Extinguishing an e-bike battery fire

E-bikes and pedelecs have become increasingly popular in recent years. Not only senior citizens, but also commuters, leisure cyclists and even competitive athletes are increasingly discovering battery-powered bikes for themselves. To ensure an adequate range and powerful support, e-bikes and pedelecs are equipped with ever larger lithium-ion batteries, which often have capacities of 500 Wh and more. This comparatively high amount of energy can pose a real danger in the (fortunately very rare) event of a fire. This makes it all the more important to have suitable extinguishing agents and battery fire extinguishers to hand in the event of a fire, so that the battery fire can be extinguished as quickly as possible.

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

A defective battery, incorrect storage, unsuitable chargers - these are the most common reasons why an e-bike battery catches fire. Once a fire has started, Li-ion batteries are difficult to extinguish. Special fire extinguishers for batteries or small fire blankets can be an initial measure, but professional assistance from the fire department is usually unavoidable. Prevention is therefore particularly important: e-bike batteries should therefore be stored in specially developed, fireproof battery bags or boxes for e-bike batteries, as these offer good protection against the spread of a fire caused by the Li-ion battery, even with problematic batteries.

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

• How can an e-bike battery fire occur?
• What is the fire risk of 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 that are designed to prevent excessive heating or even an e-bike battery fire at an early stage. Nevertheless, it can never be ruled out that an e-bike or pedelec battery can catch fire, either as a result of a defect in the battery management system or if unsuitable chargers are used. However, the most common cause is a mechanical defect, which can have many causes, especially with e-bike batteries, and can result in a short circuit, for example. Due to the potential danger, it is generally recommended to store e-bike batteries safely when not in use, regardless of their condition. Depending on the battery size, suitable boxes for e-bike batteries include, for example, the Zarges K470 battery safe, the B&W battery case or the various boxes in the Genius Lio-Guard series. Battery cases made of fireproof material are also suitable.

Defective battery due to mechanical impact

In principle, e-bike batteries are relatively robust energy storage devices. Nevertheless, damage can occur due to heavy mechanical loads within the battery cells. Typical scenarios include accidents involving the e-bike or if the battery falls to the ground. Externally, the batteries are often still completely undamaged and continue to supply the energy for cycling as usual. If they are then reconnected to the charger, defective batteries can cause problems and even cause the e-bike battery to catch fire. However, thermal runaway can also occur when the battery is not being charged - a chain reaction in which the battery cells overheat and a fire is triggered and, in the worst case, the e-bike battery can even explode.

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

The good news first: the risk of fire with an e-bike battery is very low if it is stored and used correctly. This is also supported by the fact that you rarely hear of an e-bike fire, even though the use of e-bikes has increased significantly in recent years. Accordingly, it is not necessary to refrain from buying a pedelec or e-bike because of the fire risk of an e-bike battery, but rather to take the appropriate measures to store the e-bike battery correctly and thus minimize the risk of a battery fire.

Defective e-bike batteries increase the risk of fire

While intact and correctly used e-bike and pedelec batteries are very safe, the risk of fire increases significantly with defective batteries. Accordingly, obviously defective e-bike batteries should no longer be used, but replaced with a new battery. The defective battery must be disposed of properly, otherwise there is still an increased risk of fire. And even if, for example, the battery still looks good on the outside after a fall, there may be damage to the sensitive separator layer on the inside, which also increases the risk of an e-bike fire. It is therefore important to exercise caution and take the necessary precautions when storing and charging e-bikes.

How do you extinguish an e-bike battery fire?

If an e-bike battery catches fire, classic ABC or carbon dioxide extinguishers are generally not the first choice. Normal water extinguishers are also unsuitable as they can cause further short circuits in a live system. Special fire extinguishers for lithium batteries are the better choice: fire extinguishers filled with silicon, gel or pyrobubbles, for example, offer an efficient way of extinguishing a burning e-bike battery. However, the following also applies here: Preventive measures, i.e. preventing a bike battery from catching fire in the first place or the battery fire from causing major damage, is always better than active firefighting. It is therefore important to store e-bike batteries correctly. Even the supposedly small e-bike batteries can cause major problems when extinguishing a fire.

Important initial measures for extinguishing a burning e-bike battery

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

2. Disconnect the power supply: If possible and safe, disconnect the e-bike from the power source. Switch off the bike and remove the battery if it is safe to do so.

3. Use a fire extinguisher or fire blanket: Use a special fire extinguisher for lithium-ion battery fires based on fire classes D or F (also referred to as class D or K in some countries). 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 may even lead to a more violent reaction. See below for details of suitable rechargeable fire extinguishers. Alternatively, a fire blanket can also be used for lithium-ion batteries.

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

5. Call the fire department: If you are unable to extinguish the fire yourself or are unsure how to proceed, call the fire department immediately. Inform the emergency services that the battery 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 hazard. Do not leave the battery unattended and wait until it has cooled down completely.

The following sections explain in more detail the individual extinguishing agents that can be used as part of the initial measures.

