Cell sucker?

[shankus]

I feel stupid posing this question, as I think it might be like discussing a free-energy device, or perpetual motion.

Probably like most of you, I dislike throwing away cells when I know theres some power left in them.

So, I was thinking, would it be possible to design a circuit the could suck all, or almost all of a cell's remaining capacity out, and store it in a larger battery?For instance, a circuit using a lead-acid battery, to recoup power, that may be used to charge other cells, or run equipment on what would otherwise be thrown away power.

It seems that it would require boosting the voltage to a level that could charge the larger battery, but then, there would be losses in the boost circuit that might completely null any effort to get it out.
Is there some cutoff point, for instance 1 V on a 1.5V cell, where any voltage above that point could be resonably extracted? The Opelec, for one, depletes a cell to 0.8V, right? And it is often said than an Arc AAA, CMG Infinity or Opalec can use cells otherwise useless in other equipment.
Couldn't that thought be carried into this application?

Think of this: Do they supply cells for equipment where you work? All those people turn in or throw away those "dead" cells. Or maybe the situation is even worse. Since the company is paying, perhaps they change the cells more often than needed, because it's not their nickel.

Does what I'm saying make sense? How far off-base am I? Is a charging (or more appropriately, discharging) circuit like this possible?

Am I a visionary, or a chowderhead?

 

[zmoz]

I'm sure it's possible...but why? The batteries could have what...1 watt in them? That much electricity would cost about 1/100th of a cent to just plug it in.

 

[FalconFX]

I think when you get down to that low of a voltage/current remaining for a cell, it's pretty much useless to try to draw out the remaining current. You might actually get a reverse current, unless you make some sort of inducer, in which case, you'd probably lose more energy trying to draw out the last drip of wattage out of a cell than you would be able to save out of the whole process...

 

[tonyb]

ENTROPY

 

[PaulW]

Your questions is not at all stupid. I feel the same way about tossing a battery that may have a little juice left. I paid for it. I want to use it.

The only practical way I know is for as many of my flashlights to be regulated as possible. When my arc LS battery dies, I replace the battery with one from a box of used batteries from my non-regulated lights. The disadvantage is that I don't get a full two hours on the Arc, but the advantage is that my other lights have fresher batteries. And, each one gets sucked pretty well.

But a really good cell sucker is the SF A2. I look forward to getting one. And I look forward to the introduction of 9 volt regulated flashlights from Surefire. (No, I don't know secrets -- just a nagging hope.)

 

[Lurker]

I hate throwing away power, also, but by using rechargeable batteries I have lost that feeling completely. I am no longer throwing away power or the cylinders that it comes in.

 

[Doug Owen]

The Scotts (or whatever) blood in many of us revolts at wasting energy.

While it's understood to not be practical, this simply makes it all the more important part of CGF Doctrine..... Understanding it's something deep in the genes, something no known 12 step program addresses, it should come as no surprise at all some other guy was down this path before. Lucky for us, he left at trail....

Do a web search on 'Joule Thief'. You get <http://www.emanator.demon.co.uk/bigclive/joule.htm>, from a fun Brit that did a couple of versions for just the pure joy of wringing out the last drops..... Fun read as well. Neat language, that British, kinda like English......

Doug Owen

 

[zmoz]

If you were actually able to make something like this and store it into any kind of rechargeable battery, the juice you would put in would probably be less than the self disharge rate of the battery.

 

[Blikbok]

Question: aren't completly dead batteries safer to dispose of? That might be a different advantage.

 

[PsycoBob[Q2]]

I know that military SO4-based lithium batteries are safer to dispose of when discharged. I don't really know if that's due to the risk iof shorting something with a pair of D-cell sized 3.6v lithiums, or the chemical hazard.

As for sucking the lasdt drop of juice out... unless you like in the back woods, and dislike solar, it's be cheaper to plug the Lead-acid battery into a wall-charger.

Ok, a Duracell D discharged at 0.25w will give about 18Wh of energy by the time it hits 0.9v. The US average per KWh was 8.16 cents, as of 17FEB03. At $0.50 a cell (that's low, unless you got a real good deal) you pay about 2777 cents/KWh. If I give the battery-suckers the benefit of the doubt, and assume that cell has another 18Wh in it, that's still more than $13.88/KWh. And people wonder why rechargeables look so attractive- even losing 90% of the juice from the wall (wall-wart transformer, charger, battery self-discharge, etc) it's still a great deal.


Sources: http://www.duracell.com/oem/Pdf/MN1300.pdf
http://www.ifmaenergynet.org/docs/maine_deregulation.htm

Someone, PLEASE check my math- it's late, and my brain's fried, so I'd love to find out if I got that right. I tried to be pessimistic with my estimates (in favor of the Battery-Vampires).

Assuming I got the math right, it'd be a bit expenive (in components and batteries), for little gain. Just what Flashaholics specialize in! /ubbthreads/images/graemlins/poke2.gif

I DO know of certain uses for 'discharged' cells. The Army's Laser-tag stuff (MILES gear) is interesting. SOme vehicle sets use 2 6v lantern batteries, and if the pack voltage drops below a set figure, it counts as a kill. Consequently, batteries tend to be replaced on a specific schedule, so they don't have that problem. They work great for other uses (like running a fluorescent lantern) and some places let personell borrow the cells to use them, as long as they get handed back over for accounting and disposal. If anyone's company does this, you could try powering your stuff off the 'trash' batteries.