Surefire Bulbs, General Rule

Is there a general rule when to change batteries? I remember reading in previous threads that when the batteries are low, it can damage a Surefire incandescent bulb. Is this still true? Since incandescent Surefires are generally not regulated, I figure the light dims almost immediately after turning it on. At what point should I be swapping batteries? This is referencence to my Surefire 6Ps with 65 lumen lamp, and Surefire C3 with 91 lumen lamp.


(in my LED lights, I let the batteries run all the way down).

I have always changed the batteries when the light is no longer as bright as I know it can be [on fresh batteries]
Sometimes I notice this sooner then other times... I am a real white light junkie which means I go through batteries perhaps faster than most other people.

Al

So, like for a 60 minute runtime bulb should I change the batteries at around 30 minutes to be safe? I can see some change in brightness around 20 minutes, but to me that seems too excessive to change it that soon?

i do not see how a weak batt could damage a bulb, over voltage sure, but under? if this is a problem i also would like to know. any info would be appreciated thanks in advance. /ubbthreads/images/graemlins/smile.gif

The more 123 fueled LED lights you have the earlier you can swap out the aging and decrepit 2.98 VDCs for fresh ones. I can see the light yellowing easily myself in my G2/P61, and its run time is 20 minutes but it is a bright 20 minutes. I usually swap em out around 10 to 12 Op hours and the old ones go in the arcs,streamlites and dorcys. I do always run fresh in my TW4 to have all the horsepower available in my EDC. As for damaging the bulb with low voltage,it is for real!!! If the wire doesnt get hot enough the vapor deposits don't re-vaporize and build up on the bulb, when you see the bulb darkening it's due to running it with low voltage and it won't be putting out its spec lumens again.

30 minutes in out of rated 60 minutes is perhaps too soon - especially if you don't use it constant-on so much...
However, I go by the light quality not by the minutes.

Ever since I started out getting interested in flashlights I have been under the impression that powering SureFires with dieing or dead batteries would promote the discolouration of the bulb. Since this has only happened for me on a couple of lamps that I have done extensive runtime testing on, I conclude that using fresh SF123As in my lights and changing out the batteries earlier rather than later is helping.

Al

cool thanks for the info, i was not aware that underpowering a bulb could be damaging. i will make sure to keep an eye on beam quality from now on. /ubbthreads/images/graemlins/thumbsup.gif

This subject keeps popping up. Information gleaned from lamp manufacturer's sites indicates that low voltage will not shorten a lamp's life. YMMV.

[ QUOTE ]
jayflash said:
Information gleaned from lamp manufacturer's sites indicates that low voltage will not shorten a lamp's life.

[/ QUOTE ]

Could you direct me to some sites that provide this information? I used to work with some really high-power lamp manufacturers (2kW lamps), and they imposed strict power supply requirements for just the reasons smokinbasser stated - basically, if you underpower the lamp, the wall temperatures get too low, and the halogen cycle is interrupted, leading to blackening and premature failure. Of course, the lamps I was dealing with were much larger than standard flashlight lamps, so perhaps underpowering a smaller bulb still sufficiently heats the quartz (or glass) enclosure. However, I have never seen this type of information provided on lamp manufacturer sites. For example, the WA site states that:

"[C]ooling [the lamp] will not extend lamp life and may cause the lamp to darken prematurely."

I'd be interested in reading what other miniature lamp manufacturers have to say on this topic, so any pointers would be appreciated.

Thanks!

John

Try this site: http://vsg.cape.com/~pbaum/halogen.htm refer to light dimming.

I can't remember other sites right now but I'll keep scratching my head. Keep in mind that at lower voltages the tungsten doesn't boil off as readily. It's also said that operating the lamp at normal temperatures for a few minutes will recombine any tungsten, that has been deposited on the globe envelope, back to the filament.

I wish this controversial topic would get settled. I've yet to experience rapid darkening of my xenon lamps, some not run with fresh cells. My vacuum lamps do darken, but that's with FRESH cells.

Different people seem to have had varied results, so I don't know if it's the result of different lamps or methods of observation.

