Will my Cree survive direct drive?

[Lighthouse one]

I installed a Cree P-4 in a light with direct drive. I put in a McR-27XR reflector from the Sandwich Shoppe. I love it! Not a tight spot..but plenty of power and a strong wide spot the blends just right into the spill. I'm running a 3.7 volt battery...

Will I damage anything like this? What does a resistor do for this circuit if I need one..and what value?

Thanks for any suggestions...I'm trying to learn how to do these mods starting off easy.

 

[Nitroz]

I installed a Cree P-4 in a light with direct drive. I put in a McR-27XR reflector from the Sandwich Shoppe. I love it! Not a tight spot..but plenty of power and a strong wide spot the blends just right into the spill. I'm running a 3.7 volt battery...

Will I damage anything like this? What does a resistor do for this circuit if I need one..and what value?

Thanks for any suggestions...I'm trying to learn how to do these mods starting off easy.

You should really add a 1 ohm, 2 watts resistor to keep from frying the LED. I sure that right now the light creates some heat after a few minutes.

Do you have a DMM to check the current to the LED? I would say that it could be pulling 2amps from a rechargeable li-ion.

 

[nein166]

Do you have a DMM to check the current to the LED? I would say that it could be pulling 2amps from a rechargeable li-ion.

Call me a noob but would DMM be a Digital Multi-Meter?

 

[Lighthouse one]

THe cree is pulling 850 ma. It gets warm, but not hot after 20 minutes. I've run it several cyles and no problem so far..the light is well heat sinked. It not a Li-ion battery. It's a special made nimh . Where do you get resistors of that value? Not Radio Shack...I've looked on the net, but can't find anywhere that offers resistors around that value to the general public...I don't need 1000. When the light is on a while it just slowly gets weaker...and stays cool as it gets weaker.

 

[Norm]

How about: http://cgi.ebay.com.au/1-Ohm-2-W-5-...99526276QQihZ017QQcategoryZ4664QQcmdZViewItem
Norm

 

[Mirage_Man]

I've been running one in a Q3 for weeks now at just over 1A and it's still fine. :rock: Granted I am using a nice custom heat sink.

It may not last 10,000 hours but who cares?

 

[Nitroz]

THe cree is pulling 850 ma. It gets warm, but not hot after 20 minutes. I've run it several cyles and no problem so far..the light is well heat sinked. It not a Li-ion battery. It's a special made nimh . Where do you get resistors of that value? Not Radio Shack...I've looked on the net, but can't find anywhere that offers resistors around that value to the general public...I don't need 1000. When the light is on a while it just slowly gets weaker...and stays cool as it gets weaker.

If it's only running at 850, you should be fine.

Mirage_man,
The Cree at 1amp is awesome! I have a few that I run at 1 amp and they're excellent.

 

[Ganp]

I have a Cree XR-E which has been run direct drive with no resistor since last summer. It is usually in my EDC run from 1 x cr123.
I have just rechecked the current with a fresh cell - 1450 mA.
Other cells have run from 850 mA up.

When I get the chance I will also take some temperature measurements.

Of course this may not be doing the LED much good - I'll just wait and see how long it lasts.

Colin.

 

[Lighthouse one]

Thanks for the replies guys...I feel a bit better now!