Is this actually an ultracapacitor?

discharging

think

Electronics

time,

known

system

solvable

the

whatever

of

physics.

That was solved for I not for V.

?-)

Might be interesting to charge at low voltage (available) and discharge at a higher voltage (usable)........

Claims to have compensated at a 35W / 6A dischage rate, mechanically.

RL

So Bakhoum has designed an ultracapacitor that maintains a near- constant voltage without a DC-DC converter. The ultracapacitor is fitted with an electromechanical system that can slowly lift the core of the device out of the electrolyte solution as the stored charged is released. As the electrolyte drains away, the device can hold less charge, thus lowering, its capacitance. Since the voltage of the capacitor is related to the ratio of the stored charge to the capacitance, the system maintains a steady voltage as charge is siphoned off.

Bakhoum built and tested a prototype of the new ultracapacitor. After attaching a 35-watt load to the device, he found he could successfully program the voltage to stay within a 4.9 to 4.6 volt range. Testing also showed that the constant-voltage mechanism operates with a 99 percent efficiency or higher. The lifetime of the electromechanical motor is expected to be about the same as the lifetime of the ultracapacitor's core, Bakhoum writes.

... Also, I'm reminded of playing with my Eico 377 signal generator (classic Wien bridge, dual air variable cap). On the lowest frequency band, it's kind of unstable (it's working with ~10M resistors!), and has a long time constant, so it's easy to make it 'bounce'. Set it for a low frequency and wait for it to stabilize, then yank the dial up to a high frequency.. the waveform overshoots, rebounds and stabilizes. Or dial it up slowly, and the amplitude tracks higher than normal until you stop.

If drive power is supplied by the stored electricity, then it's just a capacitive transformer -- nothing wrong with that, and saves the difficulty of a wide range electrical converter.

Tim

-- Deep Friar: a very philosophical monk. Website:

So Bakhoum has designed an ultracapacitor that maintains a near- constant voltage without a DC-DC converter. The ultracapacitor is fitted with an electromechanical system that can slowly lift the core of the device out of the electrolyte solution as the stored charged is released. As the electrolyte drains away, the device can hold less charge, thus lowering, its capacitance. Since the voltage of the capacitor is related to the ratio of the stored charge to the capacitance, the system maintains a steady voltage as charge is siphoned off.

Bakhoum built and tested a prototype of the new ultracapacitor. After attaching a 35-watt load to the device, he found he could successfully program the voltage to stay within a 4.9 to 4.6 volt range. Testing also showed that the constant-voltage mechanism operates with a 99 percent efficiency or higher. The lifetime of the electromechanical motor is expected to be about the same as the lifetime of the ultracapacitor's core, Bakhoum writes.

I can't believe you've never worked with op-amp differentiators and integrators ;-)

Huh?

For the fanciful case of V constant, Vo...

I = d/dt(C*Vo) = Vo*dC/dt

So you can derive the dC/dt required to maintain Vo for a given I. ...Jim Thompson

I didn't explain well enough... I meant with C changing.

I _have_ had some electromechanical (L) situations with everything variable... like solenoids for instance. ...Jim Thompson

When we deal with changing C, it's more likely to be with frequency control (varactors and things), and it's more usual to work in the frequency (jw) domain, or s domain then.

Time domain stuff with varying C isn't that common in the electronics field.

Injector drivers? Pin drivers?

I take C(V) into account with DC power supplies (ceramic capacitors). ;-)

Update: I talked to the cap guy again--he says they're getting close to 50F/cm^3.

So, a 25KWHr pack (enough to run my car ~150 miles @ 70MPH) would occupy 225L. That's a 61cm cube, a large suitcase.

An electric car with this power source would be considerably lighter than mine; more streamlined cars could up that range considerably.

Interesting.

-- Cheers, James Arthur

be

ely

Green energy.

On 29/07/12 04.38, snipped-for-privacy@yahoo.com wrote: ...

Thanks for the update.

That sound very interesting - and no lithium is needed I assume.

Glenn

Right. Aerogel is just carbon. The cap's light, good for zillions of cycles, and doesn't need any exotic materials.

A lighter, electric version of my Acura could reasonably go 200mi on a charge, with no technology risk beyond the supercap itself.

I'd go for that. (I'd want to add an auxiliary gas-generator as a "spare tank"). I'd want about 10-15KW continuous (mechanical) from the power train, maybe 5x peak, and that's it. That should be light, torque-y, efficient.

(*)(Of course it's pie-in-the-sky until then. This guy was pretty insistent. He says a team at UCLA is hot on his heels, too. We'll see.)

-- Cheers, James Arthur

Excellent. And, it's greenhorn season.

-- Cheers, James Arthur

Here's an update from the UCLA team:

They make the graphene(*) electrodes with a LightScribe DVD burner.

(*) fancier than aerogel, apparently.

-- Cheers, James Arthur

Glenn wrote in news:5014f5f7$0$281$14726298 @news.sunsite.dk:

Does anybody know what happens when such a battery is crushed in an accident?? I wonder how big the fireball is going to be. And how high the temperature . My guessometer predicts the equivalence of several kilo's of TNT.

A bit off-topic, but your original post included the following lines in it's header:

Newsgroups: sci.electronics.design,sci.electronics.components Followup-To: sci.electronics.components

Two attempts to respond on s.e.d., 12 hours apart, seemed to disappear, but were found later as virtual nonsequiturs on sci.electronics.components. The sent items were addressed to s.e.c. only, as the header instructed..........

To get this reply through on s.e.d., I've had to manually edit the target in my news editor........

Was prepared to blame the news server again.

RL

Likely worse than equivalent amount of gasoline.