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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?

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  • Thanks for that insight Pete.
    Well if it was my challenge, and the device substrate to body diodes were not thermally up to it then the may be some SiC schotkys in parallel, and then we let the DC bus rise as far as we dare without popping something on the generated power, and only clamp it if we cannot charge the battery or do something useful with it, whatever.

    My feeling is with a bit of extra thought the DC bus voltage could be used to fan cool  it's own emergency load dump - how much are we talking ? , a fan cooled car radiator can dump 20-30kW to air pretty much non-stop at 120C, and we could go hotter with oil cooing  (e.g. this one~  400watts per degree, so 60 degree rise ~25kW.. ).

    Mike

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  • Thanks for that insight Pete.
    Well if it was my challenge, and the device substrate to body diodes were not thermally up to it then the may be some SiC schotkys in parallel, and then we let the DC bus rise as far as we dare without popping something on the generated power, and only clamp it if we cannot charge the battery or do something useful with it, whatever.

    My feeling is with a bit of extra thought the DC bus voltage could be used to fan cool  it's own emergency load dump - how much are we talking ? , a fan cooled car radiator can dump 20-30kW to air pretty much non-stop at 120C, and we could go hotter with oil cooing  (e.g. this one~  400watts per degree, so 60 degree rise ~25kW.. ).

    Mike

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