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Volvo Cars takes on safety challenges involving electric cars
23 September 2009
Volvo is currently conducting extremely wide-ranging and thorough analysis of a variety of safety scenarios for cars with electric power. Through advanced automatic monitoring of battery status and by encapsulating the battery and protecting it effectively in a collision, the result is a comprehensive safety package of the very highest class.
Volvo imposes the same high safety standards on all its products irrespective of car type, fuel or power source. The aim ahead of the launch of any new car model is to improve safety for the vehicle's occupants. Having said that, the safety-related challenges may differ depending on the type of driveline and fuel being used.
"A holistic approach and real-life traffic conditions are always the starting-point for Volvo's safety work. Based on our massive database featuring input from actual road accidents, we know where the focus must lie in everyday traffic conditions. The solutions we have developed for our forthcoming electric cars therefore take into account the situations that are unique to this type of car," says Volvo Cars' safety expert, Thomas Broberg.
For Volvo's safety engineers, work on a new power source is not particularly dramatic. Rather, tried and tested working methods are applied in a well-oiled process to obtain the best results. At the same time, work on electrification is naturally being approached with a great deal of humility and open-mindedness. Everything from the way the cars are produced, used and serviced to the way they are recycled is analysed thoroughly and the information obtained is used to shape the development of the final production car.
Comprehensive testing under way - and there's more on the way
Volvo's safety tests take place in several different stages. First at component level, then for whole systems and finally the complete car is safety-tested. Both virtually in the computer, and physically in Volvo's technically advanced crash-test centre.
"At present we are conducting tests at component level to see how the battery is affected by harsh braking and the subsequent collision, examining the results from several different angles. We are also carrying out, for the first time, advanced crash tests in full scale to evaluate the technology in electrically powered cars," reveals Thomas Broberg.
Volvo is using its unique know-how from actual traffic conditions when carrying out detailed testing and verification. What is more, the company bases its entire test regime on the general requirements and protocols of the industry's safety institutes.
"We may well see further down the line that cars powered solely by electricity can be made even safer than cars with combustion engines. We like to see electrification technology as an exciting challenge - even from the safety viewpoint," says Thomas Broberg.
Preparation for every phase of the accident sequence
When Volvo analyses safety scenarios on the basis of actual traffic situations, the engineers use a model that illustrates the sequence of events in a real-life road accident. The whole process is divided into five phases: from the normal driving situation to after the accident has occurred. Based on these five phases, Volvo develops new safety solutions and improves existing ones.
This approach covers the entire sequence from giving the driver optimal preconditions for safe driving, for instance by providing good comfort and stability-enhancement functions, to systems that alert the driver or automatically step in to avoid a collision. And if a collision is unavoidable, Volvo's cars offer highly advanced impact protection as well as solutions that assist both the driver and the emergency rescue services after the accident has occurred.
Unique solutions for electric cars
All Volvo's existing safety systems will also be available in the company's electric cars. However, electric power also adds new possible safety scenarios to the overall picture and these too must be dealt with.
In the safety work that is currently being undertaken in the field of electrification, Volvo's safety experts have meticulously analysed the five accident sequence phases and developed unique solutions for the battery and for protection of the occupants as necessary.
- Normal driving: A comprehensive and advanced monitoring system keeps watch and ensures that each cell maintains the correct voltage level and optimal operating temperature by regulating the cooling system. This is of significance to both safety and battery capacity. In the event of any deviation, the battery is automatically shut down as a preventive measure.
- Conflict:. The battery fitted to Volvo's plug-in hybrid weighs about 150 kg. This added weight creates new conditions for the vehicle's dynamics and alters the car's behaviour, for instance in fast avoidance manoeuvres. Volvo's existing platforms and braking systems can handle the increased mass, and Volvo's DSTC stabilisation system (Dynamic Stability and Traction Control) helps the driver contain the situation.
- Avoidance: If a collision is imminent and the driver finds it difficult to handle the situation, the vehicle can activate automatic safety systems such as Collision Warning with Full Auto Brake and City Safety to avoid or reduce the effects of an impact. These systems can be used in cars with electric power just as they can in other types of car.
- Collision: In order to reduce the effects of a collision, the battery is well-protected in the rear of the car between the wheel housings, separated from the car's crumple zones. The battery is also sturdily encapsulated.
Through Volvo's studies of actual traffic accidents, the safety engineers know that this location helps protect the battery in rear end collisions. What is more, steel beams and other parts of the structure around the battery are reinforced to protect the battery from being affected in the case of a collision.
If the battery is damaged, resulting in gas leakage, there are special evacuation ducts that lead the gas out under the car without any contact with the occupants. In the event of extreme heat, the occupants are shielded by the battery's encapsulation.
At the very moment of impact, crash sensors linked to the battery send information about the collision to the car's computer, which automatically shuts off the power supply to prevent the risk of a short-circuit
- After the collision: In addition, the battery has a security cut-out that functions like a household earth fault circuit breaker. It shuts down and isolates the battery if the current travels in the wrong direction, for instance if two cables are pressed together as a result of an accident.
Volvo also works in close cooperation with the emergency rescue services, providing them with detailed instructions on how best to handle various Volvo models in the event of an accident.
Safety in connection with servicing
The cars are equipped with a service cut-out to quickly and safely disconnect the car's power supply.
Recycling and safety
Volvo Cars and the battery manufacturers have far-reaching product responsibility as regards both production and recycling. This ensures proper handling of the battery when it comes to the end of its life in the car.