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A scientific accident that could change the world

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Re: A scientific accident that could change the world

#71

Post by speleding »

revelation wrote: post #48
gizmo686 wrote: post #32

Earlier quoted context omitted.

In my experience, the reason people are obssessed with battery life is that when it runs out (which it does), then you are pretty much screwed until you can plug it in for the night. I think that vendors could easily sell devices with a smaller capacity if they can charge in seconds. This seems like a benefit that is very clear, easy to explain, and understandable to a typical consumer, and it provides a near perfect…

I think the vendors could already charge the batteries faster. A Tesla supercharger charges 40/85kWh in LiIon battery capacity in 30 minutes (from empty, it gets harder to push charge in as they get full). They use off the shelf batteries. But the dirty little secret is of course that it's not necessary. You need one day of battery life, then people get home and charge it by their nightstand. Similar with the Tesla,…

The high current needed for fast charging requires thick connector wires and produces a lot of heat in the battery, and also in other components of the power circuitry. The heat is the limiting factor in the charging speed for phones.

Re: A scientific accident that could change the world

#72

Post by AndrewDucker »

Selfcommit wrote: post #68
MichaelApproved wrote: post #47

Earlier quoted context omitted.

This comment feels like its one step away from just being the word "repost". I really like browsing reddit but please leave these types of comments there. Hacker News is not reddit.

Yeah, I don't understand the down votes honestly. We've seen this - not just a few months ago. Why is it ok to post again? Should I have provided the HN link?

It's more that your comment didn't add anything to the conversation.

If you'd said "You can find the previous conversation at XXX" then you'd be contributing. As it is you just added noise.

Re: A scientific accident that could change the world

#73

Post by rbanffy »

brokenparser wrote: post #13
dmethvin wrote: post #6

Earlier quoted context omitted.

In the comments they mention about 1/4 the energy density of a lithium ion battery, so yes they don't compete on that measure. But full charging can happen in a minute or two, and you could top up a charge in seconds. Perhaps public areas would have inductive chargers on the wall; you'd just walk over and hold your phone or tablet up to it for a few seconds. Airline tray tables could have an inductive charger built i…

Your inductive charging tray tables are terrible for my magnetic tapes and floppy disks. Also, where does it get its energy from? It's much more efficient to walk around with wearable solar panels or to embed them directly into the devices. It may not work well on the north pole half the time but batteries aren't very conductive in those environments, anyway.

Guess we're not going to be able to work with our SX-64 portables on planes anymore.

Re: A scientific accident that could change the world

#74

Post by podperson »

alexjeffrey wrote: post #14
podperson wrote: post #11

Earlier quoted context omitted.

Countries with poor infrastructure and handy sources of insanely high wattage power who can afford $50,000 sedans? Which countries would those be?

I'd hardly equate lack of abundant electric car chargers with poor infrastructure. The example I was thinking of is the UK where I live, where electric cars aren't as common as in SF or the east coast. note, I didn't downvote your comment.

Fair enough but the basic point stands - a fast charging facility would be harder to set up than a Tesla "supercharger" (it would, in essence, need to use capacitors to provide the necessary power and would be limited by its available power.

Re: A scientific accident that could change the world

#75

Post by dj-doppelganger »

Hi - 1st post on Haker news. Please be nice :)

Aren't debates over energy density of super conductors v. Li-Ion batteries missing the important point, relative cost?

E.g. If the energy density is 1/4 lower but the cost is 1/40th as much then electric cars get ALOT more viable. Can anyone guess at the relative cost?

Re: A scientific accident that could change the world

#76

Post by wyager »

clebio wrote: post #36
ratsbane wrote: post #7

Am I the only one to think "hey, I could try this at home?" 1) prepare carbon slurry 2) pour on dvd 3) etch with LightScribe DVD drive... 4) Peel of graphene layer ...? I wonder what, exactly, goes into the carbon slurry and if it's necessary to etch a particular pattern with the LightScribe.

I wondered about the etching process too. It might not be at all like a normal R/W pattern for a DVD. They could conceivably be scanning radially, or using a very slow revolution, or (is this possible?) re-tuning the beam's frequency. Not insurmountable, but might require low-level re-writing of the driver, depending.

>(is this possible?) re-tuning the beam's frequency.

No. DVD burners simply use a 630nm or 650nm red laser diode. It can not be re-tuned more than a few nm, by regulating the temperature of the diode.

