# Luxeon Star at 9 volts?

#### Slick

##### Flashlight Enthusiast
I have this "big idea" that might not be too smart since I'm severly lacking in electronic expertize.... but here goes.

I bought a Coleman AA (green aluminum) specifically to mount a LS/o in. The battery compartment has three internal ribs that can be easily machined out to take three CR123 lithium batteries for a total of 9 volts. The whole light is quite modular and looks to be a decent candidate for this type of mod. Obviously I will need to use a resistor or circut to limit power to the Luxeon Star.

Not being an electrical engineer, I am uncertain whether this would best be achieved through a speciality circut or if I could use a formula to determine the appropriate resistor to put in the circut..

Would using a resistor conserve battery power, or just bleed it off as heat? Is there a "model" circut that I could build that would limit current efficiently? Perhaps there's a simple circut that would effectively halve the current down to 4.5v ?

My goal is to build a flashlight that is incredibly bright and has an enhanced run-time versus a 2 AA (3 volt setup).

Or am I just searching for the "holy grail"? Any suggestions or advice would be greatly appreciated!

#### Coherence

##### Newly Enlightened
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>...batteries for a total of 9 volts...Obviously I will need to use a resistor or circut to limit power to the Luxeon Star.<HR></BLOCKQUOTE>

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Would using a resistor conserve battery power, or just bleed it off as heat?
<HR></BLOCKQUOTE>

The power dissipated by the resistor(s) is released as heat.
However, by increasing the resistance in the circuit you will decrease the current flow, and 'conserve' your battery power (since the circuit is using less power now). So yes to both questions

Here is a post I wrote about calculating resistor values.

I think that you want something better than just resistors if you want to run it bright.

Try looking for a 'buck' type DC-DC converter.

TWO WORDS:

I wouldn't

#### Slick

##### Flashlight Enthusiast
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Silviron:
TWO WORDS:

I wouldn't
<HR></BLOCKQUOTE>

Could you be a bit more specific? What do you see as the difficulty or problem?

Obviously resisting current down from 9v would seem wasteful. My hope was that there would be a circut that I could use to cut power effectively to half - 4.5v and do it with out incurring some major loss. And, at 4.5v it would seem that it would run twice as long.

Why do I want to do this? Well, the Coleman light will easily accept three CR123 Lithiums in place of the original two AA's with some machine work. Can you say "pocket full a Kryptonite"?

Aside from all that the flashlight is a really nice piece that would lend itself to doing a luxeon mod.. It's nicely machined, thin aluminum that looks like it would sink heat like crazy. The shortcoming is that the tailswitch looks cheezy and will not support momentary contact - it's either on or off. So come on guys.. lets chat about some ideas as to why or WHYNOT this will or won't work.

And if I come up dry, I just guess I'll have to build something with the Luxeon for the mainbeam and throw an array of wide-angle Nichia whites on the perimeter to soak up that extra power that's on board..

#### Silviron

##### Flashlight Enthusiast
The light you have envisioned WOULD be really neat, but I wouldnt do it for a few reasons:

COST- 123s are just too expensive for the minimal light and longevity they would give you with a LS. Of course if you are rich, this doesn't matter.

EFFICIENCY- Step-down converters waste even more energy than resistoring. I've built a couple of lights using one of the more efficient step down converters and was not at all happy with the longevity, even running off of multiple D cells:
http://www.national.com/pf/LM/LM3477.html and when the batteries are drained by only about 30% you are in the dark. You don't get hours of dim on any of the step down regulators that I know of.

The Coleman light IS really nice for LED mods, (I just built one using a lambertian red/orange LS and it absolutely "kicks butt" on just 2AAs) and some of the folks here have done some real nice mods with them using the 2621 National step-up switchers, and maybe the Zetex circuits, and they give good performance on cheap AAs.

Actually, your idea of using the Nichias to drain off the extra voltage may be a good idea, but I'm not enough of an expert to say how efficient it would be.

If I were going to do a 3X 123 on one, I think I'd do an incandescent- you could make a "poor-mans" Surefire or streamlight out of one.

Just my opinion on this- others may have different experience or opinions.

#### Slick

##### Flashlight Enthusiast
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Silviron:
EFFICIENCY- Step-down converters waste even more energy than resistoring. I've built a couple of lights using one of the more efficient step down converters and was not at all happy with the longevity, even running off of multiple D cells:
http://www.national.com/pf/LM/LM3477.html and when the batteries are drained by only about 30% you are in the dark. You don't get hours of dim on any of the step down regulators that I know of.
<HR></BLOCKQUOTE>

Many thanks for the detailed reply, Silviron.. this is exactly want I wanted to know, but obviously not hear
It's just that I really hate seeing such a FAT battery compartment go to waste
..

I've been thinking about it and as for trying it with a Nichia array, I think it would work but pull current hard enough to make runs times undesirably short. If I try it, I'll set it up (on the bench) with 6 Nichias (to start) and check current draw then run time.

#### PsycoBob[Q2]

##### Enlightened
Might be easier just to make a ZLT-LithiumAA light. With 1.5v lithiums, battery life would be great, and likely cheaper than 123's on a per-hour basis.

You could always try to use a pair of 3.6v lithums and a ZLT, by putting a small piece of double-sided copper-clad PCB inbetween the batts, and running them in parallel..... if you feel a huge urge to mod it.

#### Silviron

##### Flashlight Enthusiast
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Slick:
Many thanks Silviron for the detailed reply.. .. It's just that I really hate seeing such a FAT battery compartment go to waste .... set it up (on the bench) with 6 Nichias and check current draw and run time.<HR></BLOCKQUOTE>

You are welcome!

I had a similar thought as far as the big battery compartment, although I was thinking more along the lines of using 3X 2/3A NiMH rechargables in there. I may try that myself eventually. Would sure be a lot cheaper to run than with 123s.

Your six Nichia array - 3X 123 idea might make a reasonable light- run 3 parallel X 2 series; that would not burn up a fortune in battteries, although it would be more expensive than similar options.

#### Slick

##### Flashlight Enthusiast
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by PsycoBob[Q2]:
You could always try to use a pair of 3.6v lithums and a ZLT, by putting a small piece of double-sided copper-clad PCB inbetween the batts, and running them in parallel..... if you feel a huge urge to mod it.<HR></BLOCKQUOTE>

There's actually enough room (if the ribs are fully machined out) to hold a battery tray AND the lithiums in paralel, Hmmmm....
->

(photo swiped from the lightsite)

+ the LS and step-up circut should still fit in the head with a bit more work.. now to find some thin tubular stock to fashion a battery tray maybe? Hmmmm...

It's probably still gonna be a lot of extra time and expense (not to mention the \$ batteries) to step up to the 123's..
At least I've decided that it's getting the LS anyways