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No more brakes for cars of the future:
Electric cars of the future could be able to ditch conventional brake technology in favour of powerful regeneration by battery-powered motors.
[...] Electric cars already use a combination of conventional friction braking and brake regeneration. The latter slows down vehicles using resistance from the same electric motor that propels the car, feeding that energy into the car's battery to extend its range.
DS, Citroen's luxury arm, said it is "exploring whether regenerative braking alone could eventually be the sole method to slow cars down, helping to better recharge the battery in the process, and doing away with conventional brake discs and pads".
[...] [Conventional brake pads and drums] produce "brake dust", fine particles of metallic material that separates from the pad and disc as part of the braking process.
[...] Dr Asma Beji, a non-exhaust particles expert, said in June 2021 that "the impact on health of brake wear particles is undeniable and cannot be neglected".
[...] Environmental researcher Dr Liza Selley, published a paper for the MRC Centre for Environment and Health at King's College London and Imperial College London in 2020 that suggested "diesel fumes and brake dust appear to be as bad as each other in terms of toxicity in macrophages".
[...] "Macrophages protect the lung from microbes and infections and regulate inflammation, but we found that when they're exposed to brake dust they can no longer take up bacteria.
"Worryingly, this means that brake dust could be contributing to what I call 'London throat' – the constant froggy feeling and string of coughs and colds that city dwellers endure – and more serious infections like pneumonia or bronchitis which we already know to be influenced by diesel exhaust exposure."
DS and other manufacturers including Jaguar and Porsche participate in Formula E electric car racing. The series will eliminate rear disc brakes from its next-generation machines in a bid to improve real-world research into the performance potential of purely regenerative braking.
(Score: 2) by Immerman on Thursday May 12 2022, @10:19PM
I believe the maximum deceleration torque possible from a motor is generally achieved by applying maximum power to the motor in reverse.
My motor-physics knowledge has faded greatly, but my gut says that shorting the terminals of a DC permanent magnet motor would provide braking force, since you're inducing current in the windings that will resist the changing magnetic field (akin to the way a magnet dropping through a copper pipe in slow motion. But not nearly as much as actively powering that resistance. (akin to firing a railgun upwards, to overextend )
However, if I recall correctly many (most?) modern car motors are actually computer-controlled multi-phase AC motors that contain no permanent magnets, which can be considerably more efficient (as well as being considerably cheaper since they don't require any expensive rare earths for high-strength permanent magnets.)
The efficiency gains are in part because without permanent magnets there are none of those induced "braking" currents when coasting.