Lithium batteries: OVERLOOKED DANGER
They are at the heart of many electrical appliances: Lithium-ion batteries are now an invisible part of our daily lives. But it's not just smartphones, tablets and similar devices that receive their energy in this way. More and more toys on board yachts and even entire tenders are relying on lithium-ion batteries. The danger that can emanate from this technology is often underestimated.
A lithium-ion battery or lithium-ion accumulator describes a storage medium that works on the basis of lithium compounds. It serves as a generic term for a variety of different batteries - so in this sense there is no "one" lithium battery. A lithium-ion battery pack is made up of several cells, depending on the capacity. Each lithium-ion cell consists of a positive and a negative electrode, the anode and the cathode. Between them is an ion-conducting electrolyte. This guarantees the transport of the lithium ions between the electrodes during the charging or discharging process. The best-known form of lithium energy storage is the lithium-ion accumulator, in which a liquid electrolyte is used. Another important component is the separator. It prevents direct contact between the anode and cathode and thus prevents a short circuit.
UNDERESTIMATED FIRE HAZARD
In case of defects or improper use and storage, the rechargeable batteries can release their stored energy suddenly and uncontrollably. This uncontrolled release of stored energy is called thermal runaway. If thermal runaway occurs, the lithium-ion cells in the battery block heat up. One cell can reach several hundred degrees Celsius and in turn heat up other cells - a chain reaction. This can cause even chemically embedded lithium to ignite at over 600 degrees Celsius. If an attempt is made to extinguish the fire with water, a so-called oxyhydrogen explosion can occur. Due to the high reactivity of the alkali metal lithium, water can be broken down into its components and hydrogen gas is released. Since a hydrogen air mixture is ignitable in a very wide mixing ratio, even the slightest ignition source may be devastating.
The resulting fire is difficult to bring under control by conventional means. This is because if the chain reaction was triggered from the centre of the battery, it is almost impossible to reach it with an extinguishing agent, e.g. water, and thus stop or contain the reaction. If one now tries to cool such a module, the water only reaches the outer layers or the housing of the batteries. The situation is different with smaller modules, where fewer cells are used. Here, external cooling usually has a direct effect on the reacting cells. In addition, toxic and flammable gases can be produced in the process, so that deflagration can occur.
According to the findings of the German Insurance Association, physical damage, extreme temperatures and so-called deep discharge are the most frequent causes of fire in lithium batteries. The experts of the Pantaenius claims department therefore advise to always follow the manufacturer's specifications when charging, to use the original charger and to neither disassemble nor damage the batteries. In addition, the batteries must not be exposed to extreme heat or cold to avoid ignition of the batteries. In many modern devices, however, the electronics are programmed in such a way that deep discharge is not possible. In this situation, the device can no longer be used.
WHAT TO DO WHEN A BATTERY BURNS
Fires of lithium-ion batteries are considered very difficult to fight. Attempts to extinguish fires with conventional means are usually unsuccessful, as lithium-ion cells produce the oxygen needed for the fire themselves. When selecting the appropriate extinguishing agent, the size and quantity of the batteries, but also the operational conditions play a role.
Every battery fire has a high hazard potential. Only very small devices can be brought under control by using as much water as possible. For example, a burning smartphone can be extinguished with plenty of water and then placed in a larger container filled with water to cool the battery and prevent re-ignition.
If a larger battery catches fire, think of a sea scooter or hydrofoil, it can fill rooms on board with smoke within a few seconds. Persons at risk should immediately seek safety, leave the affected area and close doors. As already described, attempting to extinguish the fire with water can lead to an oxyhydrogen explosion.
In order to reduce the risk for crew, guests and the yacht itself, garages or rooms on board in which mainly toys or electrically operated tenders are stored can be equipped with an aerosol extinguishing system. This works without the addition of water and extinguishes the incipient fire at a very early stage by extracting heat. Within a few seconds, the chemical combustion process is stopped. Since the technology does not work on the basis of oxygen displacement, as is the case with CO2 extinguishers, there is no danger of people suffocating. To fully exploit the possibility of such a system, heat, gas and smoke detectors are logically required. Specialised providers such as LiCELL now also offer smaller handheld or mobile fire extinguishers that use an aerosol extinguishing agent.
INVISIBLE RISK FOR FIREFIGHTERS
Not every fire involving an electronic device is automatically a battery fire. However, not even professional fire fighters can tell whether a lithium-ion battery poses an acute danger or not. Spectacular accidents during attempts to extinguish electric boats therefore unfortunately occur again and again. Units that have a large lithium-ion battery should therefore always be handled with appropriate caution in the event of a fire. Ideally, tenders or toys with electric drives should be marked as such and arriving firefighters should be informed of this.
Caution: Even extinguished lithium-ion batteries can spontaneously re-ignite at any time. To counter this danger, there are storage boxes made of aluminium, galvanised steel or stainless steel that have been specially developed for the storage and transport of defective lithium batteries and are usually filled with special granulate or liquid extinguishing agents. These aids have long been standard on land and should not be missing on any yacht that uses battery-powered toys.