New batteries are being developed at a rapid pace. The quest for better batteries also means that the contents of batteries are changing, placing increasing demands on safety testing. RISE has both the expertise and the infrastructure to help manufacturers ensure that the batteries they use are safe. In the autumn of 2023, RISE opened a first-of-its-kind laboratory for safety-critical battery testing.
The global battery market is growing rapidly and is expected to be worth more than $310 billion by 2027, largely due to the increased focus on clean energy and electrified vehicles, according to a report by Research and Markets. Batteries have become a key to solving the climate crisis, and the quest for more efficient batteries is ongoing. However, before a battery is put on the market, it needs to be tested, especially from a safety perspective.
Since the autumn of 2023, a unique laboratory for safety-critical battery testing has been located in Borås. Here, batteries are subjected to vibrations, mechanical shocks, extreme temperatures and provocations to ensure safety and market approval. The laboratory gives customers access to a world-leading and explosion-proof test environment, while benefiting from RISE's long experience and expertise in batteries. Battery testing at RISE means time and cost effective battery testing with the greatest possible respect for the environment.
"We test all types of batteries and subject them to a variety of stresses. In the laboratories, we can subject them to extreme scenarios in a safe environment, such as overcharging or exposure to heat, to measure what gases are released, what energy is released, or what the course of a fire looks like. We can also subject the batteries to mechanical stress to see how different types of damage can cause thermal runaway," says Max Rosengren, battery safety expert at RISE.
Battery capacity as a competitive advantage
Today, battery capacity is a competitive advantage and an important argument when a consumer chooses between different products and brands. This means that battery manufacturers are constantly developing batteries, which in turn places greater demands on testing.
"We see new types of battery cells coming on the market all the time, and when that happens, new tests are required," says Max Rosengren. "We can't rely on previous tests because the contents of the batteries are different.
The testing and safety system requirements for batteries vary depending on how they are used. But whatever the application, battery manufacturers need to have a good understanding of protection, storage and monitoring.
"In the automotive industry, where testing requirements are higher, battery design and safety systems are often of better quality than what we see in other industries, such as cheaper leisure products," says Max Rosengren.
We see new types of battery cells coming on the market all the time
Protection in battery and product
When batteries are manufactured, various forms of protection are built into both the battery and the product in which it will be used. The main concern is to protect the battery from what is known as "thermal runaway", where a cell overheats and can produce toxic and flammable gases. The heat and potential ignition of the gases can easily cause neighbouring battery cells to "rush", creating an escalating scenario that must be prevented.
"You have protection where the voltage and temperature are monitored, and then there is also built-in mechanical protection in the battery cells, where some are disconnected if something happens, so that the energy can neither enter nor leave the cell," says Max Rosengren.
RISE's battery safety testing is largely concerned with what happens if these built-in protections fail.
"If a predicted scenario occurs, there is often protection against it," says Max Rosengren. "But sometimes several different failures occur at the same time, leading to unexpected and dramatic events.
New applications bring new risks
A current safety risk where serious incidents can occur is when used batteries are moved from one area of use to a completely different one.
"A used battery from a crashed electric vehicle may be resold and used in a solar panel installation. Then the car's monitoring system is no longer being used, but the solar panel factory's system is monitoring the battery, and this can lead to defects," says Max Rosengren.
Another situation in which fires can occur is when electric cars are involved in accidents. However, Max Rosengren believes that the location of the batteries in electric cars means that the likelihood is not too high, and that the available statistics indicate that the likelihood of a fire is no greater than in collisions with conventional vehicles.
In fact, fire incidents involving electric cars have often been attributed to causes other than the battery. This is an important detail from a safety point of view, as a 'thermal runaway' is very difficult to stop.
"As the battery is often placed low, it may not be involved in the fire very quickly. Tests show that it often takes more than 30 minutes and the car is completely burnt out before the battery is involved," says Max Rosengren.
Tests at RISE have also shown that the size of fires in electric cars is of the same order of magnitude as fires in conventional cars.
In other words, it is not necessarily the case that electric cars are more flammable or that the consequences are greater when they do catch fire. However, the risks are different and new for us to deal with. For example, the fact that they can be very difficult to extinguish, or that they can rapidly generate gases in a thermal runaway. These can be very toxic and can cause an explosion.
Electric cars require different handling
"To prevent thermal runaway from spreading to the other cells in the battery, the battery must be cooled. Water works well for cooling if the battery is accessible. However, a battery cell that is already in thermal runaway cannot be stopped and can continue to generate heat even when fully submerged in water. Cooling can stop the fire from spreading further," says Max Rosengren.
However, extinguishing the flames from a battery is not always the best solution. It can allow the flammable gases to build up and cause an explosion. The risk increases if the car is parked in a garage or other enclosed space.
Once the gases from a runaway battery have started to burn, the likelihood of an explosion is relatively low, says Max, and extinguishing the fire is mainly a matter of preventing it from spreading.
"The right mixture of flammable gas and air is required for an explosion to occur, so it is not very likely in an open battery fire," says Max Rosengren and continues. However, it is important never to be close to a battery fire. Like any other fire, battery smoke and gases are toxic and can cause serious damage – even to small batteries.
Electric cars also need to be handled differently after a crash. Because it can be difficult to determine the condition of the battery, electric cars have been known to continue to burn long after the collision, making aftercare more difficult.
