Are there any GOOD shake lights?

[Hellbore]

You know the LED lights advertised on TV that you shake to charge up?

Are there any that actually work well?

See, my dad has received 2 of them (different brands I think) and so far both are crap. You have to sit there shaking them frantically for quite a while just to get a very dim and VERY purple beam, it's really quite sad.

Also, these are supposedly for emergencies because you can generate the power yourself, but... Don't they have a small battery of some kind? How do they store the charge? Or do they just use a capacitor?

I think it would be kind of cool to have one if it actually worked well and didn't have any parts that could degrade over time.

 

[SpeedEvil]

They have a capacitor - in general this is quite adequate, rather than a battery.
The fundamental problem - and why the capacitor is adequate - is that your arm +torch weighs maybe 3 Kg.
The movable magnet in the light weighs maybe 50g or so.

So, around 1% or so of the weight you're moving when you shake the light is actual magnet, and 99% is 'waste'.
If you can put 50W of power into shaking, then you can get _at best_ .5W out of it.

In an ideal condition, this would power a single LED at its nominal current for 5 times the time that you shake it.

Consider also that single AA sized lithium battery running a LED at its nominal current, with a 60s timer, can provide 1200 equivalents to several minutes of shaking, up to 20 years or so from when it's bought.

 

[Hellbore]

Wow... good info! Further confirms the notion I had that shake lights are stupid and worthless gimmicks

Just a thought though, why not make the magnet heavier and more powerful (Neodymium?) and use more windings on the coil?

 

[Rob187]

I've got a Nightstar 2 - I would not describe it as 'stupid' or 'a worthless gimmick'.

It is interesting for a number of reasons - the physics involved, the design and seeing through to the working parts.

No, it is not bright. Yes, the run time is poor compared to a battery powered light. No, it is not practical. Yes, it is quite large. Would it be of any use in an emergency - pretty much no. Would I throw it away - no.

 

[Planterz]

If you need an emergency light, you're better off with a regular light with a long running "low" mode and lithium batteries. If you must have a light that requires no batteries, get a cranker. The Freeplay brand ones seem to be the best.

 

[Xzn]

I was at target a few weeks ago playing around with a shaker flashlight. My girlfriend is aware of my passion for flashlights so she never stops me.

However this time, after a few seconds, she promptly stops me. I ask what is wrong?

She said I looked as if I was masturbating from the angle that she was standing. :laughing:

Never occured to me until she said that.

Then a few days ago we were there again and we saw an old guy trying a shake light. We both shivered and moved on.

 

[SpeedEvil]

Wow... good info! Further confirms the notion I had that shake lights are stupid and worthless gimmicks

Just a thought though, why not make the magnet heavier and more powerful (Neodymium?) and use more windings on the coil?

The good ones already use it - and as much windings as are possible.
More copper helps - but copper is heavy (not to mention expensive).
Yes, you can wind up the weight of the magnet, but you then need more copper to effectively remove the energy from the magnet.

On the silly side - sodium is actually a much more weight efficient per unit conductance metal to use than copper.
It does have problems though
And until you get the weight up into the hundreds of grams route, it's not really very much more efficient.

And once you've done that, remove the shaker, and stick a couple of batteries in, and it'll do the equivalent of thousands of shakes.

Wind-up lights are orders of magnitude more efficient, because it can be a low speed action, and pretty much all of your winding energy goes into the batteries/LED.

 

[DonShock]

There are some decent shake lights out there. Unfortunately, they are one of those tings where you get what you pay for. The one I like best is the full sized NightStar for $40. It actually works the way the cheaper ones are advertised. It requires a fairly short shake time to fully charge the capacitor and will put out a usable amount of light for several minutes. The only other one I've found that I consider acceptable is the Diamond Gen. IV for $25. Ignore the 1-2 hour claim, that's how long the LED will be lit, not how long it's usable. Although the usable runtime on a full charge is longer than the NightStar, it takes a more shaking to reach a full charge. So, if you ever need to use the light for an extended period, the NightStar ends up being more practical. When it starts to dim, a quick shake gets you another couple minutes. The Diamond's longer charge time is more of an interuption and is more tiring. However, if price is an issue, the Diamond still does work the way it's supposed to.

 

[PEU]

put two more magnets inside on the travel extremes with the oposite field of the moving magnet, that would help a lot the back and forth movement.


Pablo

 

[MrAl]

Hi there,

I have to favor getting a long run time light (low LED mode) instead.
As an alternate, the 'wind up' type LED lights are not too bad if you
get the right one. A friend has two of these lights and one keeps the
charge for a long time while the other looses it overnight, but they
both work ok after maybe ten turns of the crank on the light.
Dont expect super brightness, but at least they work.

The lights that have a 'low' mode use very little battery power and this
means they can run sometimes for a month without a recharge.
One of my Li-ion lights is like this. It puts out normal light at 350ma but
has a low 20ma mode too, as well as a medium setting.