You could replace the diode, but that is more effort than it's worth, and there's not much else to replace it with. If you wanted more power you might use a different diode, but the diodes are almost always buried really far in there and you would have to replace the electronics as well.

Re: A scientific accident that could change the world

#77

Post by solistice »

BenoitEssiambre wrote: post #4

Conspicuously missing is any mention of energy density. Who cares about power density. That's juste how fast it can discharge. We don't need capacitors that can discharge faster. All capacitors are already much better than batteries with respect to power. We need capacitors that can store more energy. Capacitors typically suck at that and this article doesn't give any indication that these new ones are better.

I have the article printed out somewhere, the energy density is in there, about 10 times that of conventional activated carbon supercapacitors and 3 times that of a comparable thin film lithium polymer battery off the top of my head, but I could be wrong. You can find the original paper at the AAAS (American Association for Advancement of Science) website, but its behind a registration wall, and they do mad data mining, so registering might take a while. Also, I have to remind you that this is an article on io9, not in the Scientific American. There are several other articles about this which likely came prior to io9 picking up on the story, and im pretty sure they provide some additional numbers which you so or so will find in the original paper on the subject. Here's the Kady paper that is referred to by the way. http://www.sciencemag.org/content/335/6074/1326.abstract

Re: A scientific accident that could change the world

#78

Post by TylerE »

whitewhim wrote: post #52
ratsbane wrote: post #7

Am I the only one to think "hey, I could try this at home?" 1) prepare carbon slurry 2) pour on dvd 3) etch with LightScribe DVD drive... 4) Peel of graphene layer ...? I wonder what, exactly, goes into the carbon slurry and if it's necessary to etch a particular pattern with the LightScribe.

After reading several papers on this I think that the hardest issue would depositing the GO and electrolytic layers on a CD substrate. Although there are some fairly reliable and not terribly difficult methods I doubt many would have the materials at home. I would love to try this but I'm a poor student. I may see if I can locate some GO onthe chem labs this summer when no ones around.

It's graphene, especially tiny bits of it, a bit of a biohazard also? (Think asbestos)

Re: A scientific accident that could change the world

#79

Post by gallerytungsten »

mbell wrote: post #64
ScottBurson wrote: post #62

Earlier quoted context omitted.

Charging capacitors is normally much more than 90% efficient. They're not like batteries, where a chemical reaction occurs during charging. Resistive losses in capacitors are normally negligible. In this case they will probably still be negligible, I'd guess, because of the high conductivity of graphene.

True but you've got to consider the numbers we're looking at here. As an example an iPhone 5 has a 5.45Wh battery, if you wanted to replace that with a super-cap and charge it to 5V in 20 seconds you'd need to provide ~1000W of power or 200A @ 5V. Even if the super cap had very low ESR, call it 1mOhm, which is extremely low compared to current super-caps, you'd still end up dissipating 40W as heat with ~96% efficienc…

Perhaps phone makers can start making their cases out of aluminum, with enough mass to take the heat. 40W over 20 seconds doesn't sound too daunting.

If you split such an aluminum backplate into two parts you could use them as the power contacts. Then you could have a "coffin" type charger where you put in the phone, then closed a cover to run the charge cycle. Kind of like the cover of a washing machine, to reduce the danger level.

Re: A scientific accident that could change the world

#80

Post by rcamera »

ratsbane wrote: post #7

Am I the only one to think "hey, I could try this at home?" 1) prepare carbon slurry 2) pour on dvd 3) etch with LightScribe DVD drive... 4) Peel of graphene layer ...? I wonder what, exactly, goes into the carbon slurry and if it's necessary to etch a particular pattern with the LightScribe.

The professors who found this actually wrote a paper [1] explaining every step that they did to create their supercapacitor, including the formula for the gel-like electrolyte they used. The biggest problem I've found to making this at home is getting graphite oxide. They are expensive on the net (google it, not linking any store because I don't know any trustworthy), or hard to make (the usual method requires strong oxiders like sulfuric acid) [2]. There is a bottom-up approach to making them, that uses glucose [3], but I have no idea how hard it is, I need help from someone more knowledgeable in Chemistry before I try it. So if you want to really try this out, read those papers.

[1] http://www.sciencemag.org/content/335/6074/1326.abstract [2] https://en.wikipedia.org/wiki/Graphene_oxide [3] http://pubs.rsc.org/en/Content/ArticleLanding/2012/JM/c2jm15...

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