With the increasing use of electric bikes and scooters, it is important to understand the risk of lithium-ion battery fires. While e-bikes and e-scooters have revolutionized personal mobility, offering a sustainable and efficient alternative to traditional transportation methods, their popularity has brought to light incidents involving battery fires. Fortunately, following best practices and undertaking preventative measures can nearly eliminate the chance of a battery fire.

Lithium-ion batteries are the most common choice for e-bikes and e-scooters due to their high energy density, lightweight construction, and relatively long cycle life.[1]  However, battery quality is an important factor regarding fire risk. Generally, good batteries aren’t cheap, and cheap batteries aren’t good. Owning and riding micromobility devices can be perfectly safe if you buy a device with a battery that complies with product standards and follow the manufacturer’s instructions.

Primary Causes of Lithium-Ion Battery Fires

The primary causes of lithium-ion battery fires are the use of low-quality batteries and chargers and improper battery charging.

Low-Quality Batteries

A lack of mandatory federal safety standards regarding battery and e-bike production, combined with the recent surge in popularity of e-bikes, has resulted in the proliferation of low-cost, often low-quality batteries and devices. Low-quality batteries can pose risks because they often lack certain safety systems crucial to preventing overheating and overcharging, which can lead to fires. Most high-end electric bikes have a Battery Management System (BMS) to prevent battery overcharging or overdraining. Lower-quality batteries may lack a BMS, increasing risks of overcharging and overheating. In addition, low-quality batteries often have poor heat management or inadequate venting systems, making them more susceptible to fire.

Improper Charging

Improper charging of low-quality batteries, such as overcharging or leaving recharging batteries unattended overnight, can cause them to overheat. This can make the batteries explode, causing a fast-moving fire that is difficult to extinguish. Using mismatched chargers and batteries can also result in overheating and lead to fires.

Other Causes

Other less common causes of fires include improper battery storage, battery tampering, prolonged use and improper cooling, battery deterioration over time, and poor battery maintenance.

Preventing Lithium-Ion Battery Fires

Tips for Consumers

In general, consumers should choose an e-bike or e-scooter that uses high-quality batteries from reliable manufacturers who follow safety regulations and meet industry standards. You should always look for positive customer reviews on reputable platforms and websites. To ensure a quality purchase, you should look for products with certain safety certifications and features. You should also practice safe charging, storage, and disposal methods.

Safety Certifications and Features

Underwriters Laboratories LLC (UL) is a global science safety organization that conducts testing, inspection, and certification services for a range of products. A UL certification indicates that a product has met a certain safety standard. Consumers should check products for appropriate UL safety certifications:

  • “UL2271” for lithium-ion batteries in light electric vehicles (LEVs)
  • “UL2849” for e-bikes and electrically power-assisted cycles (EPACs)
  • “UL2272” for personal e-mobility devices, including e-scooters, e-skateboards, and hoverboards.

It is also important to look for products that incorporate the following safety features:

  • A Battery Management System (BMS) to monitor voltage, current, temperature, and state of charge.
  • Thermal Management Technologies such as cooling fans, thermal pads, or heat sinks to disperse heat and prevent thermal runaway, a condition that occurs due to battery defects or charger issues, in which damage to one battery cell can cause nearby cells to overheat. Thermal runaway events can also produce toxic gases that endanger people and property.
  • Fault Tolerance to lessen the effects of component failures and avert catastrophic fires.

Before making a purchase, you should look for robust warranties and accessible customer support channels. You should also always research the reputation of manufacturers before buying a product and explore relevant online forums to look for first-hand consumer experiences and recommendations.

