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I have this with the 5 mode XM-L T6 led in it, and it is VERY BRIGHT!!! (the equivalent of a 1M candlepower spotlight  or a 40W desk lamp) But after a few days playing with it, it started to jump between modes, dim out, flicker etc. occasionally, it would cut out completely Well, I read somewhere a dieing battery causes it. this is not the case. However it does appear the amount of charge in the battery has an impact.

so, me being, ME, I decided to tear apart the torch and diagnose the problem. I looked at the drop-in module... that wasn't the problem. I turned my suspicion to the switch. It seems this was the problem, so I looked around for a replacement, no luck.

my next challenge was to find out how to take apart the tail cap to get to the switch itself.

Step 1: Closer Look Inside

well, I found out how to take the tail cap apart to the point I can see the inner workings. I drew a simple diagram of what I found, and lied them out in order ( the cylindrical spacer goes inside the other washer / toroid shaped spacer)

Step 2: The FIX

I found out is the last piece was not making contact the switch. This turned it to be a very simple fix. just tighten the last part.

Without the special tool that fits in two holes I just used some brute man-power to tighten it and I never had a problem since... if you want to tighter, you can try pointed scissors  or anything that fits into the hole.

please comment, and rate!

Step 3: Improve Preformance of Your Light

Stop by radio shack and pick up thermal paste and smear some on the inside of where the reflector touches the inner casing of the light next to the glass (careful not to get any on though) put the pill (reflector bulb piece) back in there and then shove as many pieces of scrap aluminum foil in around to better help with heat dissipation.

If you are using a cheap Ultrafire, Spiderfire, Trustfire, or some other cheap 18650 battery, replace it with a higher quality battery. It will set you back more than $15, but something like an AW brand 18650 would be worth it because these battery's are of higher quality, last longer, are safer, and crank out more power, (3A or more). Personally, I use Tenergy 2600 mAH. Your light will be brighter and last a bit longer. 

