Comment by arghwhat
7 years ago
Of course, except that normal cars have no component to dissipate the load. The battery is the only way, and it has significant limitations.
A resonable auxillary air compressor won't make a difference. With a heavy trailer going down hill, you'd need to at least dissipate tens of kilowatts, maybe even touching triple digits if you also need to slow down.
Nowhere to dissipate the power → no regenerative braking.
There’s probably a few things this truck has that normal cars don’t have.
The air compressor comment was an illustrative tougue-in-cheek comparison, not a serious suggestion.
Imagine the amount of power needed to run an air compressor with a displacement in the 5-6 liter range. That’s exactly the amount of power we’re talking about. Because that’s literally what an engine-braking truck is doing, it’s driving its engine as an air compressor.
Your “tens of thousands of watts” estimate is probably just about right. And that’s not anywhere outside the realm of doable. That’s probably well within the abilities of regenerative system in the drivetrain this vehicle will have, but even if we assume it isn’t, a 10kw resistive load is a $100-$200 part, off the shelf.
My PHEV minivan (Chrysler Pacifica) does close to 100 kW of regen in hard braking. I imagine the Cybertruck could easily double that, probably a lot more.
Peak dissipation is not particularly interesting in this context.
That current is charging the battery—not dissipation. I have no idea what kind of energy the friction brakes dissipate (that's not reported on the dash like regen braking is).
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