After a lithium-ion battery fire is extinguished, firefighters place the battery in a 55-gallon drum filled with CellBlockEX to prevent reignition. The above photos were taken in a firehouse. (Stephen Dunn)

Safe Charging

Only use chargers authorized by the battery’s manufacturer and always follow instructions to avoid overcharging. You should avoid incompatible chargers, always charge batteries away from flammable materials, and ensure that batteries are physically separated to prevent thermal runaway.[2] Never charge a battery overnight, and do not leave charging batteries unattended, as this often leads to overheating. To help with this, you can use an outlet timer or set a manual timer as a reminder to disconnect a device when it is finished charging.  Always remove the battery if the device is not going to be used for 12 or more hours. This allows the battery to cool and decreases the risk of overheating and thermal runaway.

You should also avoid charging in parking garages or apartment entryways and avoid charging damaged batteries or batteries that have been submerged in water. Only connect chargers directly to wall outlets. Do not use power strips or extension cords. Be aware that battery tampering, such as refurbishing or reassembling batteries incorrectly, can also increase fire risk.

Safe Storage, Maintenance, and Disposal

When storing your micromobility device, you should always opt for cool, dry conditions, away from combustible objects or direct sunlight. For devices being stored indoors, seek options that are fireproof and well-ventilated.

It is also important to regularly inspect devices and batteries for wear and damage. Clean battery terminals and check for corrosion and wear on a regular basis. If problems arise, contact the manufacturer or a specialist. Remember that lithium-ion batteries deteriorate over time, which can increase their risk of overheating.

You should always remember to dispose of damaged batteries safely at a municipal household hazardous waste drop-off center. When making other decisions regarding a potentially damaged lithium-ion battery, always consult a professional before taking action.

Tips for Property Owners and Managers

Property owners and managers may benefit from providing a safe, separate location for micromobility battery charging and storage, ideally away from residences. Properties that lack space for separate infrastructure can designate a safe space outdoors where, if a fire erupts, it can be properly contained, reducing risk to residents.

When providing a separate charging and storage space, consider the following:

  • Use or enforce the use of high-quality, approved chargers made specifically for e-bike and e-scooter batteries.
  • Designate fireproof storage locations constructed using fire- and blast-resistant materials.
  • Install fire and smoke detection systems to reduce the likelihood of fires spreading undetected.
  • Ensure proper ventilation in charging and storage infrastructure.
  • Install self-closing doors to prevent fires from spreading.
Remember: If a fire does start, leave the building immediately, closing doors behind you to prevent the fire from spreading. Once you are safely out of the building and away from the fire, call 911. 

[1] Cycle life refers to the number of complete charge and discharge cycles a battery can support before losing performance.

[2] Thermal runaway is a condition in which damage to one lithium-ion battery cell can cause the overheating of nearby cells. The phenomenon is triggered by battery defects or issues with chargers, causing an uncontrollable release of stored energy, which can result in an explosion or fire. Because the battery system fails gradually, the fire produces a lot of heat over time, which can be dangerous, especially in residential settings. Thermal runaway events can also produce toxic gases which endanger people and property.

Sources

Dragonfly Energy. What Is A Battery Life Cycle? https://dragonflyenergy.com/battery-life-cycle/

Hindson, B. Battery safety vital for maintaining confidence in micromobility.  https://zagdaily.com/opinion/battery-safety-vital-for-maintaining-confidence-in-micromobility/

Juiced Bikes. How to Avoid E-Bike Battery Fires: 5 Safety Tips. https://www.juicedbikes.com/blogs/news/how-to-avoid-electric-bike-battery-fires

Kanter, E. How to Safely Charge and Store E-Bike Batteries. https://ev.aaa.com/articles/e-bike-batteries/?cmpid=int_eml_out_exx-0723-ev-nwslttr&cid=DM452743&bid=623642383&hme=a4fc7745a8c0b194a737ac0abf88832d5c7397952dc45b51f2b5c7b0a393cf49&emid=int_eml_out_gen-cont&segment=6202407032706228

Salmonsen, Mary. How to safely store e-bikes, e-scooters in apartments. https://www.smartcitiesdive.com/news/how-to-safely-store-e-bikes-e-scooters-on-multifamily-fire-safety-lithium-ion/689861/