Need battery coaching

First of all, I am a Noob here at the forum and I have to say some of the nicest folks run and participate in this forum.

Now a question: Can someone explain to me why LED flashlights illuminate more if you use rechargeagle RCR123 batteries instead of the surefire normal batteries? specifically, the surefire lamps. Someone wrote about unprotected batteries delivering more voltage to the 3 watt LED's. Does this jeopardize the flashlights design in any way or the bulb life?

Any comments or suggestions most appreciated.

It's simply because the rechargable batteries have a chemistry that provide more power. A RCR123 is 3.7V while a CR123 is 3.0V. Supposing they both provide the same current the higher voltage would mean it provides more power.

Short answer: Most RCR123 cells have a fully-charged voltage of about 4.1x V no-load and can supply around 3.5V under moderate load. A 'normal' Surefire or other CR123 cell has a no-load voltage of 3.3V new and can supply around 2.5V under most flashlight loads.

More volts to the LED or bulb means brighter. Note that some LED lights use circuitry between that cells and the LED to control or regulate voltage, current, or power to the LED. Higher than 'normal' voltage into the circuitry may make no difference to the LED, or the circuit may behave differently based on that higher-than-normal supply voltage. The different behavior may be a brighter LED, or a burned out circuit or LED.

Thanks guys for the replies...Mike, I have a new K2 Kroma arriving soon, do you think it will harm it if I use protected RCR123A rechargeables? I'm concern about the 4.2 volts damaging the circuit or LED bulb. I would not want to experiment with the light.

I have no idea of the consequences of using RCR123 cells with a K2 Kroma. Maybe someone else can answer that question.