Plastic Dorcy Keychain Light- Battery Module

[RebelXTNC]

Sears sells a plastic Dorcy keychain light for $4 that uses a battery module with 4xAG3 batteries and a 5 ohm resistor.
This battery module is slightly longer than a regular AAA battery but a regular AAA fits fine since the tail spring is long. I don't have a 10440 lithium-ion AAA-sized battery to test in it.
I wonder if a slightly used 3.7v would make the 5mm LED go POOF!?
If it worked this would be a killer bargain for a waterproof lightweight backup light. The head reminds me a lot of Underwater Kinetics small lights with a twist to tighten for ON head and an O-ring.
Here's the light:

http://www.dorcy.com/products.aspx?p=411415

Anybody want to test out this theory?? The polarity is + towards the tail spring.

 

[Lynx_Arc]

I took one of those and replaced the spring contact assembly with a shortened assembly out of a pelican 2AAA incan used the spring out of the pelican too, cut a piece of clear waterline hose and put in a 1-5 cell maglight LED module and I have a bright floody light that runs well of 1AAA cell

 

[Lynx_Arc]

oh and the lens/led module fits the UK2AAA too just use 2 AAA lithiums batteries and you have an LED version instead of the incan model.

 

[RebelXTNC]

That's very cool about the UK lights, since I just happened to have two of the 2AAA incans sitting in a drawer not being used! I had always thought the price of the UK LED module was too high, but now I can use both of these bodies again for only $8 total!
This LED will run on 2AAA alkalines too but I'm sure 1.6v lithium primaries would last much longer and be brighter as you suggest.
You have to reverse the placement of the cells (which I forgot to do after having to exchange bezels and re-lube the dry O-ring.) The alkalines didn't fry it though so either they were too low a voltage or there is some reverse protection in this Dorcy module.
I couldn't get the Dorcy threads to grab since they are slightly different than the UK, but the modules are easy to switch out and use the original bezel.
I guess I'll go back to Sears and buy two more. One for the other UK and the third to experiment with a lithium-ion rechargeable.
Do you have any pictures of your creation using this Dorcy light?

 

[LEDninja]

The AG3 are alkaline and have very high internal resistance under load. This limits the current to a very small value.

A lithium ion have very low internal resistance resulting in very high current (1200mA measured when used in a Fenix L0D CE). This will certainly fry a 5mm which is usually rated at only 20mA.

 

[RebelXTNC]

The original Dorcy battery module with 4xAG3 batteries and a 5 ohm resistor reads 5.5v with no load.
There is enough length available to put a disc-shaped resistor in the body tube with a 3.6v 10440.
I'll probably experiment with that just for fun once the lithium ion cells arrive that I was already going to get for my Tiablo MA1.
The Dorcy LED module seems to run fine on 2xAAA alkalines in the UK body. Just a little less bright than on the original battery pack.

 

[VidPro]

just notes, you realise that 4xAG3 or even 5 or 6 will only put out some 80ma MAX and that drops down to about 40ma very quick.
i dont know why they would even bother with the resistance, but being responcable they did keep it out of overdrive .

with a li-ion fully charged (4.2v) ~33ohm resister would do about 30ma (lite overdrive)
and it would still be plugging away at about 15ma when the capacity of the cell was mostly extinguished.
(note i am bad a math, so these are guesses, that would need to be tested with meter)

its a good thing to put such a cell (the 10440) in this design, because you can tune for the cell, and being SINGLE and WHITE led, the liklyhood of damaging the cell from overdischarge is much less (they arent protected) . charge it when it gets dim.

 

[RebelXTNC]

I finally got back to this project and went about it a little differently than I first thought. My mod is similar to what was suggested by Lynx_Arc except I didn't have to cut anything.

Parts List:
Plastic Dorcy Keychain Light minus the LED module (transplanted into a UK 2xAAA light) and original AG3 battery module (not needed).
NiteIze PR-based 2-6 Cell Drop-in (Target store clearance sale).
Lithium-ion 10440 cell.
Center spool from Butler dental floss (supports the round LED lens).

In my case that's it! Depending on the center spool you happen to get and the side contact of the Dorcy, you may need some insulating tape on the PR base and a contact ring to hit the PR flange. With mine it works fine so far without either of those.
Gives all flood and is fairly bright for a small, lightweight waterproof mini-torch. It also tailstands just barely. It makes a better hanging lantern since there is some spill from the translucent bezel as well as the all flood beam. The lanyard hole is about dress shoestring diameter once you remove the cheap keychain attachment.
You can also stand it on the bezel, more stable than the tail and still gives plenty of light. In addition you can place it bezel down on a white or translucent bottle cap. The bottle cap can be on the table or still on the bottled water!
Runtime is unknown. I doubt it will be very long but I'll have to test.

 

[Jumi]

Is this the same light as Dorcy:
http://www.dealextreme.com/details.dx/sku.5697

I looked at this few weeks ago, but didn't order since my order was 30$ already, maby next time?

Juha

 

[Lynx_Arc]

sorry no pictures. I still have both in my pocket but find I use the dorcy modded light the most often and have the UK as a backup

 

[Lynx_Arc]

Is this the same light as Dorcy:
http://www.dealextreme.com/details.dx/sku.5697

I looked at this few weeks ago, but didn't order since my order was 30$ already, maby next time?

Juha

looks identical to me, I bet they make the dorcy version in the same factory and just package/label it. Too bad there seems to only be one color though.

 

[Fallingwater]

Remove the existing resistor and replace it with an appropriate one for driving the light with a 10440. Then you can use the LiIon cell without fear of popping anything.

 

[RebelXTNC]

The Deal Extreme light is very similar but not completely identical to the Dorcy if you look very closely (vent nub on tail?, length of battery spring and battery module?). Although I'm not sure those pictures match up with it coming stock with a AAA battery. There is room for one inside, but the light in the Deal Extreme pictures appears to have an even shorter battery module than the Dorcy and a much longer tail spring.
My local Sears has a wide variety of colors; red, blue, green, and purple for $4 each.
The stock Dorcy battery module has the 4 AG3 cells stacked with an inline resistor taking up the rest of the space. The module is slightly longer than a AAA battery and it has a screw cap. With a 10440 and the stock LED module you would have to make a disc resistor instead of an inline.
Since the Target clearance sale made the NiteIze PR based LED's available more cheaply than normal, I went with one of those instead of having to make a resistor to fit inside the tiny space left after putting in a 10440.
To make my light 100% reliable in switching, I am going to add an insulator to the PR base and a contact ring for the PR flange.
I'll have to take some pictures after that.
I'm pleased with this setup of new parts, but if I hadn't already had a lot of it on hand and the NiteIze hadn't been cheaper on sale, it would be fairly expensive to put one together. But I have 4 complete lights that now work much better than they did originally so that helps spread out the cost.