Another note: cooling is much different than operating at lower voltage. WA states longer life can be expected by running at a lower voltage.

I have an old 6p, which I retired 3 months age, in 8 years of service it has had two lamps, the current lamp is 4+ years. I drain batteries until there almost exhausted (60+ minutes). No problems here. So, my general rule is 60 minutes.

Thanks for the link. Makes sense that less tungsten evaporation occurs at lower power, and that this may counter the reduced halogen cycle efficiency. But the question then becomes at what level of underdrive is the tipping point reached (where bulb life actually is shortened)? The information in the link you provided seems to indicate that underdrive will almost never lead to blackening failure:

"Modern tungsten halogen lamps continue the cycle to power points (55%) so low that the tungsten evaporation rate is insignificant in terms of blackening."

and

"Lamps are designed to control the cycle, so that nominal lamp life is always (roughly) obtained, however the lamp is dimmed."

It's that "however the lamp is dimmed" that seems to fly in the face of my experience and with recommendations from other lamp manufacturers. But then again, I haven't really used modern halogen flashlight lamps at undervoltage conditions. The original 6p (round) that I used to have was hardly used due to the cost of batteries, and my Scorpion was hardly used due to the rubber coating. And all the incans I play with now are rather overdriven, and therefore exhibit different sorts of failure modes.

Arrgh. I wish there was a definitive answer on this issue also. In the immortal words of Unfrozen Caveman Lawyer, "My primitive mind can't grasp these concepts." Perhaps we should try to get one of the Carley engineers on chat one of these days.

If you are specifically asking about Surefire lamps, then I would say don't worry about it. As far as I know, Surefire doesn't use a Halogen lamp in the P-series, therefore no Halogen cycle to break. In fact, just looking at the website it doesn't look like they use Halogen lamps in any lights they make, just Xenon, which is a Noble gas.

Personally, I use my 123s as long as the light 'feels' bright enough. I avoid comparing used cells to fresh ones, because I'll always want to dump the old cells if I do that. I haven't noticed yellowing or darkening of my G2s or Scorpion.

That I'm aware, SureFire's Lamps are high pressure Xenon Halogen mix.
To quote Dr John Matthews from his article on SureFire.com -
"...lamps can be run at very high temperatures by filling the lamp envelope with xenon gas at high pressure and by incorporating a halogen additive to the mixture. This, of course, is what is done with the high-performance lamps used in SureFire flashlights..."

Al

It was explained to me that the risk in running the batteries way down is that the vaporized tungsten doesn't redeposit onto the filament as efficiently as with new batteries. So, when you finally put in fresh batteries after running the previous set way down, the filament isn't at "full strength" due to some of the tungsten still residing on the glass and the lamp blows from the full power of the new batteries being applied to the weakened filament.

When I bought my first Surefire, a 6P, back in the early 90's I was used to maglites and such. 123's were very expensive back then so naturally I ran the first set all the way down to get my money's worth. When I finally replaced the batteries, the lamp blew instantly when I turned it on. I called Surefire to buy a new lamp (not knowing the price of a Surefire lamp /ubbthreads/images/graemlins/faint.gif) and to find out why it didn't last and they explained the above to me. They also sent me a free lamp. /ubbthreads/images/graemlins/thumbsup.gif

Talk about it, forgot to change my batts even though I just reminded myself by posting here, damn, last night some guys' cheapo china led's beam beat up my P60. I really should have carry spare batts...

You went head to head with someone else carrying a light without carrying reloads? /ubbthreads/images/graemlins/tongue.gif

May we prescribe a SC1.. /ubbthreads/images/graemlins/grinser2.gif

I'm surprised the P60 didn't run out of gas in short order. Usually the end comes pretty quick for those lights, the thing dims, gives you a few extra minutes and then won't come back up, at least my P60 does that.

Mine too, but I think it varies a bit from bulb to bulb, mine have about 10 minutes or so of orange dim light like a mini mag.

Mine only have about 2 to 5 seconds of yellow light









until I turn them off and grab another light /ubbthreads/images/graemlins/grinser2.gif