Another question.... If an LEDs firing voltage is 3.7 volts (2.8 A of course). Does that mean it is at its brightest at 3.7 volts or if you overdrive to, lets say, 4.5 volts, will it be brighter??? (I know heat could be an issue). Oh, also, what is the critical temperature for LED failure?

The first light I built, I just put a battery pack together (4.8v charges to 5.3) and it fired. However, the driver is rated for 5.5-8 volts. Problem is that once the 4.8 volt battery pack gets into the low 4's (about 1 hour), the LED will flicker a bit. I need a higher voltage on the driver. Now, the single mode driver is rated at 2.7-4.5 volts, making my 8AA LED pack better suited for it.

I have a power supply coming to try this out, but I figured I'd ask.

The LED will be rated at a particular amperage. In this case its 2.8 The Vf or Foward Voltage is the voltage required to get this amperage. If you increase the voltage you will increase the amperage. You will also increase the brightness and heat and decrease the life expectancy of the LED. But you will soon get to a point where the extra voltage gets turned into heat and not brightness.

look at this pagehere
and you can see what I mean. from 1400ma to 2000ma you get very little more lumens and even at 1400 lumens you will decrease the life expectancy a great deal. But hey if it drops from 100,000 hours to 1000 hours who really cares right?

With the three mode driver, the lumens get noticeably brighter from the 4.8 volt battery pack to a 6 volt. From the 6 volt to a 7.2, doesn't seem like much... As I mentioned earlier the 3-mode shows to be good from 5.5 to 8 volts. Get much lower than 4.7 and the LED will flicker a bit and the three modes won't work. I am ready for my power supply to come in to do some further testing.

In the meantime I am headed to Florida to do some caves tomorrow through Sunday.
Thanks

Have fun in the caves.

This power supply, is it adjustable voltage? If so can you hook it up to your driver and LED and tell me what happens when you dial down the voltage?

At what voltage does it go into low volt warning?
At what voltage does it turn off?

OK Packhorse, I finally got back here and read your post. Here it is:
1. The lower the voltage, the lower the amps and very very dim.
2. I don't know about low volt warning, did not get one...
3. The LED actually fires at 2.2V (extremely dim). At that voltage, the power supply registers 0 amps. After the driver, you get 2.33 V at 0 amps.
4. Anything lower than 2.2 volts is off.

5. Extra information- At a power supply setting of 5.7V, the power supply puts out approx 3100mA. The voltage after the driver is 3.4 volts and current approx 3100 mA.
At power supply setting of 2800mA, the voltage is about 5.5V and themA is 2800. Extremely small difference in brightness is noticed at the 2800 mA.

All readings taken on the single mode driver. The 3-mode driver took 5.4 volts to get 2800mA out to the LED. After the driver, the voltage was 3.2 V at 2800mA. So, somewhat similar in performance.

Hope that helps, let me know if you need anything else.

My light performed very well, however, I need a different battery pack, the 8AA pack makes the light flicker a bit after 37 minutes. I will try 6D cells for 6Volts and see how that works. I compared it to my 21W Salvo LED and it holds its own against it. Overall not bad at all.