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EVs immobilised by flat batteries or breakdowns

A few weeks ago while driving back from a weekend away we came across several long queues on the Autobahn apparently due to stuck vehicles. One, on our carriageway, was caused by a car half on the hard shoulder and half in the slow lane. The police were there and I couldn’t see why two police officers and the driver couldn’t move the car a few meters on the level. A little further on there was a car stopped in the middle lane of the other carriageway. Again the police were in attendance but seemed unable to move the vehicle to the hard shoulder. As there was a good 5km of queue behind this one there should have been enough people to pick it up and carry it off the road.

After some internet searching I came across this article:

https://www.motoringresearch.com/car-news/transport-minister-astonished-hazard-electric-car-motorway-breakdowns/

“When an electric vehicle ceases to function, it stops; it does not coast in the way that other vehicles do,” said Barnoness Randerson, Lib Dem transport spokesman, during the debate.

“Smart motorways are supposed to be the future, but the future is electric. Those vehicles stop very suddenly. They also cannot be towed; they have to be put on a low-loader, which is a much more complex and longer process that will put rescue teams in greater danger.

Indeed, during a test of real-world electric car range, Carwow found that some EVs were “difficult to move” when the batteries were run truly flat. Most cars in the test ‘locked up’ once they were out of juice. The tested included everything from the Tesla Model 3 and Audi E-tron, to the Kia e-Niro and Nissan Leaf.

 

Is this true/realistic or has the problem been somewhat exaggerated? I am used to manual cars with conventional handbrake that can easily be pushed. Are EVs such a problem to move when something goes wrong? What about conventional cars with electric handbrakes, can they get stuck as well?

Parents
  • Thank you all for the information. There seem to be multiple problems here:

    Failure of the 12V system so that the steering cannot be unlocked. This seems to apply to IC vehicles as well but shouldn't normaly happen when underway, only after a full stop and locking of the car.

    Failure of the 12V system so that the handbrake or parking lock cannot be released. This would also apply to IC vehicles but again shouldn't happen when underway but maybe if stopped in a queue. There appear to be manual release options but most people do not know about them.

    Failure of the EV traction system so the vehicle is hard to move/imobilised. This would be dependant on the individual system. Putting a short circuit accross a PM motor will make it hard to rotate but is this a feasible fault? What other mechanisms might there be? 

Reply
  • Thank you all for the information. There seem to be multiple problems here:

    Failure of the 12V system so that the steering cannot be unlocked. This seems to apply to IC vehicles as well but shouldn't normaly happen when underway, only after a full stop and locking of the car.

    Failure of the 12V system so that the handbrake or parking lock cannot be released. This would also apply to IC vehicles but again shouldn't happen when underway but maybe if stopped in a queue. There appear to be manual release options but most people do not know about them.

    Failure of the EV traction system so the vehicle is hard to move/imobilised. This would be dependant on the individual system. Putting a short circuit accross a PM motor will make it hard to rotate but is this a feasible fault? What other mechanisms might there be? 

Children
  • Hi Roger,

    A short across the motor is very unlikely but the transistors in the inverter (motor drive) can fail 'on' so can cause a short. It is more likely that there is some load on the DC bus like the heaters, air con or DC-DC converter which will cause the motor to be hard to rotate.

    Regards
    Pete