Using DX C30 with extension tube with 18650?

The internal resistance of an 18650 is very, very much lower than that from 3 AAA cells in series, so current will be a lot higher.

So if you don't add a driver you will have to add some resistance. I'd start thinking around 2 ohms - start with 5 and measure the current.

Or add a driver.

If you are happy with the current brightness, I'd go for a 350-500mA driver - you get the same output and 5-7 hours runtime.

I was thinking about a resistor, but I think I want to be able to also use the flashlight with the 3xAAA option.

I guess a resistor will make the current much lower in this case?

Is there a suitable driver for this?

[I should really have openned this thread in the modding subforum...]

It ought to be possible to bodge a resistor in somewhere that it can be removed when required. Or turn it into a twisty and use some quantum tunnelling material between a couple of bits of metal as a switch. The stuff is cheap.

I doubt even good AAAs can sustain 2A for any length of time, even the worst 18650 shouldn't even break sweat. If the light is designed to limit current depending on the internal resistance of the cells, lowering the resistance of the cells will inevitably raise current. All cells sag under load - alkaline AAAs sag hard - 18650s sag a lot less - so you have at least as many volts and more amps.

I'll try this with a Solarforce L2i which can use both.

With a Solarforce 0.9-4.2V single mode dropin.

Three LSD AAAs, 4.264V output on lightbox and current

1080 lux & 940mA

18650, 4.189V output on lightbox and current

1402 lux & 1620mA

That's what is coming out of the cells. Emitter draw is harder to measure and requires soldering before and afterwards. 1600mA is almost certainly losing a fair bit as heat. 4.2V is well past the Vf of the LED so I suspect the driver is dumping quite a bit of that as heat. You'd need to ask one of the guys round here who knows about electronics about that - my knowledge could be printed out and comfortably inserted into my eye.

The OP light says the emitter is a Cree P4 so around 1000mA Cree spec but you should get away with 1200mA in short bursts without cooking the LED. 1400 if you have really good heat sinking.

So if I take the resistor approach - I guess we're talking about at least 2W resistor? Preferably 3W I guess.

If I know the internal resistance of the battery / battery pack - can I calculate the current I'll get through the resistor? If so, I may be able to pick a resistor such that it will work well with both battery configurations.

Couldn't find a suitable driver, though I searched qutie a bit. Seems that drivers whose max output is below 1A are taking only 1.5V input, but maybe I missed something.

I just got the extension ring I linked to above.

It doesn't fit the C30 - the threads diameters don't match :(

Ah, well, another 1.56$ lost in the pursuit of the perfect torch :)

Well, yesterday I bought this extension ring too :( How much is the difference in diameter? It doesnt fit even if you use force?

It's too small, not too big.

Maybe you could use some conductive metal sheet as spacer, but it won't be nice and I doubt that replacing the batteries would be fun.

I guess you could solder it to the C30 tube, but then you'll only have 18650 and not 3xAAA.

Got some great news for you Haggai I received the extension ring and like yours it doesnt fit... BUT I was so frustrated to fit an 18650 into c30 that I figured it out! 18650 fits C30 without extension ring! You just have to remove the tailcap spring and unscrew the ring that holds the switch. Now you have almost 1 cm more space and 18650 fits without a problem! Just try it! And to make things even better (at least for me ) the extension ring fits onto another 3xAAA light that I got.

I really love my C30 now - its really small for a 18650 light - a whole 1 cm smaller than already quite small Trustfire TR-801 + its a zoomable light. Now if I could only somehow fit a QTC pill in it and it would be a perfect light for me. The led did turn a little blue (from 6 months on 14500 DD), but with QTC and improved heat transfer (thermal grease) I dont think it would be a problem anymore. Size comparison:


I was wondering where you guys got the extention ring and after hearing it doesn't fit ....ah .. never mind ...:~

I like my c30 if that is even what it really is ?? ..I have no idea what emitter is even in it but it's pretty warm and it's a 3 mode ..I still think it's a great light partially because of the tint ..maybe also because it was my first real led light

UDO, that's great news indeed! :)

I'll certainly try it today when I get home.

I think I am going to buy some more of this c30 like flashlights now - they are very cheap here - 4,9$: http://www.buyincoins.com/details/zoom-focus-3-mode-aaa-cree-led-flashlight-camping-light-product-2780.html + they are 3-mode + you can get -15% from that price with code (10%eBay110 and Recommender = nissius). I know that probably I wont get a cree emiter, but just because of the price and possible 18650 mod this seems a really good deal. Did anyone already bought this flashlight from Buyincoins? Is it any good?

Dirt cheap, but they have this annoying red ring at the head.

For 1$ more you can get one without the ring: http://cgi.ebay.com/Adjustable-Zoom-Focus-LED-Flashlight-camping-torch-LC3-/220741014541?pt=US_Flashlights&hash=item336530940d#ht_4483wt_1142 .

It's not Cree Q5 but Osram Golden dragon instead. At least a batch from a month ago was that. I've made complain and they say I either return item or partial refund about 1/3 of a price.

I can send you one if you want. More on PM.....

Oh, and there's a probably CREE one (judging by the pictures) that comes with a fitting extension ring, so no need to mod anything, at 8.59$: http://www.ultraok.com/zoomable-3-mode-cree-led-aluminum-flashlight-torch-200-lumen-1xextension-ring_p1826.html?cPath=882_884

"Not Available to Slovenia"

Or to almost anywhere else in Europe... very weird.

But you could always ask the seller if he is willing to send to your country, they usually say yes.

This one http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&rt=nc&nma=true&item=140518130710&si=urorNXPV9iEvF728XiK%252FC7EZO4E%253D&viewitem=&sspagename=STRK%3AMEWAX%3AIT includes holster.

So, it does work :)

0.4A with 3xAAA, 0.5A with the crappy Ultrafire LC 2400, 0.95A with the flame Trustfire 2400. That's direct driving a Cree XR-E P4... not bad. :)

But I still prefer to not need to hold everything in place whenever I want to change battery.