Comment by devy | Hacker News Reader

Comment by devy | Hacker News Reader

Parent Full thread

How did they achieve the impressive 40-percent improvement in EV range?

        "Like mass, which comes off by the tenth of a gram," say Tim Grewe, 
	Chevy's general director of electrification, "range goes up with every detail. 
	Our motors are more efficient, our battery discharge is more efficient, 
	our inverter efficiency is higher and our drive-unit spin losses lower. 
	Yet we also improved [the] fun-to-drive [aspect], with 30-percent better 
	launch and low-end acceleration, because that's a very pleasing feel."

In a nutshell, EV range is all about energy efficiency because current battery energy density is a few orders of magnitude less than fossil fuels and efficiency matters a lot with all things considered when energy capacity is given.

And Germans know this much better. It's why BMW custom developed an brand new chassis and majority of the components being used in BMW i3 with super lightweight but much sturdier carbon fiber reenforced plastic body[1] and other designs to achieve that goal whereas GM uses steels and traditional materials for Volt. Similarly by contrast, GM uses existing vehicle platform to cut down cost[2] instead of custom design one for Chevy Volt.

The end results of BMW's effort are very self-explanatory: BMW i3 with 124 MPGe is THE MOST ENERGY EFFICIENT [3] vehicle of all vehicles rated by US EPA in all classes in the United States for 3 years straight. On the other hand, GM Chevy Volt's 98 MPGe is ranked far behind.

[1]: https://en.wikipedia.org/wiki/BMW_i3#cite_note-BMW0410-15

[2]: https://en.wikipedia.org/wiki/Chevrolet_Volt#Second_generati...

[3]: https://www.fueleconomy.gov/feg/best-worst.shtml

Full disclosure: I had owned BMW ActiveE (an engineering prototype comparable to Volt in terms retro-fitting EV components into existing ICE car platform (BMW 1-series) with traditional material being used.) and have driven BMW i3 since ActiveE's retirement in their field trial.

And one costs about $10,000 more (approximately 25% more than the price of the Volt, a rather large difference to most people). And considering it's a BMW, you pay extra for a steering wheel, brakes, etc. (that's sarcasm, but really, BMW is one of the brands that's great at nickel and diming their customers, and don't forget about long term cost of a vehicle, much more expensive to fix a BMW than a Chevy. I know this because I have one of each, non-electrics)

So yes, it may be better because of the carbon fiber infused paneling, but you're paying for that. To ignore the price of automobiles when comparing them, is simply ridiculous (you're not the only who has done this devy, so this criticism is not pointed specifically at you.)

Also, to emphasize, when a cheap aluminum, steel or fiberglass part breaks/is wrecked, it's cheaper to replace than a carbon infused panel. Try to re-bend the frame of a steel car (rather easy) and re-bend the frame of a car with a monocoque body made of carbon fiber (You can't).

How a car is designed is not solely about the efficiency of it's drive train, but rather there are a large number of constraints on the automobile. How large is it? How many passengers and cargo can fit? How comfortable is it? Does it have all the nice features that modern consumers want? Does it have more than one cup holder (BMW is notorious for failing this test, an interesting cultural difference between US and German automakers) How does it do in safety tests? How does it look? Etc. etc. And again, one of the most important: How much does it cost?

> Also, to emphasize, when a cheap aluminum, steel or fiberglass part breaks/is wrecked, it's cheaper to replace than a carbon infused panel. Try to re-bend the frame of a steel car (rather easy) and re-bend the frame of a car with a monocoque body made of carbon fiber (You can't).

Can you repair the more exotic steels that are now used on cars? I was in an accident a year ago, and all of the affected ultra-high strength steel members of the car had to be directly replaced: it was explained to me that they cannot be straightened or welded.

As to the CFRP used in the BMWs, it is actually "repair friendly". The insurance costs of a BMW i3 are no more than other comparable luxury cars: in an accident, they cut out the affected portions of the CFRP and epoxy replacement elements in place. The material costs might be slightly higher, but the labor costs are lower.

Reply on news.ycombinator.com