To extinguish a burning e-bike battery

Electric bikes and pedelecs have become increasingly popular in recent years. Not only among seniors, but also among commuters, recreational cyclists and even competitive athletes are discovering battery-powered bicycles more and more for themselves. For a reasonable range and powerful support, e-bikes and pedelecs are equipped with increasingly large lithium-ion batteries, which often have capacities of 500 Wh and more. This relatively large amount of energy can pose a real danger in a (fortunately very rare) fire incident. Therefore, it is all the more important to have suitable extinguishing agents and battery fire extinguishers ready for use in case of such events, so that the battery fire can be extinguished as quickly as possible. 

The most important things about burning e-bike batteries in brief

A defective battery, incorrect storage, unsuitable chargers – these are the most common causes of an e-bike battery catching fire. If a fire has already started, lithium-ion batteries are difficult to extinguish; special extinguishers for batteries or small fire blankets can be a first measure, but professional firefighting assistance is usually unavoidable. Prevention is therefore especially important: E-bike batteries should ideally be stored in specially designed, fireproof battery bags or boxes for e-bike batteries, as these provide good protection against the spread of a fire caused by the Li-ion battery, even with problematic batteries.

Detailed information on the most important questions about the causes of bike fires, extinguishing e-bike batteries and effective prevention of such problems:

• How can an e-bike battery fire start?
• How high is the fire hazard with an e-bike battery?
• How do you extinguish an e-bike battery fire?
• What are the best measures to prevent an e-bike battery fire?

When can an e-bike battery fire occur?

Modern e-bike batteries are equipped with sophisticated battery management systems designed to prevent overheating or even an e-bike battery fire at an early stage. Nevertheless, it is never excluded that a battery of an e-bike or pedelec can catch fire, either due to a defect in the battery management system or if unsuitable chargers are used. The most common cause, however, is a mechanical defect, which can have many causes for e-bike batteries and can, for example, lead to a short circuit. Because of the potential danger, it is generally recommended to store them safely when not in use, regardless of the condition of the e-bike battery. Suitable boxes for e-bike batteries depend on the battery size, for example the Zarges K470 Akku-Safe, the B&W Akku-Koffer, or the various boxes of the Genius Lio-Guard series. Also suitable are battery bags made of fireproof material.

Defective battery due to a mechanical impact

In principle, e-bike batteries are relatively robust energy storage devices. Nevertheless, strong mechanical stresses inside the battery cells can cause damage. Typical scenarios are accidents involving the e-bike or when the battery falls to the ground. Externally, the batteries are often still completely intact and they still provide energy for cycling as usual. If you then reconnect them to the charger, defective batteries can cause problems and even lead to a fire of the e-bike battery. But even when not charging, a so-called thermal runaway can occur—a chain reaction in which battery cells overheat and cause a fire, and in the worst case the e-bike battery can even explode. 

How high is the fire hazard with an e-bike battery?

The good news first: The fire hazard with an e-bike battery is very low when stored and used correctly. This is also supported by the fact that one hardly ever hears of an e-bike fire, although the prevalence of e-bikes has increased significantly in recent years. Accordingly, you should not refrain from buying a pedelec or e-bike because of the fire hazard of an e-bike battery, but rather consider the appropriate measures to store the e-bike battery correctly and thus minimize the risk of a battery fire.

The fire hazard increases with defective e-bike batteries

While intact and correctly used batteries for e-bikes and pedelecs are very safe, the fire hazard increases sharply with defective batteries. Obviously defective e-bike batteries should not be used anymore, but replaced with a new battery. The defective battery must be disposed of properly, otherwise there remains a higher fire hazard. And even if, for example after a fall, the battery appears externally to be in good condition, internal damage to the delicate separator layer may have occurred, which also increases the risk of an e-bike fire. Therefore, appropriate caution and adherence to the necessary safety measures when storing and charging e-bikes apply.

How do you extinguish an e-bike battery fire?

