Cree XRE Q5 Led Direct to Battery??

[dk11]

I have a left over XRE from a previous DIY light,and I am going to be using it for a trail running head light,
I have 3x AAA rechargeable NiMh battery to power it.
Would it be ok to connect the LED direct to the batterys (I will be using a simple on off switch in series) or will I need a resister/driver?

[brad72]

Since 3 x AA's give 4.5 v a 3.9ohm resistor to give an output of 350mA or just use 2 x AA and no resistor. To get an output of 500mA use a 2.7ohm resistor with the 2 xAA's.

[Vancbiker]

I have a flashlight that uses 3 alkaline AAAs and drives a Luxeon 3 directly. It works even though the voltage is higher than the Vf of the LED because the AAAs can't deliver more current than the LED can tolerate. I have never tried it with NIMHs so your result may differ.

[dk11]

Since 3 x AA's give 4.5 v

I was thinking of using the 3 x AAA to keep the weight and size down since NiMH cells have a run voltage of 1.2V(as far as I know),and I'm sure the XRE was rated at 3.7V

[dk11]

I have a flashlight that uses 3 alkaline AAAs and drives a Luxeon 3 directly. It works even though the voltage is higher than the Vf of the LED because the AAAs can't deliver more current than the LED can tolerate. I have never tried it with NIMHs so your result may differ.

The batterys I'm using are 850mAh,and again not sure,but I think the XRE was rated at 1 Amp

[Goldigger]

I've done it from a single 18650...yes it smoked the XR-E

[HEY HEY ITS HENDO]

AAA`s are not very powerful, you will be ok direct driving,
of course the XR-E will need to be on a heatsink of some sort!

[dk11]

Well,here's the finished product...









....Ugly as hell but gets the job done
I had a look around,and found a DX driver I had ordered a while back and never used.
Took it out for a 40min run last night,it gives off plent of light for running.

And while I'm at it,these are my bike lights I built a few years ago(soon to be converted for bar mounting)

[Toaster79]

I've done it from a single 18650...yes it smoked the XR-E

No wonder! I'm squeezing 3.5A out of 3000mAh freshly charged ultrafires