Maximising safety in advanced battery systems
01 September 2020
In advanced battery systems, the quality of the power electronics helps determine the quality of the final product. This is emphasised in the latest battery power management and charging systems that use wide-bandgap semiconductors and improved power topologies. In such advanced electronics, if the safety systems do not work quickly and reliably, the entire battery system can suffer a catastrophic failure that could seriously impact the product and its user.
In life-critical application spaces such as automotive safety, the importance of fail-safe subsystems is paramount. The battery system in an EV is similar to the petrol tank in a traditionally fuelled vehicle, in that the stored energy needs to be safe. There is a considerable amount of energy in a modern battery, and catastrophic failure can certainly lead to such things as thermal runaway (better known as fire!).
Managing short circuits
The higher cell densities in advanced battery systems demand proper safety protocols as the power levels involved present a significant challenge when it comes to managing short circuits. To create a robust and safe system that helps ensure reliability over a given vehicle’s lifetime, manufacturers must integrate high-performance components into their designs.
Fuses, or similar devices, are required circuit-protection components that protect the system in the event of a short circuit by breaking the line under specific conditions. There are many types of fuses, but the primary element in each is a piece of engineered conductor, usually metal and rated to fail (i.e melt) in a controlled manner under the raised line temperature conditions from a short circuit. This destructive protection method ensures the safety of the circuit by completely severing the power source.
However, this burn-out response has some drawbacks. Most notably, a power circuit under load will not necessarily have a consistent flow of current. In designs requiring pulses of high power, the wide operating range of the current drives the use of a higher current fuse to avoid nuisance tripping, but this leaves the system more vulnerable to overheating and thermal issues. That, and the non-reversible aspect of fuses, has led to the increasing use of electromechanical safety devices like circuit breakers, which can be reset as they do not rely on destructive elements to function.
Read the full article in the September issue of DPA.
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