To improve the throw, (the tightness of the beam), get another drop-in or pill with a smooth (SMO) reflector and with a XML-U2, or  (a brighter led bin, a step up from the T6)
<p>Thanks, mines a cheapie that doesnt unscrew but same issue - i just twisted the spring a little bit and presto - solid light...fixed for now.</p>
<p>I also have this flash light and a 3000MAh Ultra fire battery that is really 400 Mah!!!</p><p>However I inherited a Sony laptop which was beyond repair so I broke down the battery pack - 8 neat 2000Mah 18650 batteries, really 2000Mah for nothing - well to me anyway.</p>
<p>I've salvaged many 18650's. I have some that are 15 years old, and work like new. I don't know how that's possible because I think the lifetime of li-ion batteries is supposed to be way shorter than that, but they work extremely well!</p>
Have you tested the capacity of them properly? That is, did you use a device that will place a dummy load (usually constant current, constant power, or constant resistance) across the battery and integrate the current (to track total charge that has flowed) until the battery voltage falls to 2.8V-3.1V, to come up with a AH measure?<br><br>If you have (or make) a good one, it can log voltage and even current over time to allow you to generate a pretty good battery discharge curve. It will start at 4.2V, quickly drop off to 3.8(ish)V, then steadily fall to 3.5V, then start to drop like a rock to zero if you allow it.<br><br>If the load was constant current, it would be easy to take the integral result of the graph (summation of values times the time interval per sample in excel) and multiply it to the set constant current to get a WH measure. For constant power you just need to multiply the time it took to discharge to the power level of discharge, and for resistance, I think you would need to first square all the individual voltage values first in excel, then divide them all by resistance and sum up all the results, based on the P = V^2/R, or in this case, dP = d(V^2)/R or Ptotal = V1^2/R + V2^2/R + V3^2/R + V4^2/R + ... + Vn^2/R. or Ptotal = (V1^2 + V2^2 + V3^2 + V4^2 + ... + Vn^2)/R<br><br>Anyways, sorry of some of that math is confusing, there are a lot of calculus concepts involved here because of the type of data collected.
<p>Nope!</p><p>All I do know is that they last for hours while powering my flashlight, which is really bright. Probably 20 times more than a $1 eBay 18650.</p>
<p>They do work, I'm sure, but they're probably be &gt; half the rated capacity, and ESR will be higher. 30% attenuation is taken to be the point at which something is considered no longer &quot;fit for use&quot; in the industry, this goes for LED, HID, CFL lifespans, as well as for many other things, including battery capacity. Although 30% loss in juice is a perceivable drop, there is still a good about of life in the cell and it will work fine.</p><p>Higher ESR also leads to lower current to the flashlight meaning that it will be dimmer than it should be, but might last marginally longer. I'd say you would expect about 500 lumens initially, a quick drop off to something like 350 lumens, and a gradual fade to darkness after a long time. You might see a small increase in light output with high quality batteries, something like 600 lumens initially, and an increase in endurance as well.</p><p>I know what a difference batteries can make when comparing the light output from a XHP70 LED between 2 old and abused 18650 cells when compared to the much more powerful cells from a quadcopter battery (capable of delivering 0.3KW!!!!) Where I can achieve what appears to be twice the light output from the LiPo. This is with the same <strong>nominal</strong> voltage rating.</p>
<p>For the XHP example, I was comparing 2 old crusty 18650 batteries in series (because my XHP70 is a 6V model) vs a 2S 3000mAH 30C battery, both fully topped off, and both 4.2V open circuit, with the only real difference being the ESR of the cells. The very thin wires used to connect the LED worked as a series resistor to limit the current, as the LiPo would otherwise cook the LED. While using the LiPo, the thin 1ft long 30AWG copper wires overheated too as a result lol!</p>
<p>I forgot to write it, but not all of them work well. Only a small amount of them are really good. It takes me quite a bit of time to check them :)</p><p>I've googled it, and I'm not really sure what ESR means. Is it what makes supercapacitors drain themselves down quickly? (Internal resistance?)</p><p>I don't know if this matters, but I charge them with a $1 18650 battery charger that I bought on eBay. I suppose that it wouldn't have the perfect current and voltage adjusting thingimajigs, but it does the job. </p>
<p>ESR is Equivalent Series Resistance. Not to be confused with leakage current, which causes batteries and capacitors to drain themselves. ESR is the reason why the voltage across a battery sags when you pull a lot of current from it. ESR is caused because the copper foils inside the cell have resistance as well as the terminals and stuff, but the majority is the result of how fast the ions can move through the cell from anode to cathode during discharge, which determines how well it can maintain a EMF, at least for lithium ion cells themselves. The cause is different for different battery technologies but the result is the same. (EMF is just the more correct term for voltage that is &quot;generated&quot; by some means.)</p><p>The cree XM-L LED requires 3A, which is a considerable amount from a single 18650, so the ESR will cause the </p>
<p>Yeah, those ultrafire batteries that come with the lights are just junk. Most often they are old recycled laptop batteries like the ones you got that have been through a lot more abuse throughout their life. I am looking at ordering some new 18650's as my old 2600mAH tenergy batteries are getting old now, and have had a rough life. One of them completely died just last night, The terminal voltage floats at 0V, and it completely open circuit! And I literally mean the battery itself, not due to the protection PCB!</p>
