Worried About E-Vehicle Battery Fires?

Fires from lithium-ion batteries are frightening, but research confirms that proper charging and fire protocols reduce the risks and save lives.

You’ve probably seen headlines about electric scooters “exploding” and EVs burning down a home from a fire started in the garage. Before I jump into some research about how to reduce the life and property risks from such events, let’s tone down the panic level a bit.

Image Credit: FRSI

All Vehicles Pose Fire Risks

When EV fires do start, they tend to grab headlines. Who doesn’t want to read about an expensive Tesla going up in flames? But the reality is that gasoline-powered engines catch on fire way more often than their lithium-ion battery-powered alternatives. 

As MotorTrend.com reports, “the data shows that EVs account for a tiny fraction of car fires each year.” They found that more than 98 percent of fires involving vehicles started with liquid fuel engines.

Another study by AutoInsuranceEZ in 2021 found that petrol and diesel vehicles experienced 1,530 fires per 100,000 vehicles, while only 25 out of 100,000 fully electric vehicles caught fire. By this logic, that old pickup truck in your garage may be 61 times more likely to be involved in a vehicle fire than your brand new Ford F-150 Lightning (An EV vehicle).

It’s important to keep this risk disparity in mind when talking about battery fires. Electric vehicles, when charged properly, pose a much lower safety risk than fossil fuel-powered equivalents, but they get a lot more media coverage. And EVs are hands-down the greener choice. Unlike their gas-powered predecessors, EVs can be charged with renewable energy. 

With the understanding that battery fires are rare, let’s take a look at what causes them, along with how to make them less deadly.

Battery Explosions: Attention-Getting Events

When EV, scooter, or e-bike batteries do catch fire, they tend to do so with spectacular results. The batteries, typically made with lithium, explode, sending chunks of burning material into different parts of a room.

This video demonstrates what happens when e-scooters are overcharged to the point of explosion. Note that these were intentional mis-charges to examine how battery fires spread.

As the number of e-bikes and e-scooters rises rapidly, so, naturally, do the number of fires. The NFPA reports, for example, noted a 50 percent increase in e-bike or e-scooter fires in New York City from 2021 to 2022. The number jumped to about 160 incidents, versus 104 the previous year.

That’s not necessarily an “epidemic,” as you might infer from news coverage of these fires, but it’s a scary scenario, and one that needs to be addressed quickly. As an article from Techcrunch succinctly explains, to reduce the risk of lithium-ion battery fires, we first need to understand why they happen: 

“There’s a chemical and a practical answer to this question. The chemical answer is that lithium-ion cells undergo a process called thermal runaway, which results in a sharp increase of battery cell temperature and pressure, accompanied by the release of flammable gas. The flammable gas can ignite from the battery’s high temperature, resulting in a quick fire that’s hard to put out and emits toxic fumes.”

The first line of defense against e-fires, according to post-mortem studies, is proper battery charging. Before we talk about how to put out one of these fires, here’s a basic charging and storage safety checklist:

• Use OEM or Certified Chargers: Stick to the manufacturer's charger or certified alternatives.
• Match Charger Specs: Ensure the charger's amperage and voltage align with the battery's specifications.
• Monitor Battery Health: Regularly check for wear or damage; replace old or deteriorated batteries.
• Charge in Moderate Temperatures: Avoid charging in extreme heat or cold.
• Safe Charging Location: Charge in well-ventilated areas, away from flammable materials, ideally in a space isolated from living areas.
• Unplug Fully Charged Batteries: Disconnect the charger once the battery is fully charged, or make sure your BMS does this.
• Use a Battery Management System: Ensure your device has a BMS to prevent overcharging.

These steps should greatly reduce any fire risk. But let’s assume the worst happens. How do you reduce property damage (and survive) a lithium-ion battery fire in your home?

Will Sprinklers Suppress a Battery Fire?

Research from the Fire Safety Research Institute looked at e-scooter and e-bike fires in controlled settings. 

At issue is the question of storing these products in homes. What’s the best location in which to store them? What happens in the rare instance that they are overcharged and explode? Will sprinkler systems help?

Mismanagement of battery charging has a cumulative effect on risk of fires. Source: FSRI

Last spring, FSRI conducted a series of tests (shown in the video above) to assess whether home sprinklers can control an e-vehicle fire. They intentionally overcharged the e-vehicles to the point where the batteries exploded. The fires spread rapidly, with an accelerated point of “flashover,” considered the most tipping point in a home fire.

The result was dramatic, as expected, but the good news is that the sprinkler systems did their job, which is to slow or prevent flashover, even in the extreme situation of an e-battery fire. As the report notes:

“The goal of a residential sprinkler system is to prevent flashover by limiting fire growth.

Throughout the series of experiments, FSRI consistently observed that while the room of origin was damaged, sprinklers did not allow flame spread to secondary items, and ultimately prevented flashover.”

Battery fires release a lot of toxins, and FSRI notes that they’re conducting more detailed analysis of total toxins released into the test rooms. Initial results suggest, however, that the sprinklers in enclosed rooms would have saved lives, by keeping toxin levels at a low enough level for occupants to escape and firefighters to arrive on the scene.

The National Fire Protection Association is actively working to educate e-bike and e-scooter owners about safety protocols. You can review their free tip sheet, plus other educational and outreach tools.