41–50 of 54 posts
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Holy crap, what can you do with kW lasers besides instantly cut almost anything?
kW isn't that high for pulsed lasers. Particularly since with Q-switching you can get very short pulses and mode-locking ridiculously short pulses. Total energy for a 1ps pulse at 100kW is negligible.
ie When I plug my phone in to charge, the super cap is "instantly" charged. Then a smart charging circuit would use the super cap to charge my battery.
Situation and my expectation: I'm headed home from work, drop off my laptop and leave for some social gathering, but my phone is about to die. Trying to charge me phone for the 1 min I'm in my house in futile. However, my expectation is that the super cap would fully charge. Then while I'm walking to my destination, it could charge my battery to some reasonable percent.
I'd be really happy even if I could get ~20% or so from the fully charged super cap. Would definitely be better than nothing.
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You can use a DC/DC to boost the voltage.
Sure. In fact you'd want to use a high-efficiency buck/boost converter to take advantage of the entire discharge curve. However you're only storing about 20% of the energy at 2.7V. Edit: I'll show my work. Farads are Joules (energy) per Volt (electric potential) squared. That means that the formula for energy stored (E) in a capacitor is E=CV^2. A 1200F cap charged to 2.7V stores 8478 Joules of energy. A 1200F cap ch…
That doesn't have to be an issue. There are high efficiency joule thief IC's that'll take a voltage input around 0.3v.
Here's her actual submission [1]. She created a novel dielectric and achieved an energy density of 20.1 Wh/kg which is about half of that of a lead-acid battery, and something like 6%-10% of a Lithium Polymer battery. She lists a capacitance per volume, but nothing about breakdown voltages, so I can't say what the size of her capacitor would theoretically be for 1200F rated at 6V. Nor can I say if it'd even be feasib…
A much cooler (but obsoleted by improving capacitor technology) was flywheel based pulsed energy: http://www.bevoware.com/research/cem/IEEE/PR%2071%20Werst%20...
And a supercapacitor will probably be what's inside to allow that.
The incredible charge rates of supercaps will someday (when the energy density improves enough) become a nice feature.
It's possible some version of LiPo batteries will improve the charge rate dramatically, but I believe the rate is limited by chemical reactions.
I think it's much better to think of a capacitor as a spring: * they store energy; * they can release energy quickly; * when put in parallel they get stronger; * when put in series they get weaker; * the RCL circuit differential equation is the same differential equation as the damped harmonic oscillator.
Earlier quoted context omitted.
Holy crap, what can you do with kW lasers besides instantly cut almost anything?
kW isn't that high for pulsed lasers. Particularly since with Q-switching you can get very short pulses and mode-locking ridiculously short pulses. Total energy for a 1ps pulse at 100kW is negligible.
Can someone remind/explain to me what happens if I were to use both my phone's current battery but put a super cap in front of it? ie When I plug my phone in to charge, the super cap is "instantly" charged. Then a smart charging circuit would use the super cap to charge my battery. Situation and my expectation: I'm headed home from work, drop off my laptop and leave for some social gathering, but my phone is about to…
It's a really bad metaphor for supercapacitors having worse energy densities than for example lithium ion batteries, and that having a supercapacitor large enough to recharge your battery to 10% would esentially entail carrying around another battery.
Honestly, if you have a phone you can actually open, you'd be better advised with an exchange battery, and if you can't open it, an external battery pack you carry around for emergencies like this.
For example, I think this external charger might do what you want it to do http://www.amazon.com/Energizer-Energi-To-Go-Battery-Operate... but your requirements might differ.
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Most supercaps are rated for very low voltages (this one is only rated for 2.4V), as dictated by the breakdown voltages of the dielectric and its manufacturing tolerances. A 6V-rated 1200F supercap made from the same materials will be considerably larger. Further, most electrical engineers will enforce a factor of safety beyond the manufacturing tolerances . This is doubly true for capacitors, since dielectric failur…
Why would you need 6v for a phone? I got feeling this was pulled out of his ass. Everything works on sub 2V there if I am not gravely wrong (not sure for the light source for the display)
http://www.amazon.com/Anker%C2%AE-1900mAh-Li-ion-Battery-Sen...