Good gawd, Drivel was right, after all.

[Grimly Curmudgeon]

[Bill Wright]

It was claimed that it will be possible to charge a supercap in an electric car in one minute. I wonder what the current would be, and what size cables and connectors would be needed. Also I wonder what the charging station infrastructure would be.

Bill

[John Rumm]

Dribble as usual was extrapolating too far without actually thinking through the implications.

While a high capacity super cap would be good new for all sorts of electronic gadgets, it would simply bring a different problem should you apply it to (longer range) transport.

If you have a 50kWh battery and want to charge it, what charge rate do you need to use to charge it in a minute (or even ten)?

(there are actually some even more interesting developments using hybrid LiPoly batteries with carbon nano tubes to increase capacity)

[Ericp]

Second one as well. Uni of California announced they stuffed nanotubes in a lithium battery and found it lasted longer, held three times as much and charged in ten minutes.

[The Natural Philosopher]

of course its possible. The car would get about 3 miles on it though.

And imagine shorting it..

[The Natural Philosopher]

NOT to increase capacity. To decrease internal resistance. faster charging, no more miles per charge.

[The Natural Philosopher]

No,. they didn't. read the thing carefully. It had three times the POWER density, not three times the ENERGY density.

People are so easy to mislead where green things are concerned.

[Andy Burns]

3x the capacity, 10 minute charging time ... still in the research labs.

[Andy Burns]

Yes, they *are* talking about 3x energy density in milliamp hours per gram (as well as discussing charge rates in amps per gram).

[Sorry the links are images, the Nano Research journal is dumb enough to think they can charge £30 for access to their online articles while giving a free peek at the first page]

[Lobster]

They're even dumber than that actually: have a free pdf file:

[Lobster]

... oh, actually to be fair on the publisher, that's deliberately free:

"Tsinghua University Press (TUP) provides ?Just Accepted? as an optional and free service which allows authors to make their results available to the research community as soon as possible after acceptance. After a manuscript has been technically edited and formatted, it will be removed from the ?Just Accepted? Web site and published as an ASAP article."

[Brian Gaff]

I think the answer has to be 'very large'

Brian

[John Rumm]

That statement seems mutually contradictory...

Even just a reduction in internal resistance would make more of the stored energy usefully available, and result in less dissipation in the cell itself.

However what I was reading also suggested an increase in capacity as well:

[Onetap]

Where is Drivel? He hasn't been around recently. Sectioned? Dead? Recovered?

[The Natural Philosopher]

compared with carbon electrodes. But I have never seen carbon electrodes in any battery its been my misfortune to destroy.

And plenty of other people are getting better than that using other ways:

Note about twice the energy density of this 'new' research using ..air!.

Something is missing, because lets say that standard today technology is capable of say 1Ah/gm at 3.7v That's 3.7watt hours per gram, or 3.7kwh hours per kilogram, or 37kwh per 10kg. So an EXISTING car better ought to be around 10kg!! No WAY is ANY commercial lithium battery anything LIKE that.

e.g. an uncased pack of lithium cobalt technology

gets around 25watt hours in 200 grams.

so about 125 watt hours per kilogram. A factor of at least 10, possibly 37 ...different from these 'claims'

So something is not adding up.

milliampere hours per gram is not power density and its not energy density. Its current density, and something is not making sense here.

viz "At the meeting, Au said that his research group has demonstrated a coin-sized rechargeable lithium-air battery with a current density of

600 mAh/g, which is much higher than the current densities of 100 to 150 mAh/g of lithium-ion batteries.

Read more at:

"

But again, without knowing what the terminal voltage is, its impossible to know what the energy density is.

My 'what a BEV needs' boil down top at least 200Kwh in a battery weighing no more than 200kg. That should give you an all day driving sort of range. So a watt hour per gram essentially. For the complete battery.

current state of the model world batteries are achieving an eighth of that.

Nickel probably less than 1/15th of that.

The world is full of wonderful claims that are couched in terms that hide the actuality.

I have no doubt these guys have done good research, but by starting from a piss poor place and using terms that don't mean much in the real world, its hard to see that the claims amount to much.

As I said, current batteries are about 8 times worse than they need to be. Even if these are three times better, its still not good enough.

And the question remains. Three times better than what, and in what way?

is worth a read. Petrol 12,200 Wh/kg So at 30% efficiency that's still around 4Kwh per kg.

Lithium ion 130 - 1200 Wh/kg Even at 90% efficiency that's not cutting the mustard. And nowhere have I seen a 1.2Kwh/kg battery. The lower figure of around 130Wh per kg is more like what's around.

Read em all and still no answers.

[The Natural Philosopher]

Much better. Now try searching on the all important word 'voltage'

"The voltage range is set to 0.01?2.0 V"

is The ONLY mention of voltage with an actual NUMBER and hence power, and energy, at all!

needless to say 4 ampere hours per gram at 0.01 volts is not exactly a huge energy density. but 2v - 8 watt hours per gram - would have investors leaping for their chequebooks. 8 kilowatts per kilogram is an

800Kwh per tonne battery.

That's a 110bhp (average) 30 tonne truck all day!

I see no investors leaping for their chequebooks. Ergo I conclude there is something more here than meets the eye.

[The Natural Philosopher]

work on a tank of fuel being a couple of hundred kwh in electrical terms. 200kwh in 1/60th of an hours is 12MW.

So about 13,000 amps at 240V..

Of course the supercap is only enough to get you five miles.. so probably about 130 amps

realistically it should be possible to supply those sorts of peak loads at 'filling stations' but it wont be easy..or cheap.

[polygonum]

But if the recharge station itself has mega-super-caps that it charges up relatively slowly, then the delivery of power to the charging station might be very achievable.

(Can't help thinking that filling stations canopies represent a huge area desperate to be populated by solar cells. Though being built next-door to nuclear power stations would be more likely to fulfill the electricity requirement.)

[The Natural Philosopher]

Not significantly. WE get about 20% capacity loss from the 10 hour rate with models draining them in 5-10 minutes. travelling for a couple of

*hours* they are already as good as they need to be.

The key things is *recharge* losses when being banged full of electrons in a hurry. They get hot and that's where you lose power and edge up towards 'unsafe'..

realistically a safe if not especially efficient charge is 20 minutes or so on existing technology.

I've seen prototypes quotes as being safe for 5 minutes.

Boost of power is not boost of capacity.

As I said, power is not that hard. model aircraft batteries are edging towards at 3 minute discharge times something like a horsepower per pound weight, or more.

giving an overall performance level with airframe and motors stuff of around 500bhp-800bhp per tonne. Which is formula one (fuelled up) levels of performance. The problem is that its a wild ride, but it only lasts a couple of minutes.

>

[The Natural Philosopher]

Actually the way I would do it is big f*ck off mechanical converters containing loads of rotational energy.

I flew once in a research plane of Decca's. Massive rotary inverters powering the kit 'why do you not use transistorised inverters?' 'Well we tried. And when they pulled the gear up, it all stopped for 15 seconds'

:-)

Supercaps are nowhere near good enough yet. And the thing that makes em so fast charging - very low resistance - also makes them bloody dangerous. Imaging a screwdriver through a supercap with a few kwh of energy in it. You are talking serious amounts of TNT equivalent.at least a kg.

Blow your bloody doors off!