Six-LED headlamp for mountain climbing

How to modify bulb headlamp to 6-LED which lights for 3 - 4 hours continuously with 4 AA batteries

I cannot find 6-LED headlamp in my area so I need to modify the bulb headlamp to use LED lights. I have spent many hours figuring out the LED circuit diagram that powers six white LEDs off a 6V battery pack (four 1.5V AA's in series). From my experience, the circuit diagram proves to work for white LEDs of the same specifications using only one resistor of 6.8 ohms. The life span of LED will be shorten with high current which in my case is 50 mA to attain maximum brightness but not to get LED burnt in 5 hours. This LED arrangement works because of the same colour of LED otherwise I have to solder a resistor to each LED.

LEDs wired in parallel

How this works is that while every LED receives the same amount of voltage, the current of the source is dispersed between the LEDs. What this means for you is that you have 6 LEDs paralleled off a battery, it's going to drain the battery a lot quicker than if you only had 3 LEDs in parallel. However, LED has much lower power consumption than filament bulbs. Four AA rechargable batteries can last only 1.5 hours for 4.8V Kryton bulbs but for 6-LED, it can lasts for 3-4 hours and pretty good for camping and mountain trekking.

Pictures of my modified headlamp using 6-LED

Current limiting resistor calculator

Some values to try:

As Supply voltage:
From 3, 6 and 12 volts

As LED forward voltages:
Red and green; 2 volts
Blue and white; 3.5 - 4 volts

.:Leds in parallel

Several leds connected parallel with one resistor

LED calculator thanks to Japala: http://www.metku.net

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