Hello, everyone. I am really new to this forum and even newer to led flashlights. I have read and really tried to find answers to what I going to ask now. I bought my first led XM-L T6 flashlight a few months ago and I can’t stop with these flashlights I now have about 20 of these, some that take 26650, 18650 cr123.Some are single cell some take 2 batteries and one 12 led flashlight that takes 3 26650 or 3 18650 rechargeable li-ion. I have bought chargers, soldering iron, led emitters, drivers and have tried to do mods which I know nothing so I have destroyed them. Let me get to my questions. I want to fix one XM-L T6 flashlight that stopped ( I know I could buy another flashlight for less that its costing me to fix this but I want to learn ) working it takes 2 18650 batteries. I think the driver that came with it does not work anymore when I took it apart both wires came off from driver. I tried to solder back on ( I not very good at soldering) the wires where I saw + and - but I think I put too much solder maybe something got solder touching where it should not be anyway I bought a new cree xml t6 led emitter tested it with a 18650 battery and it turned on fine then I tried with 2 18650 batteries connected to driver ( the one I tried to solder the wires) it burned out my emitter. Correct me if I am wrong but you need a driver if you use 2 18650 batteries but not if you use one. I did take a single cell 18650 flashlight and remove the driver and put it back together and it worked fine and I think its brighter. Last night I took a flashlight that the emitter broke ( my fault ) this emitter led was have the size of any other ones I have bought from EB I guess someone is getting cheap and was not very bright and it takes 1 18650 battery I took one of my new emitters 20mm,led twice the size of the other one and it was a 16mm od. I took the new emitter that would not fit into the pill so I dremel tool and made it fit pill soldered it to its driver and flashlight works brighter than when it was new. So that worked but back to my issue first is there a way to test driver I took solder off and resolder it a little cleaner but I afraid to try a new emitter. Here is the big question I think I need a driver that has that little coil on it to use 2 18650 would that be a 8.4 driver? I read somewhere that that you may use the cheaper ( no coil on it) with 2 batteries is this true. When I do a search for driver for 2 18650 I find a driver with that coil ( coil way bigger than the one it came with and they want 12 to 15 dollars? The old driver and emitter are both 20mm I guess that’s what I need to replace. Hope some can help this confused old man. Oh by the way I wanted a thrower and read about Yezl Y3 I bought it and its bright and a good thrower very nice flashlight. Thank you
When you remove the driver, you are “direct driving” the LED, which is why they are brighter than before; they are getting all that the battery can provide, only regulated by the resistance in the wires, & the battery itself. You will also run into excessive heat problems, particularly if you use good quality batteries.
As you have discovered, you can only Direct Drive from one 4.2v battery. Hooking up two batteries in series will be too much voltage for a single (XML) LED. This sounds like what has happened when you tried to repair the two-cell light driver.
Drivers that can handle two or more cells into one LED are referred to as ‘Buck’ drivers, & typically have the windings on them as you have noted.
This thread lists some high-power drivers for single XML’s.
Oh - welcome to BLF 
There are a few common LED emitters. Smaller ones aren’t Cree XM-L. You can identify an led by comparing it to pictures. http://flashlightwiki.com/Cree
You might want to bookmark LEDs and other stuff as well. There’s a ton to learn and plenty of other threads to bookmark but keep reading and asking questions and you’ll soon be up to speed.
First off, welcome to the loony bin. You’re among friends! We’re not polite or kind or courteous or any of that other effete crap, but we love each other and our differences make us all stronger. You’ll like it here.
Next, take a breath. The easiest way to troubleshoot complex systems is by focusing on the simple bits. The big stuff usually works itself out. You haven’t done anything wrong, but that first post has a lot to process…
Now, the bad news is, the only way to really test a driver is to install it & apply power. That’s where a good dose of crazy helps! But that’s fine. You’ll see.
You bought a lot of tools and parts!!! That level of commitment can’t go unpunished! :bigsmile: Let’s get you using them effectively first, shall we?
Speaking of seeing… Can you see the wee solder joints you’re making, perfectly? To put it into different terms, you should be able to see a .5mm pencil line well enough to take a razor blade & split it in half. Close-enough is good-enough, but that’s how I can express the concept in writing. You don’t seem to have much trouble in that area, for a “confused old man”, so I’ll just leave that out there.
Lastly for now, nobody can solder for you. You have to do that. Here’s how I can help you do that: Go get any old crap-ass toy with a circuit board in it. Make sure the board has the wee gold dots for soldering and testing!! Trash everything but the board. Get some wire & tin it, then remove all the solder you can from it. When it’s clean, try to get to where you can then add a wee ball of solder JUST to the VERY END of the wire, and make the ball ~exactly the diameter of the wire. When it doesn’t work right, stop doing it wrong. When it does work right, clip the end off, start over. And over. Until your brains fall out on the floor. When you can leave your wires prepped with the greatest of ease, remember how you did it & make sure you practice, practice, practice.
Side note: Practice does NOT make “perfect”!! Practice simply makes “PERMANENT”. Only PERFECT PRACTICE MAKES PERFECT. So practice the perfect ones and forget the bad ones. Don’t make a big deal of it, but this is half the skill you’ll need, so YBTJ of what’s “enough” practice.
Now take your salvaged junk PCB and practice soldering all those wire ends you just tinned & loaded onto whatever little solder pad you can find. Over and over and over again. Until your brains fall out on the floor. Then sleep and do it all again tomorrow.
Why, you ask? You mentioned it.
Here comes the toughlove: No one can do your soldering for you. It’s on you to KNOW when you’ve made a good joint & when not to apply power. No, looks alone are not enough, but usually when a joint “looks good”, it will be. Best news: There is no such thing as a perfect solder joint! So don’t worry about it, just make it stick and flow to both pieces, without blobbing all over everything else.
And don’t spend that much for drivers!
YBTJ, but here’s a $5.59 one you might like.
Here’s a $7.97 one for variety.
Lastly, here comes the boom. I will do your soldering for you. Lately it occurred to me, that I can share my talent & it helps me. I offer to fix your dead soldier for you, and shoot a detailed Macro record & write up what & how I did it for a post herein. This helps me by letting me get a free look at Yet Another Possible Next Dimbo’s Torch, but without the risk of it being a POS. Not to brag, but to me, the “work” involved is “as easy as”, so don’t think I’m sacrificing anything! In the end, you get a working torch with a detailed tutorial for all on how to fix whatever went wrong. It will only cost you the postage both ways and any parts I may need. Weird, huh? Obviously I’d sign a Note to assure you’d get it back as soon as I got it fixed — I’d not want to keep it!!
So that’s my wall of words. My advice is to check your solder joints, put the thing together and hang on! Just keep paying close attention to the details, the better to Perfect your Practice.
Dim