Picture of Cool, Efficient, mag-lite
Replace the bulb in a 2xAA mag-lite with a bright white led. A cool burning led will give you longer battery life and won't burn your face off.

Step 1: Collect the parts

Picture of Collect the parts
You'll need a 3.2 volt LED -- I think most bright white LEDs qualify. A ruler or caliper. An old, beat-up mag-lite, the kind that takes 2 AA batteries. Some wire cutters. A low speed or variable speed drill and 1/4" bit (not pictured). A small vice or pair of adjustable, locking (vice-grip style) pliers will come in handy (not pictured).
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botronics3 years ago
The only rechargeable 1.5 batteries are the rechargeable alkaline type. Nicad and NiMH are 1.2 volts (1.37v hot off the charger) and never 1.5 volts. If you have a rechargeable Nicad or NiMH marked "1.5v" show me a photo. I don't like the rechargeable alkaline because they leak.
that comment was retarded made at 4 years ago and we all knows im wrong about rechargable 1.5vs

come on shut your yap and move on!
botronics9 years ago
No current limiting resistor? How long has it been burning? Does it work with rechargables?
It says 2AA battery equal as 3V, and this LED is 3.2V, so nothing is bad. And yes, rechargable works too, because they works as 1.5V each.
1.2v each, usually.
every AA battery i have ever used was 1.5 V...
Rechargeable batteries are only generally 1.2V unless they say otherwise.
i don't know i'm looking at my collection of batteries... (and i have a TON of AA's) and they all say that they are 1.5.... including the rechargeable ones.... what brand are you talking about???
All my rechargable AA's say 1.2 V
Just my 2 cents.. Where did you get rechargables that are 1.5?
Rayovac, Radioshack, Sanyo, and a couple more generic Chinese brands that I have. If yours are newer and 1.5V, that's great, more compatability. But as of a few years ago when I bought my last ones, the standard seems to be 1.2V for rechargeable AA's.
hmmm well then this is all news to me... this will be very helpful to me and my projects.... Thanks for the info 
Sorry, You are right. Thanks for the correction.
actually, 2 AA batteries brand new are about 1.6 to 1.7 v.
Prometheus9 years ago
light output might actually be greater than the maglite bulb, depends on the led's mcd. If you find a "superbrite: white, the LED will make a laughingstock of the old bulb. Alternative to drilling out the focus (reflector), you can find the same ratings for ini's and sub-mini's that will fit without any modification except to the LED lead length. You will know a superbrite if it's hard to tolerate it shining directly into your eye, and perhaps leaves a bit of retinal burn.
That's not the best way to test LEDs!!
Pwag phenoptix3 years ago
These guys are right, use someone else's eyes.
phenoptix Pwag3 years ago
6 years for a reply to that comment Pwag! But it was worth it!!!
Pwag phenoptix3 years ago
Ha! The internet is full of surprises some times!
Pointing superbrite LEDs at your eyes can cause retina damage it's a very bad way to do it :)
Guardians385 years ago
I have GOT to make this... im going to buy a flash light just for this =)
marselsipod6 years ago
DAMN! i just got my free LEDs shipped and needed a way to test them, and thought of it in the bathroom, was all excited, but then i found this instructible. damnit! but kudos to you for thinking of it 3 years before me =P
frusciante9 years ago
I think that without a resistor the battery life will be very small. The resistor is not placed in order to protect the LED from "blowing-up" as keng said. It is used to limit the current to save battery life.
keng frusciante9 years ago
Ahhhh....well, i stepped in that then. sorry.
tslibertan keng7 years ago
No, I think Keng is on safe ground. All you need do is get the voltage right (i.e to agree with datasheet limits). If voltage (per LED) is too high, you need a resistor, otherwise you may not.
That's not true. Depending on how much power you're using your LED may need a resistor to limit current to it. I've burned out a few LEDs by playing with how much power they can take (it actually looked kinda cool). If you're pushing more voltage than the LED can take it will fizz and eventually shatter, smoke, catch fire, etc. Your best bet is to do a little research online -- there are calculators for figuring how much resistance is needed for your situation -- and just saving yourself a headache. Also, you'll end up saving battery power in the end anyway.
Yeah, you always need a resistor with an LED, even if the LED is made to drop the whole voltage. Once an LED is passing current, its resistance quickly tends toward zero. I = V/R, so current draw increases to the maximum that the source can provide. It will be terribly inefficient, and might burn out the LED to boot.
see above.
tslibertan keng7 years ago
You don't always need to use a resistor. If the voltage is constrained to within specified safe limits (see led's datasheet) the V-I relationship for the specific led will show that it runs safely without requiring a resistor for current-limiting purposes. LED's are not devices that obey ohm's law. I have made a 100 UV led array without a single resistor. Not a single mili-watt is wasted on a resistor, has run beautifully for many hours.
bravebaker (author)  jaredforshey8 years ago
"Yeah, you always need a resistor with an LED"

