Luxeon Star Mod Using Single AA...

Wonder if it is do-able? Not using your father's 1.5V alkaline AA weakling, but the 3.6V lithium AA. If heatsinking issues could be addressed (after all, it's not like the LS would really be overdriven), one would have a Very Small, yet rather bright LS mod. But which platform to use...

What about 2 lambda circuits in series...

Maybe a CMG dimfinity body could be used - then build a custom head to house a bare Luxeon emitter? Run time would probably suck tho..

Back on 4-25-02 I did a test of a 3.6vdc Li battery in the single aa battery holder of my SLS. After one hour the 3.6vdc battery generates enough light to read by and the color was very green. The SLS was very warm to the touch! After resting for 10 minutes, it was generating about the same amount of light as at the 30 minute mark. Seem to indicate to me that the 3.6vdc Li battery is ok to use for short (2-5 minutes) periods of time.

Pardon my ignorance, but what is it with "heatsinking"? Is this a problem where the heat effects the battery or what?

Thanks!

Heat is wasted energy! Batteries lose capaticity and LED's don't shine as bright and change color.

Heat is a problem for the LS itself. It becomes less efficient and puts out less light (while still burning the same amount of battery power) as it gets hotter. If it gets too hot it destroys the LS.

- Russ

Okay, so by using a heat sink, you are doing what?

Again, thanks for the answers!

A heat sink is used to take heat AWAY from the LED. The more surface area on the heat sink , the more heat that can be disipated.

Ah! I understand now! Perhaps I need to read up on all this stuff. Since I came into this forum, I realize how uninformed about a lot of things I really am. You all have been very helpful! Thank you!

Orion,

The LS is different from incandescent lights with respect to heat. Light output from incandescents is dependent on voltage and current with heat as a PRODUCT of heating a wire to produce light. With the LS light output is dependent on voltage and current with heat as a PRODUCT & FACTOR of light output (edited). Light is being produced directly at the junction of the LED and junction temperature should be kept as low as possible. The specs for the LS show operation primarily at 25 degrees Celsius (junction temperature) and light output is considered 100% at that temperature (arbitrary values). Colder temperatures than that show light outputs higher than 100%! I have seen specs at Mark Hannah Surplus. www.markhannahsurplus.com

I've said all this to say that in cool or cold weather all our LS's should be exceedingly bright compared to warm weather! You will notice other threads on CPF showing the possible need to use lithium batteries in very cold climates. I'm sure that's a trial and error thing about needing lith's.

Anyway, keeping an LS cool is important for light output AND long life!

The 3.6 V AA lithium is weaker than Mr. Bulk's father's Alkaline 1.5 V AA. It is only designed to put our a max of 20 mA or so and is happiest at < 2 mA.

An LS will not be happy at 20 mA.

Hmmm, then it seems Father Knew Best...

I did a fairly extensive test on running a LS off of 3.6V Tadrian AA lithium batteries, and posted much of the resuls here.

Results were FAR better than expected, given the manufacturers recommendations.

These batteries are far from being a perfect solution for running a LS, but they WILL do it- about equivalent to running an ARC LS on the single AA holder as far as initial brightness, but with longer overall life even though they start to dim a little faster..
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They are extremely useful in running one or two Nichias....I built my Mother a little single AA mod using a blue-green Nichia in a 75 cent plastic AA keychain flashlight....

It has kind of a stiff switch and her arthritic hands can't turn it on and off, so she just leaves it on continuously.... Over three weeks of constantly being on so far, and it is still bright enough for her nightly voyages to the bathroom.

Thread with tests is at

http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=6&t=000138

Silviron -- I'm surprised by your report. I remember reading someone's report that a 3.6 V AA ran for < 1 hour in his ARC LSS.

I do agree that the 3.6 AA's are very bright with 2 cells and 2 LEDs. They also seem to last a very long time in 3 or 4 cell 4 LED configurations with resistors.

On another topic, have you found the voltage drop on the 4/3 A NiMH cells you purchased from American Scientific to be as relatively impressive compared to AA NiMH and A NiMH cells as I have? I have set two of my DB8AA's up with 6 serial 4/3 A's and a recharger port through which I measure voltage under operation. The difference is increasingly significant as load increases -- up to 150 millivolts at 3.35 A.

