Building alittle copper pocket rocket

I'm building a little copper pocket rocket and I still have a few things to decide on.

The led:
A cree XPG2 or XML2 on a copper mcpcb.

The battery:
A small cyclindrical rc battery similiar in size to a AA, but rated for 25c draw or an IMR16340.

I plan on heavily over driving the leds, 3amps and 5amps respectivly.

I'm thinking direct drive for high and then a single amc7135 for low.

I'm leaning more towards the IMR16340 because I feel it would be smaller and more impressive when turned on

I'm going to use the same optic nomatter the led, a carclo 20mm narrow spot.

Do you think its worth using an xpg2 for the tighter beam? An XPG2 gives an 11 degree beam while an XML2 gives a 17 degree beam.

There are goods and bads about running the XP-G2 at 5a. For a small guy, it'll be a lot of trouble trying to manage the heat.

I'm already having issues with the heat on a local's Solarforce. It's pushing 2.9a at the tailcap on the XP-G2. The whole reflector is machined to fit into the aluminum cup. The cup is machined precisely to fit tightly into the head. The light is then plunged into the pool on high and still hot after we pulled it out.

The XM-L2 will not be as hot but will not have as far of a throw compared to the XP-G2.

Nice project parameters. Few things to look into: the 7135 driver is basicly a limited direct drive on full. You will need enough voltage to be able to supply the LED with enough current.

So a 1.2v battery will not work for any of them, unless you will get a boost driver (and not many will be around which take 10A 1.2v in and 3.3v 4A out. Most boost drivers taking 1.2v volt are very limited.

Secondly, I know for a fact that getting that high drivecurrents even from a IMR 18650 is difficult if you must retain the high Vf of an XML2. Mine did 3.6v at 4.5A.

You will loose some voltage in wires, contacts and 7135 itself. Optimisticly, you will at least need 3.8V at the cell at the set drivecurrent. Even for a IMR 18650 this is difficult, let alone a 16340.

My advise:
- use low Vf LEDs, this can be an "old" XML u2 or a XML 2 with just a low Vf( you will have to look for it!)
- look into 18350IMR cells, but I can understand that this is a little too thick.

Good luck .

Ever thought about using the Xp-e2? Can't be driven as hard but it's surprisingly bright for its size and will allow you to use the 16340 and have decent runtime.

I've got a vinhnguyen54 modified Maratac Cu 123 running a AW IMR 16340 with an XP-G2. Single mode 700 lumens and gets plenty toasty.

Ohh wow. that is awesome. so this is definitly doable.

I have looked at an xp-e2 but my goal isn't just throw. I want a general purpose light that can also make people go WOW. I'm going to go with an XML2-U2 and if it doesn't give enough throw, switch it out.


@Epsilon its a lithium polymer battery of all things. i guess it has just been rolled into a cylinder. Its rated at 650mAh and for 25C discharge. I can't remember the dimensions, but its smaller than an AA, what is that 14530?


By direct drive I meant just a mosfet so I wouldn't have to worry about a ton of amc7135.

I think the internal resistance of the battery plus the voltage sag under 5a load will keep the led from going *POOF*

Read that wrong indeed. I know they exist ( round lipos), but are usually very low capacity, 650mAh is much higher than what I've seen. Most of the time they are about half that for such small size. In return you get huge current potential, which might be able to drive the xml2 to its full potential.

It will get hot BTW, at 5A even a maglite 2d gets hot .

If you use a decent direct to copper bonded XML2, you probably don't have to worry about the led blowing up. It gains in light intencity up to 6,5A but will hold much more probably.

I found the battery. I'm pretty amazed by these batteries in general. I ordered a few a few weeks ago. Once they come in the mail I'll test them out.

http://hobbyking.com/hobbyking/store/__23317__Turnigy_nano_tech_650mAh_15c_Round_Lipo.html