Electric vehicles and storage systems: Critical challenges facing the fire service
Why do these systems catch on fire and how do we manage it?
You get called out to an interstate accident with a vehicle on fire. You arrive on scene to find the vehicle fully involved.
During your 360, you identify that the vehicle is a Tesla, and you quickly start trying to formulate a game plan. Here’s the problem: What you’ve seen in the media and most training guidelines advises you to have access to tens of thousands of gallons of water, and your “Spidey-senses” are telling you the vehicle is a small substation that could electrocute your entire crew. It’s going to block traffic forever, and you’re going to be standing in front of the TV cameras in three hours when this thing is still a raging inferno.
Let’s take this opportunity to address the real-world information you need to know about these systems and how to handle them. We’ll focus primarily on the fire side of this topic. Why do these systems catch on fire and how do we manage it? The energy concerns are another topic that we will discuss in a follow-up article.
Years of personal energy experience
Let’s first start by qualifying my perspective. I lead a group that is part of a collaborative energy safety team. Over the last decade, we have destructively tested more large-scale lithium-ion battery systems than anyone in the world. Some of our testing is certification-based, and some of it is purely research-based. But every test involves suppression, ventilation, gas analysis, and comprehensive battery assessment. We also conduct in-depth forensics analysis post-test.
We have tested everything from vehicle batteries to full containerized rack systems, including maritime batteries for oceanic vessels. We crush them, puncture them, expose them to external fire, overcharge them and overheat them. We even do ballistic testing and shoot them.
If there is anything to learn from these battery systems, we attempt to learn it. Much of what we do is highly sensitive and non-disclosable; however, the findings can be characterized and communicated without compromising specific information about specific clients. What we’ll cover here is based on my personal experience damaging, suppressing and extinguishing hundreds of systems that are all different, yet respond with predictable results to common practices.
A significant – and growing – problem
Now, let’s justify the significance of this problem. Electric vehicles (EVs) and fixed electric storage systems are advancing in the market at an obscene rate. We will be hard-pressed to find a standard combustion vehicle on the roadway in 10 years, and residential and commercial buildings as well as utility installations and manufacturing plants are already converting to battery storage systems.
If you haven’t dealt with one of these systems yet, you will – soon. To understand the challenges you are going to face, we must first understand what the systems do and what problems can arise.
EVs and storage systems: How they work
The high-voltage batteries that are present in EVs are basically the same as the high-voltage vehicles in the fixed systems. Imagine a shipping container that is full of boxes with a bunch of small trinkets in the boxes. That is your battery system. It’s either a rack or a container that has smaller containers in it that are comprised of even smaller batteries. The batteries can be pouches or prismatics. This means they are either flat metallic envelopes or they are cylinders that don’t look very different from your standard AA batteries.
These batteries receive energy from a source. For fixed sites, it can be solar panels or wind turbines, or it can be direct feed from the grid. These batteries can both collect and distribute energy and convert it to usable AC or DC. Vehicles that are hybrids will additionally have regenerative braking applications that will create energy and send it to the high-voltage batteries for storage. Plug-in vehicles are charging the high-voltage batteries through a charging station, which is pulling energy from the grid.
In either case, it is important to understand that you are dealing with both AC and DC with these systems. AC will be in play for your low-voltage systems that power your creature comforts and safety systems or control systems.
The high-voltage system will be used for the electric motors that power the vehicles or the buildings. It is not advisable to attempt to interact with the high-voltage systems without proper training and equipment. You will almost always have stranded energy in these systems that creates the potential for electric shock and arc/flash hazards. We have conducted dismantling operations post-fire incident where piles of molten plastic produced arcs up to two feet when a hand tool was in proximity.
Dealing with batteries
There are a few primary things that batteries don’t like – electrical damage, excessive heat or mechanical damage:
- Electrical damage can be caused by shorts or improper energy coming to the battery or leaving the battery.
- Excessive heat can occur internally when cooling mechanisms fail or externally through extreme environmental conditions or external fire exposure.
- Mechanical damage occurs when the batteries are traumatized or physically damaged.
In all three of these, the responsive process is the same; it just varies in significance and speed. Let’s break that down.
When the batteries have undesirable conditions – electrically, mechanically or thermally – they begin to heat and swell and off-gas. The off-gas is comprised of full-blown hazmat stuff – VOCs, carbon monoxide (CO), hydrogen, etc.
The gas that you can realistically interpret in the field is CO. Once the batteries build up enough pressure, they rupture, spewing pressurized gas that, when combined with heat and the right air mixture, ignite. One battery affects the next battery, which affects the next battery, and so on until you develop “thermal runaway.” This is now a situation where the batteries are cascading through one another, building heat chemically and thermally and producing their own oxygen to support combustion – all the while arcing, sparking and posing significant electrical hazards.
Sounds pretty terrifying.