I haven't tried it myself (ARC LS on a single Tadrian AA), and I'm sure Gransee would be able to give a better answer, but here is my GUESS:

The ARC converter circuitry is going to suck even MORE current out of the battery than the straight LS does- As the battery tries to provide what the circuit wants, it is depleted faster- it just can't keep up.

Whereas, the LS led itself is just happy to accept whatever the battery is willing to give up.

The ARC circuitry shuts off when it doesn't get the power it wants, but the straight LS will still be glowing enough to read by WEEKS later, happily (but dimly) operating on around 2V at 7ma.

When the "power supply" gets that low, however, if you turn it off it may not start back up without a little extra "juice" but once it gets going again, it will keep running ---

I never documented it, and the factory specs set a much higher cutoff point, but I'm pretty sure that I have had LSs running on less than 1V several times, but when I checked it with the meter, THAT drew enough of the current to shut down the LED. Let the battery sit for a couple of days and it will start the LS up again, be pretty bright for a second, then drop to just a glow.

As far as your other question on the 4/3A NiMHs- I'm not *really* sure what you are asking, but here has been my experience:

So far I've only finished 3 lights with them (built 5 but destroyed 2 of them because of carelessness in the last few steps) Two of them are my CPLS models (3/4" copper pipe, 3X 4/3A batteries.) One with white and one with cyan LED. Plus I have also built an 8AA DB modded into a 6 X 4/3A (2 Parallel X 3 serial) with a white LS.

The Cyan CPLS really *Kicks Butt*, putting out an incredible 707 / 170,000 LUX (1 meter / contact with sensor) with a fresh charge. Four hours later, it is still putting out 519 / 125,000 LUX. but after 4 hours it starts falling off rapidly, and after 8 hours I'm only getting 76 / 16,430 LUX and it is usually "dead" after 10 - 12 hours. I was actually hoping for greater longevity, although the brightrness is double what I expected.

The white CPLS is less bright by far- only about 300 LUX initially, not much brighter than an ARC LS (I may have "over resistored" it). Similar discharge curve to the cyan CPLS. Again, I was a bit disappointed in the longevity.

Both of them get WAY too hot with continuous operation from a fresh charge- after 15 minutes or so, they make a good handwarmer for the winter, and are just about reaching their max. allowable junction temp (estimated). I've actually kept them in the freezer for the first couple of hours between measurements. Probably ought to paint them black to help bleed off some extra heat.

The DB Mod is my favorite mod so far, although it has not been fully tested- ~415 LUX @ 1 meter to start, nice white beam in the center, SLIGHT pea-green corona, but the best "throw" of any of the LED lights I've made or bought. Have only run it for an hour or so at a time a couple of times, and not much of a brightness drop.

Silviron:

I think I understand your comments on the LS vs. ARC LS. Thanks.

Re the 4/3 A, I had posted the following voltage drop measurements running 4 different W/A bulbs with current of 1.1A, 1.42A, 1.95A, and 3.35A with various freshly charged the day before 4-cell NiMH and NiCad configurations. Thus, surface charge was eliminated from the equation.

As an example, at 3.35 A the 4/3 A's still delivered 1.00 V while the AA's and A's only delivered about 0.85 A and 0.87 amps, respectively. This suggests particularly low internal resistance which seems to be consistent with the thermal runaway you experienced with your LS.

Oh, I see-

I hadn't been able to measure that in the CPLSs because they were sealed once finished, and I can only test the voltage through the recharge jack now. During construction, I never measured voltage and current at the same time to notice.

At full charge, three of them in series almost always measure 4.23V (no load)and 4.02 - 4.17V under the load of an LS with a ~1 ohm resistor. I can't find any notes with it written down what current they are pullling, although I seem to remember one pulling 850ma and another pulling 1.1 Amps off a fresh charge.

I think the CPLS white is using 3800mah batteries that I had left over from rebuilding my laptop battery, so it is probably 10%-20% higher capacity than most of those from American Science & Surplus.

I am a new dummy here. Apparently this Luxeon Star is a very bright light. How bright in comparison to what incandescent light I might have???? Lets compare it to my Underwater Kinetics SL-4 (4 C cells) which is about as bright as my 4 D cell MagLight.
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