Marathon light

No; not a flashlight that you take on a race but a flashlight that keeps going and going and...

Would a 2 'D' cell single LED flashlight last approximately 20 days with good electronic regulation?

How long could you stretch a 2 D cell power supply with PWM and persistence of vision tricks? (also possible use of lower power LEDs like amber or RED for REALLY long runtimes.)

I don't have any particular use for this idea, it just seems neat.

Also where could I find some good meathods of calculating runtimes, my current system is botched together with guesswork. (I want accurate universal forumulas)

does such a flashlight exist already? (no I've seen the PAL/hummer light)

The Eternalight projects runtime up to 1200 hours on its lowest setting. That's 1 of 4 LEDs lit, pwm, and persistence of vision (i.e. noticeable strobing). That's with 3 AA batteries. It's still a useful amount of light but I find the strobing annoying. However, the next higher setting is still claimed at 1000 hours and the pwm is tighter with no noticeable flickering. To get a 2D value just multiply by the ratio of amp-hour capacities between 2D cells and the Eternalite's 3 AA cells. At this low of a current drain that should be a good estimate. Actually, 3 D vs. 3 AAA might be more reasonable; I'm not sure but more conversion losses might be required to drive with only 3 volts suppplied.

The other side of the coin for extreme runtimes is, what do you consider "useful" light? I haven't run the thing for a full 40 days straight to see what's left (I *have* run it all night several nights in a row and didn't even make a dent in the batteries). LEDs will bravely keep putting out light even if there's only a whisper of power left -- whether it's a useful amount is up to you.

Melchior said:

No; not a flashlight that you take on a race but a flashlight that keeps going and going and...

Would a 2 'D' cell single LED flashlight last approximately 20 days with good electronic regulation?

How long could you stretch a 2 D cell power supply with PWM and persistence of vision tricks? (also possible use of lower power LEDs like amber or RED for REALLY long runtimes.)

I don't have any particular use for this idea, it just seems neat.

Also where could I find some good meathods of calculating runtimes, my current system is botched together with guesswork. (I want accurate universal forumulas)

does such a flashlight exist already? (no I've seen the PAL/hummer light)

Click to expand...

A 6D mag with a downboy and a 5mm of some sort would probably last forever.

I bring a 4 AA 5 LED Craftsman light. it' s bright enuf and I haven't had to change that batteries yet with many many hours of use. Good all around light

whats the runtime estimate for a walmart 6V lantern with a single led conversion ?

9v batteries are pathetic in terms of energy storage, yet these guys claim to have gotten 1 year of continuous illumination ---

http://www.9voltlight.com/testing

Imagine how long that thing would run on 6 D-cells

Nubo said:

9v batteries are pathetic in terms of energy storage, yet these guys claim to have gotten 1 year of continuous illumination ---

http://www.9voltlight.com/testing

Imagine how long that thing would run on 6 D-cells

Click to expand...

I have one of the original Palights and it's good for two years on a nine volt.
It's usable within a very narrow range for that term.

Melchior said:

Would a 2 'D' cell single LED flashlight last approximately 20 days with good electronic regulation? does such a flashlight exist already?

Click to expand...

It could probably be done. The tests on my light from Modamag were stopped after some 48 hours. Note this uses six AA cells and has a FatMan & Pot and
3x Luxeon TW0J.

At the lowest setting it puts out a very usable light.

For a single 6V Lantern with 1 white LED:
1,500 hours give or take a couple 100. (my very rough estimate w/resistor style stepdown)

Roughly TWO months. That is getting abit silly if you ask me, at a minimum you should have 3 or more LEDs for any ammount of useful light (epecially for large flood type lights).

Also these numbers may be very inaccurate. (I just hurl them into my spreadsheet and it spits out the hours)

Does anyone know where you can get DIP charge pumps?

They are usually more efficient than Inductor type designs right?