Using DX C30 with extension tube with 18650?

Can I use the DX C30 flashlight (uses 3xAAA) with a 18650 if I get an extension tube?

The voltage is ok, but I think it's direct driven - how will it react to the stronger battery? Is it only a matter of (much) longer runtime?

If purely direct drive that will be no good... i would advise against it.

Too much current?

But how does it handle current with the 3xAAA? Just pulls as much as it can?

I never saw it pull more than 450mA, is this the limit of AAA?

I've gotten almost 1.6amps out of a 3xAAA setup, so the batteries are not the limit.

About the C30, I don't know if an extension tube is readily availabe. May just be better off getting an x2000 - which is the same light, only a bit longer (and with ribs inside to keep the 18650 centered).

There's this:

If the batteries aren't the limit, then what is?

Maybe a resistor?

I'll just have to disassemble the light, I guess...

I have/had an X2000 from DX.


It is junk.

It now produces no light but pulls 8 amps from an 18650 and smells very, very bad.

No abuse, just a crap light. It killed itself without any provocation.

I am direct driving c30 from 14500 li ion... No problems so far. It puls 1,4A, gets hot, but not too hot. Runtime is a problem, so I will get this extension to use with 18650 (thx for the link!)

Hmm, I found this:

Looks like before the mod the LED was direct driven with no resistor, right?

And Don, thanks for the warning.

Looks like I can't get triple the runtime with a 3$ upgrade. :/

3x AAA alkaline (fresh out of the packge) = 4,8V, but the internal resistance of those batteries is higher than the resistance of a 18650 lithium-ion cell. So the current could be a little higher on a 4,2V 18650 cell, but i don't think that will destroy the led.

I have done some tests with this 3x AAA bike-light, modified with a XR-E R2 led: . With a 14500 cell it is just as bright as with 3x AAA Nimh cells. But the 14500 dous not fit without rolling some thick paper around it (it was just for testing).

If there was a lithium-ion cell with a diameter of 21-22mm and 52mm length, it would fit in the battery tube. A protected 21500 schould be perfect to replace the 3 AAA cells (with the protection circuit it will be a bit longer than 50mm).

I disassembled the pill - it is indeed purely direct driven.

Connected to an empty circuit board (only + and - connections) with no resistors.

Ah, well, was a nice idea.

I hope it works for you, UDO!

I think it works because thin wires to the led somehow limit current enough so that led doesnt blow

Maybe. :)

But just for fun - if I wanted to add a driver - would it then be safe to use 18650?

What driver would you suggest for this light?

It was my first mod. I've used driver from DX Sku.7612 but you can use also Sku.6190. No problem to use 18650 with those.

But if you make sum of ext. ring and driver costs, you are allready over half of the price for a new 18650 zooming one.

Yeah, but just for fun :)

And thanks for the suggestions.

Isn't 1000mA the upper limit of XR-E? Shouldn't I choose a driver with less output than that at high?

At least in theory. Many people have driven XR-E's at up to 1400mA though it will not last as long at that current. Heatsinking is imperative for you to be able to drive them hard.

Well, there's hardly any heat sinking in the C30.

It's just a hollow aluminium pill with very thin edges, and the empty circuit board and led star constitute its bases (air between them).

I don't think I should drive the LED at any more than 700mA (which should be plenty bright for my needs - with the current 300-400 mA it draws now it is bright enough).

I just wanted to use the 18650 to gain more run time, not more brightness (but that's a bonus, obviously).

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