Safety of today’s electric cars

What happens after an accident? Does the battery go up in flames?

The critical issue during an accident: deformation of the battery

The electronic components must be designed to be “intrinsically safe”. Intrinsically safe means that the power flow to the battery is stopped if a defect occurs in the system. Put simply: if an accident takes place, the battery is immediately and automatically disconnected from the other high-voltage components and cables to ensure the voltage is cut off.

What to do in the event of a breakdown?

For safety reasons, work on high-voltage components can only be carried out by people who have been trained for this work. Everyone else needs to stay away from these components and all orange-coloured wires!

It can become critical if the technical protective mechanisms of the drive battery are deformed by an accident and thus impaired. In a worst case scenario, the cells in the drive battery can set off a chain reaction called a thermal runaway, which sets fire to the drive battery and makes it very difficult to put out.

Crash test with two VW Ups

The structures relevant to the crash are identical in both vehicles. The battery pack was also reinforced with a frame and fitted below the vehicle. This makes it more robust but adds extra weight of almost 250 kg.

A comparison after a head-on collision at 64 km/h with 40 percent collision area (both bonnets offset by about half) clearly shows that there is no drop in safety with the VW up! due to the additional weight of the batteries. The vehicle structure does not exhibit any increased deformation values and the load values for the occupants are identical to those of the petrol-powered up! variant.

The deformation of the underbody ended far short of the battery pack and the electric shut-off for the high-voltage system reacted within milliseconds to the accident by disconnecting the connecting cable between the battery pack and the high-voltage cables leading to the electric drive via a relay system. The battery did not ignite, there was no risk of fire.

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