If an e-bike battery catches fire, the classic ABC or carbon dioxide extinguishers are generally not the first choice. Normal water extinguishers are also not very suitable, as further short circuits can occur in an electrical system. Special extinguishers for lithium batteries are the better choice: extinguishers filled with silica, gel or Pyrobubbles, for example, provide an efficient way to extinguish the burning e-bike battery. But here too: preventive measures to prevent a bicycle battery from catching fire in the first place, or preventing the battery fire from causing greater damage, are always better than active firefighting. Accordingly, the correct storage of e-bike batteries is crucial. Even seemingly small e-bike batteries can cause major problems when extinguished.

Important first steps for extinguishing a burning e-bike battery

1. Protect yourself: First ensure your own safety and the safety of those nearby. Keep a sufficient distance from the burning battery and avoid inhaling smoke and fumes, as they can be toxic.

2. Cut off the power supply: If possible and safe, disconnect the e-bike from the power source. Switch off the bike and remove the battery if this can be done safely.

3. Use a fire extinguisher or a fire blanket: Use a special fire extinguisher for lithium-ion battery fires, based on the fire classes D or F (in some countries also called class D or K). This type of extinguisher contains an extinguishing agent that is specifically suitable for metal fires, such as dry ice, metal fire powder or extinguishing granules. A conventional ABC fire extinguisher may not be effective enough and could even cause a more intense reaction. Details on suitable battery extinguishers can be found below. Alternatively, a extinguisher for lithium-ion batteries can also be used. 

4. Cool the battery: Once the flames are under control, try to cool the battery with plenty of water or sand. Make sure you do not aim directly at the battery, but apply the water or sand from the side to avoid a steam explosion. Cooling is important to prevent re-ignition of the battery.

5. Call the fire department: If you cannot extinguish the fire yourself or are unsure how to proceed, call the fire department immediately. Inform the responders that it is a lithium-ion battery so that they can take the appropriate extinguishing agents and precautions.

6. Do not leave the battery unattended: Even if the fire is extinguished, the battery may still be at high temperatures and pose a danger. Do not leave the battery unattended and wait until it has cooled completely.

In the following sections, individual extinguishing agents will be explained in more detail, which can be used as part of the initial measures. 

Gel extinguishers for e-bike batteries with Water-Glue as extinguishing agent

Gel extinguishers operate with a gel-like extinguishing agent, which can be used very efficiently for fires of e-bike batteries. In addition to the direct cooling effect of the gel, the high heat capacity of this extinguishing agent ensures that the burning e-bike battery loses heat in the absence of oxygen.
The Gel extinguishers are comparatively inexpensive and therefore suitable for extinguishing e-bike battery fires and are highly recommended especially for owners of e-bikes and pedelecs.

Lithium extinguishers for e-bike batteries

Stronger than the gel extinguishers are the so-called lithium extinguishers, which use Lithium-X as extinguishing agent. The silicon extinguishing agent is a watery dispersion in which natural silicon crystals are kept afloat in a watery solution. When sprayed onto a burning e-bike battery, the water evaporates, the microscopic silicon chips swell and fuse into an opaque barrier. This isolates the e-bike battery fire, the thermal radiation above the barrier immediately drops below 100°C, and a thermal runaway is prevented. The lithium extinguishers are somewhat more expensive and are often used in commercial environments, but can also be used by private individuals to extinguish e-bike batteries.

Pyrobubbles fire extinguishers for e-bike battery fires

In addition to the above, there are extinguishers that use Pyrobubbles as extinguishing agent. The extinguishing granulate developed by Genius is very commonly used in the transport of Li-ion batteries, for example as granules in the battery transport containers. In extinguishers, the extinguishing agent can be sprayed directly onto the burning e-bike battery and exert its extinguishing effect there. Similar to the lithium extinguishers, these are more often found in the commercial sector and are rarely used by private individuals to extinguish an e-bike battery fire. At the same time, one should always keep in mind that extinguishing e-bike batteries with Pyrobubbles requires special fire protection concepts, which usually do not only include Pyrobubbles, but also the tightly closed battery containers. 

