overdriving LED's- question

Why is the lod-ce brighter on 10440's??

Just a simple question- i cant understand why it appears to be insanely bright when i thought there was regulation- doesnt this control the current to the actual lamp??

I know overdriving incan's is possible (and waaay improved my 3D mag when using 4C's) but i thought LED's regulated the current so putting higher voltage battery made no difference.

Is there also a list of other LED lights that you can overdrive?

Sorry if this is is obvious,
Robert

while i cannot comment directly to the LOD-CE, many regulation circuits go into direct drive when voltage in is greater than the forward voltage of the led.

You are wrong on both light sources and very lucky with the overdriven incan
(lies in internal resistances of batts). If You happen to get extremely good cells, You re prone to instaflash (way too much current because the cold wire has nearly no resistance --> melts)

With leds its a bit different: slightly increasing voltage means greatly increasing current, the led does not regulate current at all (its the circuit of the led light that does, but might be fried also)

in short: with either light source You reduce the runtime very much.
If the led is sinked very good, it wont die too quick.

Robatman said:

Why is the lod-ce brighter on 10440's??

Click to expand...

Many regulators in lights will overdrive the LED if given a voltage that is out of spec. Because the 10440 is of a higher voltage than the voltage that the regulator is designed for, it no longer behaves as you would expect, hence the brighter output.

another way to look at it is: with AAA alkaline or nimh, it just cant draw as much current as it can on li-ion due to internal resistance.

It also depends on he flashlight model...

The single cell Fenix models like L0D, P1D, P2D (and 2x AA cell) use a "boost regulator" which can take voltages below ~3.7 Vf of the LED and raise it to the 3.7Vf required by the LED. This type of regulator cannot regulate over 3.7Vf (volts forward biased LED) and simply pass the voltage/current through (limited by the resistance of the LED, circuit, and battery). So with higher voltage cell(s), the flashlight gets brighter and there is no "low light" modes.

The P3D uses a "buck regulator" which can regulate from ~3.7Vf and above (I think around 8 volts was maximum, but 4Sevens has run it as high as 16 volts--no guarantee at that high of voltage). The Buck Regulator can only drop voltage from higher voltage cells to the LED. Below ~Vf, the regulator cannot regulate the voltage (or current). Adding more voltage/cells will not affect the light output (unless the regulator is damaged by an over design voltage condition).

-Bill