Comment by sawjet

7 years ago

It will ultimately be limited by it's cooling, as all Teslas have been. Can it manage long, steep grades while towing? Downhill, ICE motors can be driven by the wheels to preserve both fuel and brakes.

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sawjet

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kube-system  7 years ago

If regenerative braking is good enough technology for trains, it ought to be good enough of a technology for a light truck.

https://en.m.wikipedia.org/wiki/Dynamic_braking

  • arghwhat  7 years ago

    Note that trains are a very different scenario due to not being battery powered.

    Many (most?) trains dump excess charge into the grid, meaning that it has no limitations on brake power nor capacity.

    Battery-powered vehicles have to protect their battery, limiting brake power to keep the battery cool, and brake duration as it cannot overcharge the battery.

    To compete with a train, a battery powered vehicle would need to implement rheostatic braking (i.e. brake resistors).

    Of course, conventional engine braking is not worth comparing to any of this, but I thought it was important to emphasize that trains ≠ cars.

    • kube-system  7 years ago

      Of course there are many differences between a train and a car.

      But the technology is exactly the same: apply an electrical load to a motor/generator and it will generate a braking force. The source of the load doesn’t really make a difference as long as it meets implementation requirements.

      (Perhaps maybe the most ironic way they could dump excess electricity could be by running the onboard air compressor — literally the same thing an ICE vehicle does to dump energy when engine braking: compressing air.)

      My point is that the technology is definitely a good fit for braking large loads.

      8 replies →

arghwhat  7 years ago

Engine braking with ICE is practical, but is pretty much pointless to compare with regenerative braking capabilities of an electric motor.

Not only does regenerative braking recharge the battery, it is possible to apply entirely arbitrary reverse torque should need be, where an ICE has a pretty fixed resistance.

  • Goz3rr  7 years ago

    >where an ICE has a pretty fixed resistance.

    That's what the gearbox is for

    • arghwhat  7 years ago

      Apart from inertia on initial clutch-in, there are diminishing returns from increasing the gear ratio when it comes to compression losses.