New early warning system should provide better protection against burning lithium-ion batteries.
Burning lithium batteries in cars can quickly become a danger to people and the environment. Previous warning systems only react a few minutes before a battery spontaneously ignites, known as thermal runaway. The Federal Institute for Materials Research and Testing (BAM), together with Vitesco Technologies, a leading international provider of modern drive technologies and electrification solutions, is developing an early warning system that indicates possible dangerous damage to the battery weeks in advance and thus helps to protect people.
Legal regulations in the European Union stipulate that an electric car must emit a warning signal to people in the passenger compartment at least five minutes before the battery runs out of heat. This usually happens via the battery management system (BMS), the electronic control unit of the battery. The BMS monitors the performance and condition of individual battery cells and cell groups.
So far, total battery loss has been almost inevitable
Previous warning systems register defective changes in the battery via sensors that react to suspicious temperature or pressure changes within the battery. The disadvantage: An alarm is only triggered when the battery is already seriously damaged. Thermal runaway and therefore probably complete destruction of the battery are usually unavoidable at this point.
In cooperation with Vitesco Technologies, BAM is researching a warning system that indicates critical changes in individual battery cells earlier and thus helps to avoid total loss. The basis of the innovative early warning system is a process that continuously measures and analyzes the electrical alternating current resistance – the impedance – in the cell.
New system measures and analyzes impedance
Tim Tichter, who is researching the project at BAM, said:
A change in impedance can indicate various defects or undesirable conditions.
“These can be caused, for example, by vibrations, shocks, thermal loads, material failure or even manufacturing errors. Regardless of the cause, a change in impedance is to be expected in any case.”
To date, long measurement times have been necessary for meaningful impedance analyses. They prevent the implementation of such analyzes in a BMS. The innovative approach of the project team: It modifies the measurement methodology so that a high acceleration in recording and processing the impedance data is possible.
The early warning system based on this technology is intended to initiate a service in an emergency or to trigger immediate protective measures, such as switching off individual cells. This not only makes it possible to avoid serious damage to lithium batteries and thus save costs, but also to better protect people from the dangers of a battery fire.
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New early warning system should provide better protection against burning lithium-ion batteries. source
