Why are high-end cars catching fire? The answer lies fuel flashpoint, overwhelmed wires, failing sensors and unstable batteries
The car crash involving cricketer Rishabh Pant came as a shocker as 2022 was drawing to a close. His Mercedes-Benz had hit a road divider on Delhi-Dehradun highway at high speed and caught fire. He managed to break the windowpane and come out in the nick of time.
While Pant was lucky enough, a quick internet search reveals tht a number of luxury cars were involved in accidents last year. In February last year, a Mercedes GLA model met with an accident and burst into flames. There have been report of a couple of BMW cars, including a 5 series model, catching fire while parked or on the move in traffic. Former Tata Sons chairman Cyrus Mistry's Mercedes car was involved in a terrible accident that killed him last year.
There were 10-15 reports of premium internal combustion engine (ICE) cars, including Kia Seltos, Maruti Swift Dzire and Volkswagen Vento, bursting into flames in various incidents, not necessarily in the aftermath of a crash.
Why are high-end cars that come loaded with safety devices catching fire? why are vehicle-alert systems not warning the driver in time? Even as the auto industry is talking about making cars better and the government is making laws more stringent to make roads and motor driving safer, what are the loopholes that need to be plugged?
WHY ARE PREMIUM CARS CATCHING FIRE?
Industry experts maintain motor vehicles can fail despite having safety features as these are manmade. Having said that, a car catching fire is connected to its fuel characteristics. Petrol is flammable and catches fire easily. while the flashpoint of diesel globally is above 50 degrees C, in India, due to reasons related to cost and productivity, it has been kept at 35 degrees C. In the case of a Volvo bus catching fire in Hyderabad in October 2013, wherein 45 passengers were burnt alive, the fire was tracted to the diesel flashpoint.
In the accident involving Pant, the car hit a divider at high speed. At that speed, the friction between the car and divider would set anything on fire, industry experts point out. Another expert says that when Pant's car crashed, its fuel lines were ruptured. THe spark caused by the massive crash would have ignited the fire in the spilt fue line.
WHY HAS THE FLASHPOINT FOR DIESEL NOT RAISED IN INDIA?
The India automobile industry has been asking for diesel flashpoint to be raised to the global standard for the last two years. The Bureau of Indian Standards has to tweak the standards for it. This will involve modifying the refining processes that might compromise the profitability of the oil, refineries. THis is leading to hesitancy on it, say industry sources.
Ever since the auto industry demanded a higher diesel flashpoint level, multiple committees have been formed to look into the shortcomings. Recommendations were also proposed, but no action has been taken after that. Sources say the lack of interest stems from the fact that the committees were dominated by refiners. They say refineries are not okay with changes. In petrol, specifications are not an issue as the fuel evaporates easily.
WHY ARE STANDING OR MOVING CARS CATCHING FIRE?
Premium cars sport a host of electrical and electronics systems. Besides, many consumers get extra fittings and accessories such get extra fittings and accessories such as sound systems or additional lightings. These accessories are not designed to be part of the electronics system of the vehicle. So, the writing harnesses carry additional loads causing sparks in the absence oof properly tolled-up connectors.
Sometimes, repairs may not have been done properly. For instance, the fuel lines may have been fixed lossely. The leaking petrol/diesel may find a hotspot that causes fire in a standing or a moving car.
In the case of a Mercedes or a BMW car that has been thoroughly validated and tested for safety, there is a possibility that there could be some losse connections or excessive overloading of power lines that causes short-circuiting.
An expert says that any vehicle can fail, but the safety requirements in the design stage should configure failure in the in a safe condition so that no hazard is caused to the driver and co-passengers. Today, cars have electronic circuits in almost every component, like tyre-pressure monitoring sensors.
WHAT CAUSES FIRES IN ELECTRIC CARS?
Last June, a Tata Nexon electric SUV was the first electric car to be engulfed in flames. Globally, many Tesla cars have caught fire. According to a report by Business Insider, in the case of a Tesla Model X that caught fire in the United States last December, the driver pointed to miscalculations by the Autopilot mode that led him to losing control over the car. Tesla has also reported a number of battery fires. With high-voltage lithium-ion batteries, the thermal-management system, which keeps the batteries cool, has to be foolproof.
In India, due to its warm climate, the safety validation, optimisation and fine-validation, optimisation and fine-tuning process of the battery-cooling system are critical. A good understanding of control theory, embedded software development, power electronics, mechanical systems and thermal management is needed to develop a robust automotive software for high-voltage electric vehicles (EVs).
"Fires have to do with charging and discharging of lithium-ion batteries resulting in thermal management going wrong. Battery management system (BMS) and power electronics take care of thermal properties and overheating. If they are not able to control it, there is a possibility of fire," says an expert.
Allabaksh Naikodi, an EV expert, points to failure at the design evaluation, testing or validation stage of the vehicle to consider specific conditions that could trigger the failure mode in a vehicle, leading to fire.
He says, globally, operating temperatures for batteries are 50 degree C maximum after which the battery becomes unstable and goes into economy mode. This is where BMS becomes critical. Tesla normally uses large batteries that use less power so that the problem of battery temperatures rising very high does not arise. Also, worldwide, operating temperatures normally hover around 30-35 degree C. This leaves the battery with enough cooling capability.
In India, where the battery cost alone is 50-60% of the vehicle, automakers put a large motor with a smaller battery that discharges faster. If its capacity is at 40% and the demand is more, then thermal management becomes difficult. All these factors have to be considered in design. If hazardous situations are not considered at the design stage, the there could be a failure due to the presence of a large electronics circuitry in the car.
WHY DOESN'T THE VEHICLE ALERT SYSTEM GET ACTIVATED?
An accident followed by a fire happens in milliseconds, leaving little scope for the vehicle to sound an alert. Proper grounding and shielding of electronic circuitry are very important to prevent this. In case of a short circuit, this takes the current to the ground and absorbs any shocks. It also gives an alarm to the control system to go into safe mode, better know as insulation-resistance monitoring. For this, design for failure mode and defect analysis in a particular condition have to be considered while it is being developed, says Naikodi.
WHAT ACTIONS IS THE GOVERNMENT TAKING?
Last August, the Ministry of Road Transport and HIghways constituted an expert committee chaired by Tata Narsingh Rao, director, ARC, Hyderabad. The committee, which had members from the Defence Research and Development Organisation (DRDO), Indian Institute of Science (IISc) Bengaluru, National Science and Technology Laboratory (NSTL) Visakhapatnam, and the Indian Institute of Technology additional safety requirements in the existing battery-safety standards notified in the Centra Motor Vehicle Rules.
Based on the recommendations, the ministry, on August 29, 2022, issued amendments pertaining to requirements for motor vehicles of L category (vehicles with less than four wheels and a quadricycle) with electric powertrain, and specific requirements for electric powertrain of motor vehicles of M category (vehicles with at least four wheels used for carrying passengers) and N category (vehicles with at least four wheels used for carrying goods which may also carry persons in addition to goods). These include additional safety requirements related to battery cells, BMS, on-board charger, design of battery pack and thermal propagation due to internal cell short-circuit.
The notification to mandate standards for respective categories of EVs was effective from October 1,2022.
The ministry also issued draft notification August 2022 mandating conformity of production of traction batteries used in electric powertrain vehicles. It also came into effect from last October.