MDXL 3W Ebay cheapo clone project idea-HELP!

[Pokenaut]

I (like many others obviously) purchased a MDXL 3W Luxeon clone flashlight on Ebay. Here's a what I am thinking of doing, and I hope you experts will assist me in my thinking/actions:
Take the sucker apart, separating the head from the body containing the 3AAA battery holder.
Assemble two RS 4-AA battery holders in parallel, and load them with 2300 mAh NiMH batteries.
Cap the head unit and design a helmet mount for use in late night mountain bike rides.
Questions are:
-since the 3 AAA's that it runs on are 4.5V total, will running the 3W LED on 4.8V work ok?
-If not, what size resistor would be needed and how to wire it.
Since I would theoretically then have 4600mAh capacity, what is the expected runtime with this Luxeon clone LED?
Thanks in advance for your help, and GREAT forum!!
Dan

 

[Leeoniya]

looking at this datasheet, http://www.luxeon.com/pdfs/DS45.PDF

you'll notice the typical voltage is 3.7 with max of 4.47. 4.8 seems a bit over the top...that is if you're 100% sure it's a LuxIII.

at 700mA it's at 3.7.
at 1000ma it's 3.90.

from a 4.8V source, you need to drop 1.1V and 0.9V respectively. so using V=IR, 1.5ohm for 700ma and 0.9ohm for 1000ma. also note the resisots will need to be able to handle dissipating 0.77W and 0.9W. so they'll get warm.

i suggest using some regulation if it's not already there.

 

[davidefromitaly]

i suggest you to use two or three stacks in parallel of 3xAA ni-nh for not melt the led... i don't like the resistor because it waste a lot of energy

 

[Pokenaut]

So is there any other advice the illuminated sages can offer?

It varies between adding a .9 ohm resistor or just running 3-AA NimH direct?

I also heard I thought that a regulator could be stripped from a cheap Lux1W Dorcy, but when I looked into THAT, it seems the Dorcy is direct drive as well.
Assuming when I skank the head off this MXDL, I should also mount the clone Lux3W to a decent heatsink with some thermal paste. Let's also assume that I will be drilling a mount hole in the head behind the reflector to mount a RS microswitch. Will the extra wiring and the switch add enough resistance to make a difference?
I am new at tinkering with these LEDs (although last year I DID design 28 beautiful HO scale street light poles with 3mm LED bulbs for my slot car track) and obviously with the cost dropping on Lumileds and with clones appearing, it may be time to see what they can do off-road.

Dan

 

[Ctechlite]

I bought an MXDL 3w off of ebay, the emitter was a batwing. I believe that they do not make 3w batwings, so this light is only 1w. Be careful how you drive this, you may pop your led.