Comment by traceroute66 | Hacker News Reader

Comment by traceroute66 | Hacker News Reader

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> How did you have regenerative braking on a non-electric BMW 5?

Just because the EV-brigade gave it a fancy name doesn't mean they invented it. ;-)

The non-electric synonym to regenerative braking is the combined effects of engine braking and/or tyre friction.

I frequently use it myself, for example when I'm approaching a known reduction in speed limit and its safe to do so (in the context of traffic distance behind me) I will disable the cruise control and let the car slow itself down in a relatively short distance.

After a short while you can do that sufficiently accurately so you reach the exact speed limit by the time you reach the sign post.

EV's basically do the same thing. The "regenerative" part is a bit overhyped IMHO it won't magically recharge your battery, maybe add 5–10% over the course of hours if you're lucky with the electron gods. The laws of physics still apply in an EV, unfortunatley.

Yes you might try to argue that EV regenerative braking slows you down faster. But the more aggressive nature is a double-edged sword ... aggressive slowing down with close following traffic, for example, is a recipe for easily avoidable disaster.

Just because the EV-brigade gave it a fancy name doesn't mean they invented it.

What you describe isn't regenerative braking by any stretch of the definition. Just because one considers "regenerative" to by hype doesn't mean one gets to use the word incorrectly. I guess the flip side of "pedantic" is using a word incorrectly even when one knows it's being used incorrectly.

Interesting; I thought the term referred to the fact that electricity is being generated in the process. This appears to be the DOE's definition also. [1] I'd be curious to see how it was used before this, like you say!

1: https://www.energy.gov/energysaver/how-regenerative-brakes-w...

> I thought the term referred to the fact that electricity is being generated in the process.

If we are being pedantic about it, yes, you are right in your thoughts and certainly that is what the EV manufacturers want you to think via their marketing.

But the reality is I guess you could say 95% of the "benefit" of regenerative braking is the braking side of things (and so therefore similar to the non-EV equivalent).

There is, without argument, the remaining 5% "benefit" of the generation of electricity. But certainly in my own experience of driving EVs for both long road-trips and short journeys is that the electricity generation is largely manufacturer hype. Why ? Because basic physics dictates that you're playing a net-net zero-sum game ... i.e. what you "generate" you then loose when you next stop at the lights and accelerate again, or when you next overtake a car on the highway or, or, or .... so in the end you might end up with perhaps a 5–10% net gain if you're lucky which isn't really all that much to sing and dance about.

Can you explain what the word "regenerative" means in the context of an ICE vehicle decelerating? Your description above doesn't indicate that anything is being generated.

You indicate that the generative impact seems trivial, but this is not the case for me. In my PHEV, I get an additional mile of range when I brake regeneratively getting off the freeway. This is non-trivial in a vehicle that only offers about 12 miles of EV range. It's one of the reasons that my average MPG hovers between 90 and 100.

> If we are being pedantic about it

It's not pedantry; you're just taking two roughly analogous things and acting like they have no differences. It IS relevant that EVs call it "regenerative braking" because it does "magically recharge the battery".

> that is what the EV manufacturers want you to think via their marketing.

And yet we're in a thread for an article from the U.S. Department of Energy, not a car manufacturer.

> Because basic physics dictates that you're playing a net-net zero-sum game ... i.e. what you "generate" you then loose when you next stop at the lights and accelerate again

You're missing the point entirely. The point of regenerative braking isn't that it's more efficient than maintaining a constant speed the whole time. It's that it reclaims energy when you would have to stop anyway, traditionally with the brake. i.e. city-driving when you hit stop lights.

A 5-10% net gain is an incredible benefit; I don't know why you're downplaying it. If I could make a 10% improvement to my fuel economy solely by coming to a gentle stop (which I already do anyway) it would be amazing.

> You're missing the point entirely.

No I'm not. I retain my argument that it is a zero-sum game.

The manufacturers would have you believe it's a one-way gain and you can magically recharge to 80% again through regenerative braking, but in the end it almost entirely nets out. So a lot of it is marketing fluff.

That's the point.

> If I could make a 10% improvement to my fuel economy solely by coming to a gentle stop (which I already do anyway) it would be amazing.

For all you know, you probably do.

Its just that your ICE doesn't have some fancy display pumping out the numbers to make you feel all cozy about it.

Why do you think haulage companies spend an inordinate amount of time and money on driver training beyond the obvious parts of the training ? Because driving style can affect fuel economy, sometimes substantially.

Opening my thesaurus: what do you regain/recoup when you use regenerative braking on an internal combustion vehicle? If the answer is "nothing," that's just decelerating or "engine braking" in my opinion.

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