350 pouch cells used to make up the battery for an EV and only one small pouch required to power up your cell phone. The pouches will differ in size, but the voltage of each cell is consistently between 3.2v and 4.2v. For EVs, cell phones, tablets, and computer manufacturers, this is the most commonly used cell.
Lithium-ion cylindrical cell (photo 2). Sometimes referred to as a “Jelly Roll” by those attempting to describe how the cell looks on the inside, this is the cell type we are most familiar with from a fire perspective. It is the work horse of the micro-mobility “E-bike” industry and is responsible for more sleepless nights for the fire service than we can count. This cell is found in everything from E-bikes to flashlights to cordless “everything” tools. Over the past few years, E-bikes and cordless tool battery failures have become a common culprit of fires. This is a new phenomenon that we did not experience to this scale 20 years ago and can be tied directly to the proliferation of lithium-ion battery devices. Many fire investigators have learned that they need to rule out battery failure as a cause of fire similar to electrical, as they are both common fire causes absent an external flame source.
(1) Lithium-ion polymer/pouch cell. (Photos by author.)
(2) Lithium-ion cylindrical cell.
(3) Fire damaged lithium-ion prismatic cell.
Lithium-ion prismatic cell (photo 3). This is the least common of the three; it is a prefab of sorts, made up of pouch cells wired together and housed in a rigid casing. These casings are often stacked together to make up a prismatic battery module. They are found in EVs, uninterrupted power supply (UPS) rooms, and battery energy storage systems (BESS). Because of their larger size, they are not well suited for handheld devices and micro-mobilities.
What They Are and Are Not
Lithium batteries are primary/nonrechargeable batteries. They have a lithium metal anode and are noted for their high energy density when compared to other primary battery formats—i.e., alkaline batteries. They are commonly used in portable battery-operated devices and most notably used in “maintenance-free” smoke detectors and pacemakers. When shipped in bulk, they should be labeled UN 3090/91. Lithium metal will react violently when in contact with water; suppression considerations should include use of class D extinguishment mediums. An unfortunate side note: The lithium metal anode “strip” is commonly harvested and used in the illicit meth manufacturing process.
Lithium-ion batteries are secondary/rechargeable batteries. There is very little lithium used in their production. The lithium used is minute, like dust, and is located in the electrolyte solution of the battery. The electrolyte is a proprietary suspension agent for the lithium particles. This electrolyte is extremely flammable, on par with gasoline. This is one of the reasons a failure of these cells can be unusually problematic. Unlike the lithium metal battery, water is the preferred suppression medium for fires involving lithium-ion batteries in any format. The fact is, there is simply not enough pure lithium metal in a lithium-ion battery to warrant use of anything other than water. When shipped in bulk, they should be labeled UN 3480/81.
Truths About Any Lithium-Ion Cell
Lithium-ion fires are going to be challenging. They burn without oxygen, and they can burn underwater. Once the process of thermal runaway begins, it is nearly impossible to stop in that particular cell. The failure process for a cell can take seconds or several weeks, leaving you to wonder when an incident involving them is stable and safe to leave.
When a cell fails, it will vent an electrolyte gas and often a fire stream up to three feet in length. Hydrogen gas is one of the most common gases vented from the cell, and the hazard profile is directly tied to location. Cooling adjacent cells and the surrounding casing will be the only chance to keep this cell fire from propagating to the next cell, which is when we really get into trouble.
The upside is that these basic concepts are consistent across the board. The only differences will be the number and location of the cells. An E-bike fire in the street has a completely different hazard profile when compared to a BESS inside a building. For BESS facilities, you should assume a defensive posture right out of the gate.
Energy emergencies are the new “hazmat/technical rescue” tool heavy discipline. Exercise prudence and caution when working with vendors trying to sell you their newest must-have widget-tool for tackling fires that involve lithium-ion batteries. If you are involved in purchasing/procurement for your agency, take the time to understand how lithium-ion batteries work and how they will affect the fire service landscape.
Future articles will be more specific on how lithium-ion batteries will affect your operations. Understanding and combating this energy hazard is going to take some time. However, the challenges we are facing are unlike anything we have seen in the past, certainly the scale of this hazard. We will offer specific tactics on addressing this hazard but, ultimately, you will need the tools to recognize the lithium-ion influence if you are to have operational success. You are going to see fires in homes, apartments, freeways, buildings, transport ships, and airplanes—all with nexus to lithium-ion cells. Welcome to the world of energy emergencies.
Chris Greene is a captain in the Seattle (WA) Fire Department with 29 years of service. He is the supervisor in charge of the department’s Energy Response Team, which operates out of Fire Station #25 on Capitol Hill.
