efficiency of regenerative braking?

You have to account for the efficiency losses during acceleration, too. The controllers lose some as heat, the motors lose more, then there's tires, gearing, and so on. Probably wouldn't get more than 15 mph out of it.

Dan

wrote in message = news: snipped-for-privacy@73g2000cwn.googlegroups.com... |=20 | snipped-for-privacy@my-deja.com wrote: | > Something to keep in mind is the energy of a moving vehicle is | > proportional to the square of its velocity. So a car doing 30 mph = with | > a 50% recovery system could get back up to about 21 mph on the | > recovered energy. Shows how it can make a big difference in stop = and | > go city driving. |=20 | You have to account for the efficiency losses during acceleration, | too. The controllers lose some as heat, the motors lose more, then | there's tires, gearing, and so on. Probably wouldn't get more than 15 | mph out of it. |=20 Dan

Assuming the two (2) orders of magnitude more weight/energy ain't an issue.

Bret Cahill

"Sorcerer" ha scritto nel messaggio news:gqzhh.95834$ snipped-for-privacy@fe2.news.blueyonder.co.uk...

This last one doc is quite intersting.Energy density is not that high in the order of 100 Wh per kg (vs > 150 Wh/kg of lithium),but it's still useful in electric vehicles.Moreover,number of cycles efficiencies are better and use no hazard chemical (although lithium is not so dangerous or polluting)

"Alessio" wrote in message = news:4586d56d$0$19104$ snipped-for-privacy@reader4.news.tin.it... |=20 | "Sorcerer" ha scritto nel messaggio | news:gqzhh.95834$ snipped-for-privacy@fe2.news.blueyonder.co.uk... |=20 | >

|=20 | This last one doc is quite intersting.Energy density is not that high = in the | order of 100 Wh per kg (vs > 150 Wh/kg of lithium),but it's still = useful in | electric vehicles.Moreover,number of cycles efficiencies are better = and use | no hazard chemical (although lithium is not so dangerous or polluting) |=20 Yes, once we get past the popular press and the nay-sayers there is much that is left unexplored in energy conservation.

The best capacitor would need to weigh a few hundred pounds even for a small car. Because of the other inefficiencies, i. e., generating the electricity, regenerative braking would always be a net loss with capacitor energy storage, even on flat land, even braking and accellerating every half mile.

Even if a "super cap" was developed the prospect of a short near a lot of Li ion batteries . . .

A couple years ago some nut job was trying to get government funding for a "super cap" to power an EV w/o batteries.

He was widely ridiculed. Some were posting stuff like the cap equivalent to 15 gallons of gas would weigh 100 tons.

Finally I inquired as to the size of the crater a fully charged "super cap" would leave in the road from a short, assuming a super cap could be developed. A poster calculated it would be equivalent to several hundred pounds of TNT if it didn't discharge so much faster than the TNT reaction. The crater would be at least 30' in diameter.

I haven't heard a peep about cap power since.

Bret Cahill

Who said anything about a car that couldn't do hills or busy roads? The car could still do them, and would still have regenerative braking using batteries. It would just be a bit less efficient at recovering energy under some circumstances, which do not apply for many users. Ever been out to the plains states? There are huge parts of the earth that are flat and are not built up enough to have stop and go traffic.

While capacitors may work better than batteries for stop and go traffic or small hills you are not going to store enough energy in any reasonable package to be able to climb a moutain pass through the rockies. And they will not be able to store all the energy from the trip down the other side.

I was poking fun at your restatement of the obvious. The main purpose of regenerative braking is to recover energy to extend the range of the car. I even gave an example of getting back up to a certain speed using the energy recovered. For you to the come out with, "The also help supply power for acceleration too AIUI." was just too funny.

The losses during acceleration were figured in. I had previously written,

"Figure the motor/generator itself is 90% to 95% efficient. That would

mean that you would lose 5 to 10% putting the energy into storage, then

another 5 to 10% converting it back to mechanical energy. If the battery pack is used to store the energy, it has internal resistance so

some of the energy is lost as heat. Batteries are not very efficient for rapid charge and discharge cycles. As a guess let's say you get

60% of what you put in back out, with the remainder going to heat. So you could be looking at 90%*90%*60%=48.6% "

Using average rather than low end numbers the above would be

92.5%*92.5%*60%=51.3%

The 90% to 95% efficiency includes losses in the controller. These motor/generators are well proven out in industrial machinery. No need to reinvent the wheel for automotive use.

You're talking total bollocks.

Do you just make this stuff up ? It sounds like it for sure.

Graham

And what's the use of car you can only viably use there

Graham

You clearly don't know much about the effect on batteries of high charge and discharge rates.

Your display your ignorance admirably well.

Graham

In principle it's 100%, since that's the only reason stationary bicycles. and Gold's Gym works.

In practice, it depends more on battery cable gauge than physics,

Replace the RPM's with RPS's. Since the only cranks who even use RPMs is GM & Asswipes Inc,

No they don't. Varible Frequency networks are usually called servo motors, Which are as often as not these days, being replaced the computers, rather than electrical systems. Wide area power distriubtion genarators don't even work unless you have them synchronised to about 60Hz +/- 0.1 Hz,

What is a google?

-- Rich

Google it and find out....

See:

Make that "large currents for a very short time, much shorter than the

4 seconds it takes for a Tesla to get to 60 mph."

In other words, the energy density is 2 orders of magnitude less than a battery.

You know the energy density of a "super cap?"

Bret Cahill

We're still waiting for you to compare the energy density of the best capacitors to batteries.

Bret Cahill