I would have to say this statement is incorrect insofar as having to add more resistance in the form of a resistor. I got out the old multimeter last night and watched the current draw of the flashlight. It was around 30ma and stayed there for as long as I cared to watch it.

I'm willing to bet that Tazzz's comment about the internal guts of the flashlight providing a little resistance and the fact that I'm driving a 3.2v LED with <3.0 volts is what is keeping my LED intact.
Ashhow8 years ago
Can any one tell me if i could do this with my AAA mini maglite? i imagine it shouldas it still takes 2x1.5v cells
As long as it's a 2-battery flashlight, you should be able to use a bright white led. triple-a's you could just replace the bulb with the led, pop in fresh batteries, and have a nice bright light. As the voltage drops on your 2-cell flashlight though, the led will dim considerably. even with a double-A light, an incadescent bulb will still be dim but useful long after the LED is "dimmer than a politician". If you have a 3-4 battery flashlight, and use the proper resistor, you'll be good. Before anyone umps on me about that last statement... yes, on a fresh set of battries, a led conversion will outlast a normal bulb by many, many hours. The other cavet is, if you use rechargavble batteries, you'll only get 2.4 volt instead of 3volt. most bright white led's will barely be visible at that voltage, even though the amperage is plenty large enough. :-( Normal bulbs will only be slightly dimmer.
now is this brighter? or is the only plus that it sucks less juice and lasts longer?
bravebaker (author)  prometheus55007 years ago
Depends on the LED. The one that I used is probably about a 1/3 as bright as the regular bulb, but here it is 18 months later and I still haven't changed the batteries. My kid uses it all the time and forgets to turn it off, so I know it was worth the (tiny) effort. :-)
macmaniac8 years ago
rapid electronics in the UK sell a white 5mm LED at 25,000mcd for just 56p!!
I bought mine at Ledtronics out California. http://www.ledtronics.com/
i love rapid!! my favourite place for components. much cheaper that maplin (uk equivalent of radioshack, think they can charge whatever they what just because they have no competators with highstreet (as opposed to online) shops (stores).)
Klowd_138 years ago
im not sure if you herd of it....but they make a LED conversion for the mini mag
vtsnaab8 years ago
A few words of warning about that vendor:

I ordered from them - only about $13 worth of stuff, but I don't recommend using them.
They happily took my money, and almost a month and many emails later I finally got a
single reply from them admitting they had a system error and the order was never
processed or shipped, many weeks later it finally came, and was 1/2 wrong.
They don't answer emails and I am stuck with the wrong LEDs.

Since only 1/2 of my order is good, I actually paid 2x the cost of the ones they
got right...
There must be a better, domestic source that is better and as affordable.
ranjeevm8 years ago
I have ordered 13000mCd white LEDs from eBay at about $21. Once they come in I plan to hook them up with a charger, NiMH battery set to wire up a few emergency lamps. Before I do that, I need to know how much of biasing current gets the best intensity of light without any damage to the LED. If I use 4 X 1.2V batteries, is a 10 ohm, 1W biasing resistor enough per LED? How much of light is 13000mCd, theoriticallt it should be like lighting 13 candles in a room! So is just 1 LED enough for a medium sised room? If it is, how many are really required for proper diffused lighting? If anyone here has any idea, this would save me a lot of browsing for data sheets and trial and errors...this would be really really appreciated. Guys, please look up my profile. If your knowledge helps me today, mine will help you tomorrow! Thanks!!
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