Fire blankets for lithium-ion batteries

A further option to effectively combat the fire of an e-bike battery is the use of a suitable fire blanket for Li-ion batteries. In particular the BRIDGEHILL Extreme Fire Blanket fire blanket for small lithium batteries is specifically designed for this purpose and can be especially easily used in the event of a defect or fire of an e-bike battery. But other manufacturers such as Vlitex also offer a comparatively inexpensive model with the fire blanket for battery packs, which can be used to combat a battery fire: simply spread it in front of the problem battery and then throw or place it over the battery. After at least 20 minutes, further measures can and should be initiated to finally extinguish the burning e-bike battery. 

What are the best measures to prevent an e-bike battery fire?

As can be seen in the previous sections, it is sometimes extremely difficult to extinguish an open fire of an e-bike battery. Accordingly, prevention is a recommended strategy to prevent the battery from catching fire in the first place or to prevent a problematic battery from causing damage to the surroundings. Primarily the topic of e-bike battery fire protection is of great importance.

Appropriate storage containers for e-bike batteries provide protection

The correct and safe storage of e-bike batteries or, more generally, lithium-ion batteries already prevents numerous causes and sources of danger that could lead to a fire in the first place. Suitable battery boxes or battery bags provide effective protection against weather influences and often also against mechanical damage, as the boxes, for example, are filled with Pyrobubbles or other granulates. The e-bike batteries stored therein are protected from shocks and thus no longer exposed to a major hazard that could lead to battery failure and possibly fire.

The proper fire protection for e-bike batteries

Besides protection against shocks and environmental influences, suitable battery bags and boxes for e-bike batteries offer an important additional feature for preventive fire protection: if problems occur with the battery or even a battery fire, the bags and boxes protect the environment from fire damage.

Battery bags made of fireproof material

Battery bags are usually made of fireproof or flame-retardant material. A battery that catches fire on an e-bike or pedelec causes relatively little damage when stored in a fireproof battery bag. At the same time, battery bags also provide protection during charging, because normally lithium-ion batteries can be stored in the bags while charging.

Fireproof boxes for e-bike batteries

An alternative approach is pursued by fireproof boxes for e-bike batteries. Often the boxes themselves are not fireproof, but they are filled with appropriate extinguishing granules / extinguishing agents for e-bike batteries, which in the event of a battery fire act as an automatic extinguishing system. If an e-bike battery stored in the box catches fire, the Pyrobubbles melt and efficiently seal off the battery fire. This prevents the fire from spreading to the surroundings and usually ends the battery fire relatively quickly without significant damage.

Charging boxes for e-bike batteries with integrated extinguishing system

Charging boxes for e-bike batteries with integrated extinguishing systems. They offer an especially high level of safety. In them, the batteries can not only be charged, but the system also detects a temperature rise or smoke. It then immediately issues a visual and audible alarm. At the same time, an integrated, pressure-free extinguishing system in the alarm condition releases an environmentally friendly extinguishing and cooling medium over the e-bike batteries and thus stops the fire. Through a filter, the resulting smoke-gas mixture is directed into the exhaust management system so that no toxins can escape to the outside.

Never store defective e-bike batteries – here the risk of a much higher fire

The above explanations show the recommended precautions for storing intact batteries of e-bikes and pedelecs. Significantly greater is the danger with defective batteries: These should never be stored inside a dwelling under any circumstances, and even storage in the garage etc. carries a greatly increased risk. With defective batteries, the risks of a battery fire or a thermal runaway are significantly higher, and no one should expose themselves to this risk. If an e-bike battery is defective – whether it no longer charges, has mechanical damage (for example from a fall) or other problems – it must be disposed of immediately by a professional company. The quick and proper disposal of a defective e-bike battery is one of the absolutely essential measures of fire prevention.