EVs or Electric Vehicles are the vehicles which have batteries to power their electric motors and energize propulsion systems. These batteries have huge amount of energy stored in small volume. Presence of batteries in electric vehicles poses great risk of fire and explosions in these vehicles.
In this article, we will explore reasons associated with EV batteries catching fire. In the end, a detailed safety analysis will be presented to help readers understand their battery vehicles better and reduce chances of fire, explosion, or ignition.
Why EV Batteries are Vulnerable?
Before discussing reasons of EV fires, it is crucial to know batteries placed in EVs. Because fire eruption in EVs happens mostly because of batteries in them which are storing high amount of energy.
Lithium-ion batteries are most used batteries in EVs as of now. These batteries have flammable electrolyte to make the battery conductive. Heat generation in battery due to any reason can lead to thermal runaway and cause the battery to catch fire.
Now, we can relate it to size of battery also. It is required that EV batteries have high capacity or store large amount of energy. As battery size increases, risk of hard-to-extinguish fire also increase in presence of inflammable electrolyte.
Reasons Behind EV Batteries Catching Fire
Thermal runaway is considered as the primary cause of EV battery fire. This thermal runaway could happen because of various reasons ranging from physical damage to short circuits. Here, we will see various reasons associated with thermal runaway or EV batteries catching fire.
On a broader scale, reasons of EV battery fires can be categorized into two 类型: accidents and manufacturing faults.
Accidents are regarded as incidents which shouldn’t have happened, for example collision and charging mishap. After an accident, user might be conscious and expect fire. So, there are high chances for him/her to take appropriate action.
Fires due to manufacturing faults are more concerning and pose higher safety risks because these are more random and unexpected. Considering that li-ion battery fires are intensive and hard to extinguish, these unexpected fires are deemed more concerning.
Here, all potential reasons of EV battery fires are detailed.
热失控
Thermal runaway is the situation when battery enters self-sustaining chain reaction where it keeps producing heat which overwhelms its cooling mechanism.
Lithium-ion battery in EVs has a flammable electrolyte combined with substantial amount of energy stored in its cells. If EV battery starts producing excessive heat due to accident or any other reason, battery could cross its safe temperature limit, leading to fire or explosion.
Thermal runaway could happen because of manufacturing defects, chemical reactions going wrong, or mechanical damage. Furthermore, external heat, over charging, over discharging, and use of wrong charger can cause thermal runaway.
过度充电
Every EV battery is designed to store a specific amount of energy which refers to its capacity. If a battery is overcharged and forced to store more energy than its capacity, then there are chances of thermal runaway, battery capacity degradation, battery damage, and fire in worst case scenarios.
Physical Damage
If an EV battery gets damaged because of fall, throw, piercing, weight, accidents, debris, or any other reason; internal structure of the battery cells will be affected. Specially, anode and cathode might come in contact leading to short circuits and thermal runaway. So, physical damage could lead to fires and explosions in EV batteries.
It must be highlighted that EV batteries are highly prone to physical damage because of their usage on roads and so there might be cases when their batteries might get damaged during collisions and catch fire.
Manufacturing Faults and Poor Quality
Internal structure of an EV battery might not be as per standards due to manufacturing faults. This could lead to plating, short circuits, and fires.
Manufacturing fault could also be associated with faulty thermal management system which might be unable to detect and manage battery heat effectively and lead to EV battery fire and explosion at some point.
Use of poor quality material for any component (electrodes, contacts, separator etc.) might also cause problems including fire.
Extreme Ambient Temperatures
Recommended operating temperature range for most lithium-ion batteries falls between 15 and 35°C. Anyhow, they keep operating safely between -20 to 60°C, though efficiency is reduced. If ambient temperature goes far above or below the mentioned safe temperature range, then various safety risks arise including fire and explosion.
At subzero temperatures, a phenomenon named ‘Lithium-ion battery freezing’ could happen which increases internal resistance, reduces capacity, caused dendrite growth and short circuits, and leads to fires and explosions. So EVs with lithium-ion batteries have risks of battery fire and explosion while operated in extremely cold weather.
Similarly, EV battery can catch fire in extreme hot weather also. At high temperature, battery would not be able to dispense its generated heat effectively leading to thermal runaways and fire.
Wiring Problems
Problems associated with wiring and connections bring about electrical failures which could result in short circuits, excessive heat generation, and fire in worst scenarios. Many wiring problems caused by corrosion, loose connections, and wrong polarity in EV batteries can be avoided easily.
Inadequate or Faulty Protection Circuit
Overcharging, overloading, or short-circuiting impact battery health negatively and can also cause fire in EV batteries. These problems can be avoided if appropriate and functioning protection circuit is used. Absence of such circuit will increase the chances of fire and explosions in EV batteries.
