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Shake generator in battery compartment

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kangyunmei

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Hello friends,

I have some led flashlights that take 3 AAA batteries. I wanted to replace this with a 4.5V rechargeable battery/capacitor And a shake generator (Faraday) in the battery compartment.

5 Pack Ultra Bright LED Flashlight Torch 7w 300lm Adjustable Focus Zoomable Q5 Cree Tactical Light

The flashlight I only would need for 2 minutes at a time.

Would it be possible?
 

Hi,

Pleae mind: a forum can't replace scool.
Thus I recommend to first study electric / electronic basics.

*********
To your question:
There us a lot of useless information:
* Ultra Bright LED Flashlight Torch ...300lm Adjustable Focus Zoomable Q5 Cree Tactical Light

You need to learn to focus on the problem.
The problem is just "energy".
* calculate how much energy you need to drive your application for the given time
* then calculate how long you have to shake your generator for this electrical energy (here we totally miss electrical specification of your shaker generator)
* for more precise analysis you should take "efficiency" into account.

Then decide on your own if you find it useful.

Klaus
 

I assume "5 Pack Ultra Bright LED Flashlight Torch 7w 300lm Adjustable Focus Zoomable Q5 Cree Tactical Light" is a reference to an advert somewhere.

I very much doubt you would be able to do it with a 'shake' generator. At 4.5V and 7W output it would consume at least 2 Amps (W = V*I) allowing for inefficiencies so even with new good standard batteries it would only last a few minutes. Given the time it takes to re-charge a battery to get appreciable life out of it, you would have to 'shake' for several hours to get a few minutes of light. Even Elvis Presley couldn't manage that! A capacitor with large enough value to sustain 2A discharge over several minutes would be impracticably large.

Brian.
 

I have two 'emergency' white led flashlights which are human-powered. They make a sound of a small generator which is probably a dc motor.

a) The squeeze light must be worked rapidly. It's always jittery since my hand is moving around. It goes dim as soon as you stop.

b) The windup light has a crank (similar to jack-in-the-box). After several seconds of rapid turning, you can stop and it stays lit for about a minute, gradually going dim. Tutorials suggest power comes from a capacitor rather than a battery.
 

Crank types are much better than 'shake' types but as Brad points out, the light only lasts briefly. With a high powered LED (room lighting power) it would last significantly less time. "Shake" generators have a coil around the center of a plastic tube which holds a cylindrical magnet. There is a spring at each end of the tube to 'bounce' the magnet back and forth but the motion required to keep it passing through the coil is a fairly violent shake of 30cm (12") or more. One I have here holds charge in a 0.47F capacitor but it takes 5 minutes of considerable effort to light a 5mm white LED for about 30 seconds. The amount of movement needed to keep it lit make it useless as a flashlight!

Brian.
 

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