<p>Thanks for this guide, this was exactly the problem i had and your solution worked for me, can't believe it was such a simple fix to do!</p>
<p>Thank you so much! My flashlight was randomly working regardless of power source. Followed your guide, used a pair of hemostats, it took only two minutes. Total success, only if every fix could be this easy and stress free ? Thank you for your help! </p>
<p>Thank you, thank you, thank you!</p><p>I have two of these flashlights and had the same problems from day one. Really thought about returning them but now they are keepers.</p><p>Your find fixed both of mine, however, one of them had paint on the contact area between the spring and LED housing. I scrapped of the paint and done.</p><p>By the way, the perfect tool to use for this is a snap ring puller. I used an old piston ring puller and it was the perfect fit. You can find the tool at any auto parts store. Just get one that has removable tips so you're not getting a single size ring puller. You never know when you'll need to pull a snap ring out of anything.</p>
<p>Great! Glad you were able to save your lights!</p>
<p>Is there a way to get the flash light to only turn off and on instead of going threw all the different choices?</p>
You can remove the module and replace it with a 'one mode' module, but that costs almost as much for the whole thing. If you have some electronics background, you can definitely mod the board to make it one mode, or bypass it all together with a custom 3A LED driver.
<p>My ultrafire XML-T6 Doesn't have threaded washer. What can i do? If Anyone DID Get a new switch. what did you get.? Is there a upgrade? </p>
<p>Disassemble your light down to the smallest components possible and see if you can reverse engineer it some, you might be able to find the problem then. It is hard to say really. I should note that although this method did help me greatly, my ultrafire is starting to prove that it is ultra-unreliable. The switch inside mine (which already had to be replaced once) is starting to fail, and there is a bad high resistance contact inside it causing shorter battery life, and less brightness. It would be cheap to repair it again, I just never got around to it since I do not have a use for it anymore.</p>
<p>What If My XML-T6 Ultrafire doesn't have that ring? and if anyone did get a switch i need details on those.....</p>
<p>Worked great, thanks a lot !</p>
<p>Worked perfectly for my 'flickering' problem. Used a small wire cutter to fit the holes and it worked great. Thank you for a correct diagnosis.</p>
Worked for the head end of my (very similar) &quot;fly wolf knight L12&quot;, too! Thanks!
<p>Great!</p>
<p>I was in the exact same situation and scratching my head wondering how to fix it or where to buy a replacement switch. It fixed mine perfectly. You are the MAN!</p><p>Your drawings were great but I had my iphone out while I fixed mine. Maybe it will help someone to see a photo too. Thanks again!</p>
<p>Great, glad to hear it fixed it!</p>
<p>At last, this problem is solved! Thanks. Now if I can find someone who knose how to eliminate the blinking modes... (my epileptic friends have issues with them)</p>
<p>You can just buy a new drop in 1 module or remove the resistor. </p><p>https://www.youtube.com/watch?v=cr6uEMARdZ0</p>
Getting a new drop in module would be the best solution. They are cheap enough, heck these days just getting half a dozen of these lights is super cheap! You can get them with only one mode (high), 3 modes, and 5 like I did.
<p>Cool! Thank you for that! I thought mine were dying on me :)</p>
You, Sir, are awesome. You just helped me fix my favourite torch in like 5 seconds. THANK YOU.
I made a tool really easily by taking one of the arms off a binder clip and straightening both sides. &nbsp;
Had a faulty switch on my 501b, but this guide helped me sort it! turned out to be a little different internally but i found a misalignment between the tab on the back of the button and the spring to the battery contact. fixed and now works great! thanks!
great! I just wish the Chinese better designed these, i got my light when it was real expensive, I could have bought two maybe even 3 lights for the price I paid for mine, and also, they change the design over time to work better.
I have the same problem with my Ultrafire OSRAM LED torch. It is a pretty unique torch...running 3x16850 side by side. Since it is no longer made, and I would never risk sending it to the manufacturer, I'm stuck with trying to fix it myself. I will give this a try and hope that I don't break the light in the process!
Thanks, mine had the exact same problem and this seemed to fix it!
great! i figred out with mine, this is a temporary fix. to permanitly fix it, i need to solder the switch ciucuit board to the screw/washer part
Thanks for the followup. I noticed a little flickering so I went ahead and soldered mine too, it's been great since. I'm glad, because I spent almost $50 on this light several months ago and it's just been sitting around because I didn't know what to do with it. It was described as putting out 1200 lumens, but I think it's closer to 800. Nice light though, I'm using it as a headlight on my bike.<br><br>One additional tip I noticed: After I soldered, I found that the washer didn't need to be as tight as it did before the solder for it to work. If it was too tight, it started flickering again. I think pressure was being applied to the switch causing it to change modes or get stuck in between them. I backed off the washer a little bit and it burned solid for about 15 minutes, even knocking on it a few times. Good enough for me. Now I just need to see if the battery lasts the whole way through a ride, I'm riding a lot more than I did when I first bought it.

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