You can also build your own with an LED, resistor, switch, and battery(s).
Connect all of these in series and mount inside a container of some sort.
There is nothing like building your own light where you can build any number
of dim settings you like into it.

 

[thunderlight]

What I would like to see is a crank based recharger that could charge a single AAA or AA battery. Even if you cannot achieve a full charge, it would be a more effective solution than the current crank lights or shake lights. In addition, you might wish to add solar like the solar panel on a solar pocket calculator. The unit should be small, portable, and if possible, water resistant or water proof. You would only need to use it in emergencies and "in the field".

Then your emergency light could be any single AAA or AA keychain light. Another possibility is a similar charger for coin cells. This would charge a coin cell that a Photon type light could handle. However, I have never seen a rechargeable coin cell in the consumer market and/or an associated charger.

[Some crank lights apparently use a rechargeable lithium-vanadium? coin cell.]

 

[DonShock]

put two more magnets inside on the travel extremes with the oposite field of the moving magnet, that would help a lot the back and forth movement.


Pablo

That's one of the differences between the NightStar and the Diamond. The NightStar has the magnets at the end and it is much easier to shake. The Diamond just has rubber bumpers.

 

[Theatre Booth Guy]

I've got a Nightstar 2 - I would not describe it as 'stupid' or 'a worthless gimmick'.

It is interesting for a number of reasons - the physics involved, the design and seeing through to the working parts.

No, it is not bright. Yes, the run time is poor compared to a battery powered light. No, it is not practical. Yes, it is quite large. Would it be of any use in an emergency - pretty much no. Would I throw it away - no.

My situation exactly - it's cool to play with from time to time but never my thought for a light to grab in ANY circumstance.

 

[Christexan]

Also, as you increase the coils and magnetic strength, the resistance to motion through the coil increases, meaning you have to shake more energetically to move the magnet through the coil. You'll generate more power per cycle, but you'll also be working harder to generate the output needed... at some point your human efficiency of moving the magnet through the coil is optimal, beyond that it gets so hard to accomplish that you are wasting more energy trying to move the magnet than the gain in charge.
Winding is much MUCH more efficient in comparison, with a shake light, you only generate power as the magnet moves through the coil, then YOU have to stop the entire mass of the light, reverse it's direction, repeat... so for everytime you move the magnet, you are having to start and stop the flashlight's momentum (generating no power during this part of the cycle). With winding methods, you are constantly moving the magnet through the coils in on direction, there is only one start phase, and one stop phase (and you generally don't use any energy in the stop phase, you just let go), for the entire duration of the winding process, and you are only starting and stopping the charging circuit components, not the entire mass of the unit.

<edit> wow, while posting that, there were like 5 more postings made, sheesh! Peu, are you saying basically to "bounce" the magnet off opposite polarity fields at the ends of travel? Not a bad idea, reduces some of the stop/start penalty at least, a recoil effect off the mass of the flashlight itself (would cut the wasted energy at each end in half if I'm doing my mental calisthenics right (equal and opposite reaction). Also increases the total mass though with 2 more heavy magnets... so that penalty has to be considered... I've got too much work to do to stop and consider further, LOL

 

[heliyardsale]

would an EMP kill a shake light????

 

[Christexan]

LMAO, interesting question about EMP, if referring to a tactical level one, my guess would be yes, the current induced in the coils would probably either overheat them and burn them out, or rip the light or coils physically apart (not to mention the magnet's potential to rip through the body of the light itself). Not my area of specialty so those are just idle thoughts which may not be accurate. I'd be more worried about my bank accounts though than my flashlight.

 

[MrAl]

Hi again,

Yes, with a shake light much energy is lost just because of stopping
and starting the movement of the mass. This inertia has to be overcome
with every single shake.
Perhaps a better arrangement would be to have the magnet mounted
on a circular path guide where it could be forced to move around the
path by rotating the light repeatedly, making a circular motion with the
hand/arm.

Hey, how about a 'water wheel' light where you hold it under running
water to recharge ?
Mounted correctly, every time you flush your toilet you recharge
your light

 

[Curious_character]

Has anyone measured how much power you get out of one of these shaker or crank generators?

c_c

 

[2xTrinity]

I've always thought that shaking was an inefficient mechanical mechanism. Why don't they assemble a similar flashlight using a magnetic piston and solenoid, similar to a hand-operated air pump? By utilizing this sort of pumping action, you could deliver a lot more useful power in a single stroke than minutes of shaking, squeezing, or cranking the lights available now. The piston could twist and lock shut as soon a you are finished charging it up.

 

[Hellbore]

I was at target a few weeks ago playing around with a shaker flashlight. My girlfriend is aware of my passion for flashlights so she never stops me.

However this time, after a few seconds, she promptly stops me. I ask what is wrong?

She said I looked as if I was masturbating from the angle that she was standing. :laughing:

HAHAH!

"That's hot"...