anyone know anything about electricity?

[Dr_Demento]

I wasn't sure where to put this, but heres the scoop.


My daughter got me one of those "no battery" flashlights for Christmas, you shake it to make it work.

It looks just like this one, but its not the same brand.
http://www.thinkgeek.com/gadgets/lights/5a9f/

I haven't messed with it since Christmas, and yesterday, I got it out of the box and thought I'd see how long it would shine before running down. It still had a charge when I turned it on, so the capacitor holds a charge really well. I shook the light maybe 20 or 30 times to make sure it was as bright as possible. Then set it down to see how long it would take to discharge. That was at 6pm yesterday.
According to what I read about these lights, it should be bright for about 20 minutes, but put out light for 2 hours.
Sassy and I went to bed at 11:00 and it was still just as bright as ever. Thats 5 hours pretty impressive huh? But wait!

I left it on, knowing full well that it would be dead by morning, but i figured I could shake it for exactly 1 minute then and see how long it lasts.
This morning we got up at 6am and it was still going, and showed NO signs of dimming. Its not a strong light to begin with mind you. It has one led bulb in it.

So it had been on 12 hours so far. I left it on when I went to work but i moved it. Last night it was about a foot away from my cell phone charger and I thought MAYBE it was somehow picking up eletricity from that. So I made sure it wasn't close to anything electrical.
I got home at 5pm and it was still going. The light is only about half as bright as it was this morning. In another 15 minutes, it will have been on for 24 hours.
remember, theres NO battery in this thing, only a capacitor (unless they lied about the way its made.)
Whats going on here?   

[Queen Bee]

That is really interesting. I know very little about electricity besides what I was taught in Elementary school, but it is fascinating to hear about these kinds of things. I'm surprised it has lasted so long...

Too bad we didn't have these flashlights when I was in school. It would have made a fun science project/experiment for class.

[Dr_Demento]

I don't know if it will work this way or not.

But what I read said 20 minutes bright and UP TO 2 hours before it goes out. Assuming it dimmed right after I left this morning, it should last until saturday afternoon (I think thats Sunday on this board)
surely not 
they must have hid a battery in there somewhere. 

[SensoVision]

hehe, I always love such items and even see advertisment of this flashligh although they are not available here
Anyway I think that there are two possibilities, there is either strong magnetical field in your house which definitely isn't good(but I doubt this strong field exist). But maybe it's worth to check what level of EMI is in your house? The most simple idea how to check it is to go around home with compass and see how it would work. You may also put flashlight into metal box(it should stop magnetic field from charging flashlight).
But I seriously doubt that problem is in EMI, guess that because it's using led light which has very low power consumption(my girl had led light, she use it for pretty long time with the same battaries, during this time I had to charge mine with usual bulb few times).
Not sure how to explain things written by manufacturer, maybe with time it's performance fall to the level written on the box or they installed by mistake capacitor with higher capacity

[donecweb]

Here is what I know of these flash lights and the way they work. These flashlights were (as far as I have read) first introduced in the US around 1930 and they did work. But due to the poor efficiently of the bulbs then they were weak and didn't last long. So they were not popular. Then new advances in bulbs caused them to be more efficient then along came the LED's with their long life and low power requirements making these flashlights work quite well, but as yet have not become anything but a novelty. The way they work is the same manner as an electric generator. As you shake them or in some cases crank them the movement moves a magnet within a coil of wires. This generates electrical current to flow within the wire and this current is stored in a storage cell. The better one of these is made the longer it will hold the charge and work but there are some cheap ones that still use bulbs and are not very good. If you have one placed next to an active electrical field such as a transformer and it is in the right position it would be possible for it to keep the LED lit for an indefinite period.

[Andy]

The LEDs are super-bright white leds so produce light with very little current. The capacitors are probably the latest technology too with high capacitance and low leakage. The kind of capacitors that used to be used for data retention in computers. So you could expect a faint glow to remain after many hours after the initial charge.

There should be an initial bright light which dims exponentially as the capacitor discharges. If it stays bright for hours then Don's theory may be coming into play. Maybe the field from a UFO 

[Dr_Demento]

It finally burned out about 2pm today, thats 42 hours. Pretty good run  But then I shook it up and it lasted about 3 seconds. 

So lets see, assuming it will work at all. If i want it to last 42 hours again, I'll have to shake it for about 3 weeks. 

[SensoVision]

maybe manufacturer predict that people would put such heavy load on them during test and put these specifications forseeing that after these tests flashlight wouldn't perform longer than 2 hours

[SensoVision]

few days ago I've saw similar looking torch which cost 2$ only, so after Doc's story I thought to try it myself.
For some reason it was glowing when I take it but this didn't worry me sine I thought that someone before me charged it... after I come home I've look on the clock and turn it on to see how long would it lasts...
it worked 9 hours after which it died... I've tried to shake it but it doesn't make it doesn't glow...
After this I decide to disassemble it and check what was inside...
and here is what I've found:
two LiOn battaries instead of capacitor or reachargeable battaries, some piece of metal which should actually be a magnet(I've checked it but it doesn't attach to metal at all)... First I even tried to put real magnet insdie thinking that they just save on magnet and if I put it inside LiOn battaries could be charged a bit... but it doesn't help, so I've tried examine more carefully wires which goes from transformator(don't remember right name for this thing) to battaries, and find out  that both wires was simly shorted on same point so couldn't charge anything... 

Too bad I didn't have luck and wouldn't posses such shaking torch for such appealing price 

Anyway I posting this material along with picture hoping that other wouldn't get faked torch as me... check it befory buying to see if it's really charging from shaking or not

[Andy]

With the torch switched on and you shaking it, the light should glow brighter. That's a simple test you can do.

Sorry you got ripped off. At least you can use it as a club to beat them over the head next time you visit this market place 

[SensoVision]

Sorry you got ripped off. At least you can use it as a club to beat them over the head next time you visit this market place 

it's very light so wouldn't be hady to use as a club

Anyway I've found very small shaking torch here: http://gadget.brando.com.hk/prod_detail.php?prod_id=5&cat=Gadget+Torch&dept_id=1&dept=Gadgets&cat_id=27
it's seems to be very small only 6.5 cm long, so would easily fit into my hand and pocket. I've wrote to owner and they assured that this is real shaking torch so probably I'll give one more chance for this device.

[rosie]

LOL! You guys are funny! Sounds like a "disposable item" and you want it not to be! 

[Andy]

I'll give one more chance for this device.

Don't shake it too hard or it may fall to bits!

Alternatively, if it doesn't work, kick it around the room and stamp on it hard 

[SensoVision]

LOL! You guys are funny! Sounds like a "disposable item" and you want it not to be! 

yeah, we're wired

BTW I've wrote to shop owner and seems that flashlight isn't so small, there was mistake in numbers... so smaller flashlight is 17cm.
So now I'm asking about additional details about this model: http://gadget.brando.com.hk/prod_detail.php?prod_id=6&cat=Gadget+Torch&dept_id=1&dept=Gadgets&cat_id=27
Hopefully it's size(13cm) is correct one

[SensoVision]

Doc, so waht about your flashlight? is it still working if so for how long? And maybe you can tell it's brand?