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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

#101

Post by [deleted] »

wamatt wrote: post #100
ChuckMcM wrote: post #96

Earlier quoted context omitted.

Excuse me? This from the linked article (and in the paper abstract): "These micro-supercapacitors demonstrate a power density of ~200 W cm−3, which is among the highest values achieved for any supercapacitor." Granted its not a legitimate energy density (wrong units) but lets guess it is 200 Ws per cubic centimeter. I make that guess based on the comment in the video that they ran an LED for 5 minutes. So an LED is l…

>That said, I immediately dug an old LightScribe CD recorder out of my junk bin to start playing around with making graphene sheets :-) You serious? Sounds interesting, do tell us more.

[deleted]

Re: A scientific accident that could change the world

#102

Post by lostlogin »

brokenparser wrote: post #67
lostlogin wrote: post #59

Earlier quoted context omitted.

Unfortunately both types die with exposure to magnetic fields - I accidentally too mine into an MRI scanner. This may not Oruro at a lower field strength with the chip type however.

SYNTAX ERROR UNEXPECTED TO... Oh, :s/Oruro/occur/

Wow. That was a bad one, sorry, and I can't edit it. It was supposed to say: Unfortunately both types die with exposure to magnetic fields - I accidentally took mine into an MRI scanner. This may not occur at a lower field strength with the chip-type card however.

Re: A scientific accident that could change the world

#103

Post by mbell »

AnthonyMouse wrote: post #98
mbell wrote: post #64

Earlier quoted context omitted.

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…

>200A @ 5V I don't think so. Have a look at the comparison image around 3/4ths of the way down the page here: http://www.interfacebus.com/Copper_Wire_AWG_SIze.html 14AWG (the small one) is the one rated for 20A which you might find in the power cord for a desktop PC, and is significantly bigger than the wire on your current phone charger. The big one (1/0) is rated for 125 amps. You have to go to 3/0, two sizes highe…

Your right that the way to solve the current issue is to increase voltage, but that creates a list of other problems, the most notable of which, death, you've already touched on, but here some others:

1) You likely still want USB charging support, so now you need a boost converter in the phone or cable.

2) Your PMIC needs to accept the higher input voltage, and you have to be willing to accept the reduced regulator efficiency from the increase in Vin - Vout.

3) 24V running around in a phone creates a lot of possible problems that you don't have with 3.7V cells. Increased moisture sensitivity, gradient induced oxidation, etc.

4) You still need a ton of power. If you jump to 24V then you still need ~42A to hit a 20 second charge, go to 60 seconds and you need ~327W or 13A @ 24V. That is still a massive charger with 10 gauge wiring (1 conductor is 2x + the diameter of the entire lightning cable).

Keep in mind these are lower bound numbers all around. Reality could be 50-100% higher for power needs. The ESR value I threw out above is also a very optimistic minimum hoping that this new tech has much better ESR characteristics than current super-caps which for large capacity models can be up in the hundreds of mOhms which causes a huge thermal issue.

Its still a long ways from being even remotely reasonable for super caps to replace batteries in high power devices like phones and tablets.

Re: A scientific accident that could change the world

#104

Post by lostlogin »

gus_massa wrote: post #70
lostlogin wrote: post #61

Earlier quoted context omitted.

Is that at the fuse box or the power point on the wall? Sorry if this is a silly question, it's just that here in NZ it's nowhere near that at the wall as the fuses are 10 amp ish.

The 200A are at the fuse box (in new houses, old houses may have less). The wall sockets usually have 110V-15/20A connections. But there are some especial sockets with 240V-30/50A for special applications, like clothes dryers and electric ovens.

In our old house some genius used paper clips instead of fused wire in the (very old) fuse box. Not sure how I didn't die when I draped and extension lead in a puddle and got a shock. After I recovered I looked in the fuse box to see why the fuse didn't blow and found one fat paper clip over the gap. I'm not sure what current the box took, but I'm sure glad it wasn't 200Amps.

Re: A scientific accident that could change the world

#105

Post by ChuckMcM »

wamatt wrote: post #100
ChuckMcM wrote: post #96

Earlier quoted context omitted.

Excuse me? This from the linked article (and in the paper abstract): "These micro-supercapacitors demonstrate a power density of ~200 W cm−3, which is among the highest values achieved for any supercapacitor." Granted its not a legitimate energy density (wrong units) but lets guess it is 200 Ws per cubic centimeter. I make that guess based on the comment in the video that they ran an LED for 5 minutes. So an LED is l…

>That said, I immediately dug an old LightScribe CD recorder out of my junk bin to start playing around with making graphene sheets :-) You serious? Sounds interesting, do tell us more.

Of course I am serious! Still trying to figure out what they used as a 'base' graphite oxide slurry (pencil lead in solution it isn't)

Re: A scientific accident that could change the world

#106

Post by mark-r »

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,…

> Bandaging peoples irrational fears might simply not be a very viable business model.

Are you kidding? It's one of the best business models ever.

In this case I think you have it backwards. Instant charging isn't bandaging a fear, because you rightly make the point that the fear of running out of power is already covered by ensuring the device has sufficient capacity for the worst case. Indeed it will create a new fear: forgetting or not being in a position to top off the charge when necessary.

Re: A scientific accident that could change the world

#107

Post by achy »

I wrote this last time too: Having a better conducting, higher surface area electrode is a huge step. BUT it doesn't really change the fact that a carbon based supercapacitor requires an electrolyte to form the double layer, and all existing electrolytes have a breakdown voltage below 5V. What we need is a better electrolyte. In calculating energy storage in a capacitor, the energy increases exponentially with voltage, while linearly with capacitance.

Re: A scientific accident that could change the world

#108

Post by lambdasquirrel »

ChuckMcM wrote: post #96
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.

Excuse me? This from the linked article (and in the paper abstract): "These micro-supercapacitors demonstrate a power density of ~200 W cm−3, which is among the highest values achieved for any supercapacitor." Granted its not a legitimate energy density (wrong units) but lets guess it is 200 Ws per cubic centimeter. I make that guess based on the comment in the video that they ran an LED for 5 minutes. So an LED is l…

That's still power density. Power is Watts. Total energy is joules. You haven't addressed the parent's concern. We are interested in how long it can keep up that wattage, ie. joules/sec.
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