A fire in an electric vehicle differs from a petrol or diesel fire, meaning that emergency personnel require more knowledge about how to manage burning electric vehicles.
There are currently in the region of 50,000 electric and hybrid vehicles on Swedish roads and that number is increasing. Electric vehicles run on lithium batteries, which have the advantages of a long life and high energy density, i.e. they are able to store large amounts of energy. However, they also have disadvantages, including the risk of fire and explosion.
“A lithium battery may catch fire, either due to an internal short circuit or external causes such as overcharging. Internal short circuits are generally related to production quality, while external issues are due to operation or the construction of the vehicle itself. Hoverboards, which are also powered by lithium batteries, experienced a problem a few years ago when a number of products burst into flames, generally due to the use of non-standard chargers that continued to charge even after the battery was fully charged. In electric vehicles, this risk is minimal because they are inspected and have inbuilt safety systems.” explains RISE researcher Lars Fast.
Advice on how to design batteries
RISE has developed a risk-assessment report that offers advice on how to design batteries and where they should be placed in vehicles in order to increase electric vehicle safety. For example, ventilation is one important parameter, as the gases that build up when a lithium battery heats up must be vented to avoid the risk of explosion. When it comes to placing a battery, it should ideally be located in the vehicle’s safe zone, in the centre between the axles where most protection is provided in the event of a collision.
Even if the risk of explosion is small, there are other risks, for example a battery fire. This may occur as a result of incorrect use such as exposing the battery to extreme heat or if the battery is damaged in a collision. Any smoke formed will be toxic and there is a need for greater knowledge of both burning batteries and electric vehicles.
“Because there are still relatively few electric vehicles on the road, emergency services are not always aware of how to deal with them. They lack awareness of the types of gases emitted and are sometimes uncertain of how they should deal with a burning vehicle,” explains Lars Fast.
Emergency personnel needs new knowledge
The smoke produced by a burning electric vehicle may contain hydrogen fluoride, a hazardous substance that may penetrate protective clothing. It is therefore important that emergency personnel have the requisite knowledge. If the battery is the source of the fire, it may also prove difficult to extinguish the vehicle. A battery fire demands a great deal of chilling and the battery is enclosed in a sealed box, making it difficult to access. There is also a risk that an electric vehicle will reignite long after the fire is extinguished. This is due to a phenomenon called ‘thermal runaway’, in which the temperature of the battery rises due to an internal reaction.
“At RISE we do a great deal of work with training and information, including holding theme days and scientific conferences. This is intended to provide both emergency personnel and other municipal staff with knowledge about electric vehicles so that they feel confident in their ability to deal with accidents,” says Lars Fast.
Three tips for electric vehicle drivers
- Always follow instructions from the manufacturer or supplier of your electric vehicle and use the intended charging equipment.
- An electric vehicle may begin to burn long after a collision has occurred. Always bear this in mind when parking you car in the garage after a collision. (A Chevrolet Volt began to burn three weeks after a test crash.)
- You should also bear in mind that exhaust fumes vented from batteries are a health hazard.