Troy, your Ill Pill Answer on Lithiums is Here

Troy asked "As soon as Lambda gets my money order,I will be recieving a mini mag modded with an ill pill.I have decided to go with a tailcap switch on this light,and was wondering if there was a way to increase the heat sinking on the mod so I can run lithiums in it.I was thinking some thermal epoxy or something since I wont need to turn the head to switch the light on.So..Lambda or anyone else,what would be the best way to do this?
thanks,
troy "

Answer:

Using lithiums in the Pill mod is not recommended, even if you were to thremal bond the pill in to the battery tube, and the head to the battery tube. The Pill is based on using regular alkiline AA cells, as to not generate too much heat.

Even using lithiums in the Illuminator, which uses an aluminum heatsink bonded to the head and battery tube, produces some very warm results. Mr. Bulk reported that the Illuminator got too hot to handle comfortably after about 30min using liths.

Lithiums start with a higher initial voltage than alkilines, and maintain a higher voltage for a longer time.

The Illuminator circuit is most inefficient at the higher voltage, increasing in efficiency as the voltage drops. This helps extend normal battery life, as regular batteries drop down from their initial voltage pretty fast, and spend most of their life at 70% initial voltage and below.

So using lithiums not only severly overdrives the Luxeon (making it real hot), but also runs the converter at it's most inefficient voltage range for a longer time. The result is a lot more heat gets produced by both the Luxeon and converter than with alkilines.

It's like putting 130 octang gas in your car, it has more power, but also gets real hot as the fuel is still burning when the valves open. The result is a lot more heat, and possible burnt valves. The engine would have to be redesigned to run on that gas, but then would perform poorly on regular gas as a result.

That's why I don't recommend liths in the Pill, as it was simply not designed for that kind of heat. While it may take it, how long becomes the question.

A 2AA flashlight can only disipate so much heat so fast. How much and how fast depends a lot on the environment, ie. room temperature where it is used. The Pill will start out with fresh alkiline batteries running ~3watts, but within a few minutes will be running ~1.5watts, with less than 10% change in output. Using liths will maintain that ~3watt power usage for less than 10% gain in light output, and generate significantly higher temps.

I really don't understand everyone's desire to use expensive liths, but if there's enough interest, I could look into a "Lithium Series" converter optimized for those batteries, but then it won't work so well with alkilines.

I hope I've explained this so everyone can understand why Lithiums are not recommended in the IllPill. The IllPill uses minimal heatsinking (heavy copper clad pc board) to retain the original on/off function, as the whole converter 'floats' up and down in the battery tube. Even replacing the converter top pcb with an aluminaum heatsink will not improve the thermal path from Luxeon to flashlight enough for use with lithiums. Even the Illuminator with it's fixed, thick, well bonded heatsink is marginal for use with lithiums, as the converter design was for the voltage discharge curve of alkilines, so lithiums generate a lot more heat, than more light.

So, comments everyone? Is there interest in a "Lithium Series" converter optimized for those batteries? And if so, tell me why lithium use is so important to you to justify the price difference.

The only reason I'd use Lithiums in one is to keep in my car. (Very cold here in the Winter), but for that purpose alone, my Brinkmann LX would do just fine with a MagPill (If/When I get one) on my belt. If you make a Lithium version though, I'd buy one.

I don't know why I really want to use use lithiums in my flashlights.It must be all that extra cash I have lying around


I didn't realize that the circitry was optimized for alkalines.I use lithiums in my Arc LS,and I like the way it lightens up the flashlight with a 2 aa pack.Plus it is quite a bit brighter.I was under the impression that the reason you couldn't use liths in a pill mod was because the pill floated in the tube.I figured with a tailswitch,I could bond it to the tube and it would be a poor man's LI.Now I see that lithiums are not really recommended for that mod either.

The Illuminator was not much brighter (I think 30 lux max) on AA liths. And I was shocked at the price ($5 for two???) but bought'em to do a run time test. As it turns out the Illuminator was getting way too hot way too fast, and prior posts I had read seem to indicate that you don't get that much more light over 4 volts (DD) anyway, although I don't know how sucha scenario plays out with a circuit board in between.

But to the casual naked eye the liths didn't make the Lambda any brighter, so by using these significantly more expensive batteries you'd receive:

1) no useful increase in light output

2) definitely no increase in extended run time (gets too hot)

3) possibility of permanent damage if left on, whether intentionally or accidentally, by cooking the LS.

Thank you Mr. Bulk for some real world input on this subject.

Everyone always wants lith batteries for the cold weather, as they maintain a higher voltage. They just need to realize that this is not an ordinary flashlight, and with the Il circuit, even good alkilines at -20F will have enough to fire up the circuit, and if left on will self warm in few minutes, going to full brightness.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by lambda:
And if so, tell me why lithium use is so important to you to justify the price difference.<HR></BLOCKQUOTE>

Long shelf life. You can stick them in a drawer (or earthquake/flood/huricane/tornato kit) and when you need them they will work.

-john

Would I want a "lithium series"?

Not being funny here, but that would all depend upon if you told me that it was a good idea!

If you could design a Lambda Illuminator, for example, that was optimized for Lithiums, and I could benefit with the results of either a Significantly BRIGHTER OUTPUT, AND/OR a longer run time, I would be interested.

I would only be a little interested, if it ONLY offered me a longer run time. For my purposes, I can change batteries, but some people really want that long run time.

I would be MORE interested, if it offered brighter light, and the same run time.

and,

I would be MOST interested, if it offered both brighter light, and longer run time.

One of the benefits of using a light like what you design, with the intellegent electronics, is that you don't have to get the absolutely best battery for the light to work the best.

So yes, a lithium series would be nice, but there would have to be some benefit.

ON THE OTHER HAND . . .

Now, let me ask you this, would it be possible to make an "extreme brightness" circut for regular alkline's, at the expense of a shorter run time?

Here is my thinking. I paid 10.00 for 4 Energizer Lithium AA batteries. From what I have read, that is about what they sell for, and you are not going to find too many discounts from that price.

Now I also paid about 12.00 for 24 Energizer Max on sale, and you can regularly get Rayovac maximimum or Kirkland Costco batteries at about 10.00 or so for 24 AA's.

Now I don't know this for a fact, but, for the same price, I would bet that 24 Energizer Max would last longer than 4 Energizer Lithium batteries, in almost any situation.

That is 2 sets of batteries, vs 12 sets of batteries. Does one set of lithium batteries last 6 times as long as one set of Alkline's?

If I could get the absoulte maximum brightness out of a Lambda Illuminator, with a run time of 60-90 minutes (more is always better), and I had to change batteries more often, I think that I would go for that.

I would like to see a sudden, noticable drop in the light output when the limit is reached. That way, I really know when it it time to change the batteries. I was as happy as a pig in mud using your Lambda Illuminator, and didn't even realise that the batteries were almost dead. Those LED's can fool you by still putting out the ultra white light.

I can always throw a couple of extra AA's in my pocket.

So, I guess we would have to see the cost/benefit of extreme brightness with lithiums vs alkline's with regard to run time.