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

Gel fire ex tinguishers work with a gel-like extinguishing agent, which can be used very efficiently against e-bike battery fires. In addition to the direct cooling effect of the gel, the high heat capacity of this extinguishing agent ensures that heat is extracted from the burning e-bike battery in the absence of oxygen.
Gel fire extinguishers are relatively inexpensive and therefore suitable for extinguishing e-bike battery fires and are highly recommended, especially for owners of e-bikes and pedelecs.

Lithium fire extinguishers for e-bike batteries

More powerful than the gel fire extinguishers are the so-called lithium extinguishers, which use lithium-X as the extinguishing agent. The silicon extinguishing agent is an aqueous dispersion in which natural silicon crystals are kept suspended in an aqueous solution. When sprayed onto a burning e-bike battery, the water evaporates, the microscopically small silicon platelets swell and fuse together to form an impermeable barrier layer. This isolates the e-bike battery fire, the thermal radiation above the barrier layer immediately drops to below 100°C and a thermal runway is prevented. The lithium extinguishers are somewhat more expensive and are often used in a commercial environment, 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 versions mentioned above, there are fire extinguishers that use pyrobubbles as an extinguishing agent. The extinguishing granulate developed by Genius is very often used when transporting Li-ion batteries, for example as granulate in the battery transport containers. In fire extinguishers, the extinguishing agent can be sprayed directly onto the burning e-bike batteries, where it extinguishes the fire. Similar to lithium fire extinguishers, however, these are also more likely to be found in commercial environments and are rarely used by private individuals to extinguish an e-bike battery fire. At the same time, you should always bear in mind that extinguishing e-bike batteries with pyrobubbles requires special fire protection concepts, which usually include not only the pyrobubbles, but also the tightly sealed battery container.

Extinguishing blankets for lithium-ion batteries

Another way to effectively fight an e-bike battery fire is to use a suitable fire blanket for lithium-ion batteries. The BRIDGEHILL Extreme Fire Blanket for small lithium batteries in particular is designed precisely for this purpose and is particularly easy to use in the event of a defect or fire on an e-bike battery. However, other manufacturers such as Vlitex also offer a comparatively inexpensive model, the fire blanket for battery packs, which can be used to fight a battery fire: Simply spread it out in front of the problem battery and then throw or place it over it. After at least 20 minutes, further measures can and should be taken to finally extinguish the burning e-bike battery.

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

As you can see in the previous sections, it is sometimes extremely difficult to extinguish an open fire on an e-bike battery. Prevention is therefore a recommended strategy to prevent the battery from catching fire in the first place and to prevent a problematic battery from causing damage to the surrounding area. The topic of e-bike battery fire protection is particularly important.

Suitable storage containers for e-bike batteries offer protection

The correct and safe storage of e-bike batteries or lithium-ion batteries in general already prevents numerous causes and sources of danger as to why a fire can occur in the first place. Suitable battery boxes or battery bags offer effective protection against the effects of the weather and often also against mechanical damage, for example by filling the boxes with pyrobubbles or other granules. The e-bike batteries stored inside are protected against impacts and are therefore no longer exposed to a major source of danger that can lead to battery failure and possibly fire.

The right fire protection for e-bike batteries

In addition to protection against impact and environmental influences, suitable battery bags and boxes for e-bike batteries offer an important additional feature for preventive fire protection: if there are problems with the battery or even a battery fire, the bags and boxes protect the environment from fire damage.

Battery bags made from fireproof material

The battery bags are usually made of fireproof or fire-retardant material. If an e-bike or pedelec battery catches fire, it will cause very little damage if it is stored in the fireproof battery bag. At the same time, the battery bags also offer protection when charging, as the Li-ion batteries can normally be stored in the bags while charging.

Fireproof boxes for e-bike batteries

Fireproof boxes for e-bike batteries offer an alternative approach. Although the boxes themselves are often not fireproof, they are filled with appropriate extinguishing granulate / extinguishing agent for e-bike batteries, which acts as a kind of automatic extinguishing system in the event of a battery fire. If an e-bike battery stored in the box catches fire, the Pyrobubbles melt and efficiently encapsulate the battery fire. This prevents the fire from spreading to the surrounding area and usually ends the battery fire relatively quickly without any major damage occurring.

E-bike battery charging boxes with integrated extinguishing system

Charging boxes with integrated extinguishing systems offer a particularly high level of safety. Not only can the batteries be charged in them, but the system also detects a rise in temperature or smoke gas. It then gives an immediate visual and acoustic alarm. At the same time, a pressure-free, integrated extinguishing system sprays an environmentally friendly extinguishing and cooling agent over the e-bike batteries in the event of an alarm, thereby stopping the fire. Filters channel the resulting smoke/gas mixture into the exhaust management system so that no toxic substances can escape.

Never store defective e-bike batteries - there is a greatly increased risk of fire here

The above explanations show the recommended precautionary measures for storing intact e-bike and pedelec batteries. The danger is much greater with defective batteries: these should never be stored inside a home under any circumstances, and storage in a garage etc. also poses a greatly increased risk. The risk of a battery fire or thermal runway is significantly higher with defective batteries and nobody should expose themselves to this risk. If an e-bike battery is defective - regardless of whether it can no longer be charged, has mechanical damage (e.g. due to a fall) or causes other problems - it must be disposed of immediately by a specialist company. The quick and professional disposal of a defective e-bike battery is one of the absolutely essential fire prevention measures.