Even worse, the speed factor that I mentioned can create very difficult scenarios for first responders, tow and recovery specialists, and site managers. If the exposure to one of the damaging elements is sudden and volatile, then the reaction typically mimics that. In other words, a vehicle that runs head on into a semi-tractor at 120 mph has the potential to have a very rapid and violent progression into thermal runaway. Conversely, a moderately damaged vehicle that has compressed the high-voltage casing and caused two small batteries to start overheating may have a very delayed reaction. This vehicle may not reveal thermal runaway for days or weeks after it has been sitting in the salvage yard.
How firefighters should handle energy systems
Now that we have laid the foundation for the problem and the general science and characteristics behind these systems, lets get to the good stuff. How do we handle them?
First and foremost, SEEK EXPERT GUIDANCE! There are new federal standards available from NFPA, NTSB, NHTSA and SAE that promote safe interaction and handling of these systems and events. Compliance with these standards is paramount to the safety of your crews and the communities you serve.
There are two outstanding resources available to help you comply with the standards and safely operate: The Energy Security Agency and the Energy Safety Response Group.
- The ESA (855-ESA-SAFE) is a 24/7 call center that provides free consultation to responders dealing with vehicle based electric and hybrid/electric vehicles. They also provide training and resources for interacting with these vehicles. Once you are on scene, hopefully you have the ESA on the phone to help you.
- ESRG is a more hands on group designed to assist with large-scale fixed site emergency management, training, site design and safety planning.
Be as prepared as possible and seek help from these two agencies.
Now, let’s turn to some keys to operations.
Identification: The electrolyte compounds in these batteries emit a unique odor when overheating and off-gassing are imminent. Tesla describes it as “cherry bubblegum.” It is a sweet aroma. If you detect that odor on scene, assume the batteries are going to be a problem.
Use your thermal imagery capabilities to scan the battery systems. The systems will have a heat signature that should be uniform. If you detect any specific hot spots within the system, that can be a strong indicator of a battery problem. Other, more obvious identifiers include smoke, heat and fire.
If you have a battery-based fire, remember that what has ignited is a pressurized stream of gas. It will find the path of least resistance and make that path bigger. The gas streams will ebb and flow with each battery cell as it “pops off.” This is the part of the scenario that can take hours, and as it progresses, it is going to involve other fuel loads in the vehicles, such as the tires, carpet and upholstery, etc.
Until the other fuel loads are involved, the smoke signature can be very misleading. This is particularly true with fixed site systems. If the batteries alone are burning, the smoke may remain very white or light gray and will not have a heavy carbon footprint. We have experienced a multitude of flashovers and smoke explosions with smoke conditions that did not meet any of the traditional patterns of dark pressurized smoke. That Is because the chemical makeup of this smoke is unique and highly flammable, without the typical presence of the heavy carbon loads we see in structure fires. If you detect any specific hot spots within the system, that can be a strong indicator of a battery problem.
If you have victims in the vehicle, work fast to rapidly extricate and get lines on the ground. If there is no fire, but smoke is present, rely on your CO monitor to help clue you in to the presence of battery involvement. Even lazy and light smoke that might appear to be airbag smoke could be the onset of battery failure. Err on the side of caution, and use the smell test, TIC test and monitor test to clear the hazards.
Let it burn: Here is where it gets controversial: If it is on fire, your absolute best option is to protect exposures and let it burn. Unless you have a life safety issue or some other significant reason to try to shorten the time span, LET IT BURN. The vehicle will be safest when it is “comfortably burning.”
The burning process is consuming all the hazardous gasses, not allowing them to build up and combust. When we disrupt the burning process, especially with extinguishing agents that interfere with oxygen interaction more than they cool, we simply put a short-term band aid on the situation and allow it to continue to cascade through thermal runaway while off-gassing unignited vapors until we have the right ignition temperature and air ratios and we explode. I have personally witnessed this countless times with suppression agents.
If you have to aggressively attack this fire, do not buy into the surround-and-drown model of extinguishment. Part of our responsibility is to protect and conserve property. The runoff from these fires can produce water that is very basic and result in extremely costly EPA cleanups of the resulting contaminated swamps.
As such, focus fire attack on the battery itself. You can identify the battery location through your interaction with the ESA. Find the most evident vent point coming from the battery. This will be your most prolific “blow torch.” Knock the fire down from a safe distance, then advance on the vehicle and apply a controlled stream through the vent point. The goal is to apply isolated flooding and cooling to the batteries themselves.
Remember our initial analogy of a container filled with boxes filled with trinkets. If you don’t get water to the trinkets, you aren’t accomplishing anything other than flowing ineffective water. I equate the surround-and-drown concept to setting up the aerial and flowing water on the roof of a four-story structure with a basement fire. I’m sure the fire will eventually go out, but it will most likely not be because of our water application.
You also don’t need big lines for this. You need mobile lines that you can flow at quarter bale, directing controlled streams very surgically into the openings that will allow water to get to the batteries.
I have put out hundreds of these fires using the essential approaches I described above, all under the watchful eyes of the engineers and designers that make the systems. The guidance I have shared with you today is based on real-world safety and science.
Don’t hesitate to reach out to me for additional training or questions. Stay safe and train hard!!