Risks Associated with EV Battery Fires
Any kind of fire, inherently, has risks associated with it. Anyhow, type and extent of these risks vary greatly depending upon substance being burnt. Likewise, EV fires erupting majorly because of batteries have some major risks associated with them which are mentioned here.
- EV battery fires are very intense and hard to extinguish so they last for longer duration of time.
- EV battery fires generate extreme heat and release flammable gases.
- EV battery fires become ongoing hazard because these fires can reignite after hours or days of being put-out.
- Accumulation of released flammable gases in closed garages or parking lots for EVs might lead to explosions.
- EV fires or EV battery fires might cause human injury and property damage.
Improving Safety Factor for EVs:
Safety measures adopted at individual level, industrial level, as well as regulatory/compliance domain can reduce the risks of EV fires. These measures are, indirectly, aimed at improving safety factor of lithium-ion batteries installed in EVs. Here, some of the key safety measures are mentioned.
Employing Advanced Battery Management System
To avoid over-charging, detect short circuits, identify thermal runaway situation, and notify voltage imbalance; use of advanced battery management systems is crucial. Modern EVs and even individual battery packs come equipped with BMS that enhance safe use of EVs.
Handling with Care
Users must consider the fact that physical damage could harm the EV battery and ignite fire. So, it must be handled with care in all situations including storage, charging, and operation. If one electric vehicle experiences accident, then battery must be removed and taken to some expert provided it is safe to take these steps.
Careful handling is also applicable for charging phase. For example, EV shall not be charged in extreme hot or cold weather as this increases the risks of EV fires.
Avoiding Overcharging
Overcharging causes excessive heat production which could lead to thermal runaways and fire. So, it must be taken care that battery doesn’t get overcharged. Use of appropriate battery management system is crucial here. In case of EVs, owners/drivers must make sure that they visit certified charging stations for safe charging.
Another key factor to keep the battery from over charging is the use of recommended and approved chargers by battery manufacturer. For EVs, chargers are standardized and as an EV owner, you must know which charger is suitable for your EV. So, you could use just appropriate charger/chargers.
Regular Inspection
Usually, EV batteries show signs of damage before absolute failure. These signs include cracks, corrosion, abrasion, heated casing, sparking sound, rapid energy drain, burn marks etc. If batteries installed in EVs are inspected regularly and appropriate action is taken upon finding one or multiple signs of anomaly, chances of EVs fires and explosions can be reduced significantly.
What to do if Your EV Catches Fire?
If your EV catches fire either on road or within a parking lot, you must take some quick actions to save lives and minimize economic loss. As of now, standard or code related to fire safety is not developed by National Fire Protection Agency. Anyhow, with heavy employment of EVs, progress is expected in this regard.
Here, some generic guidelines are mentioned to minimize the harm arising from EV fire.
- Evacuating vehicle and surrounding area is the most important step upon EV fire eruption. If EV catches fire near or under a residential building, commercial plaza, or other alike space; activate building’s fire alarms.
- Contact emergency service and mention that fire is associated with electric vehicle.
- EV fires are normally because of batteries as mentioned earlier. Use of fire blankets is not effective for battery fires because it won’t stop thermal runaway and there would remain high chances of reignition.
Moreover, fire blankets will just stop oxygen supply and smother the flame for short period but they will also let flammable gases accumulate beneath which might lead to explosion.
- Water can be used to contain the fire and cool down the battery. Though, water alone is not enough to extinguish the fire completely. Anyhow, water can be used until emergency service providers arrive.
- Do not try to restart your vehicle after fire is extinguished. Instead, contact trained professionals to inspect and handle the vehicle.
结论
EV fires are mainly because of electric batteries which are basic energy source in these vehicles. Causes of EV fires originating from electric batteries include thermal runaway, short circuiting, operation or storage in extremely hot or cold environment, over charging, physical damage, use of sub-standard battery, and so on. EV fires are different from that of ICE based conventional vehicles. These fires are hard to extinguish, release flammable gases, produce extreme heat, and are prone to reignition. So, in case of EV battery fire eruption, special measures must be taken to save lives, minimize economic loss, and extinguish fire.
常见问题
What is the ratio of EVs catching fire?
According to an estimate, approximately 0.025% EVs sold in the market caught fire as of now. Careful handling, training, and wide spread education can reduce this ration further.
What is an EV fire blanket?
Recently, EV fire blankets are designed which are effective for extinguishing battery fires. Anyhow, this technology is still under development.
Are EVs less safe than ICE based vehicles?
Electric vehicles are safe overall, but their batteries can catch fire sometimes.
According to stats, EVs are less likely to catch fires in comparison with ICE (Internal Combustion Engine) vehicles. Anyhow, whenever they do, it is mostly because of battery related problems which might cause difficult-to-extinguish fire.
