Help fixing a cheapo 18650 flashlight

xdriver

Newly Enlightened
Joined
Oct 8, 2010
Messages
27
I have a cheap $20 fandyfire 502B single mode china light that uses a single 18650 battery and a XM - LT6 cree that is labeled 3.7-4.2 volts on the reflector. For some reason (yes, I know it is cheap china), the first time I turned it on the light went on for 5 seconds and then off and I can not get it to work. I have tried taking the battery and simply putting it to the +/- part of the springs and it does not work (circumvented the tube and tail switch). The 18650 is charged and reads 4 volts with my volt meter. If I quickly touch a 9 volt to the +/- the light will go on. What is the issue here and what can I do short of sending it back (the seller will take it and pay for it but I figured if I can fix it it will give me a challenge and I won't have to hassle with the post office. Thanks folks.
 

RBWNY

Enlightened
Joined
Mar 10, 2011
Messages
374
I'll (try to) refrain from the usual cliches that questions of this sort usually receive. Since I'm not an "electrical wiz" my experiences with similar issues have been to clean the threads, shoot a little De-oxIT into the bezel electronics...pray...and try again. Short of that making any difference, "you got what you paid for"... a piece of junk! (see, I said I'd try :ironic:) Anyway, unless you're too insulted to trust anything else I can suggest... I would send it back. The driver may have toasted itself, or just be plain faulty. It can't be that the cell was too much for it, so it's got to be bad electrics..........unless you can try a different cell. What is the battery its using? Is it a button-top? Perhaps it's not making proper contact? Gee.... maybe I CAN be of help after all!

Anyway, good luck.... and do yourself a favor....DON'T buy ANY more lights with "FIRE" in the name that aren't SUREfire!
 
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lightfooted

Flashlight Enthusiast
Joined
May 6, 2010
Messages
1,017
Well upon doing a Google search I found a comment on the DX site that there was a problem initially with the tailcap o-ring...might wanna check that out. However that may be pointless now that you have applied your 9 volt battery to a lamp that is specifically rated for no more than 4.2 volts. Honestly I am wondering why you would do that...but that's all under the bridge now. Hopefully it was a brief enough exposure that all of the components are still intact and have not melted and will function fine. Did you try powering another light or device with the same battery and not just testing it with a Voltmeter? It's possible that the problem may also be on the driver board, a loose solder connection or something.
 

xdriver

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Joined
Oct 8, 2010
Messages
27
I did try other batteries and I also circumvented the tail switch and tube altogether as to rule those parts out. The first thing I always try to do with something like this is to remove the unneeded components like the switch, tube, reflector, in this particular case.
 

Fireclaw18

Flashlight Enthusiast
Joined
Mar 16, 2011
Messages
2,408
Given that it lights with a 9v, but not with a 4v 18650, I suspect a defective driver rather than a connection issue. Your best bet is probably to just return the light unless you want to try your hand at modding and replace the driver.
 

HotWire

Flashlight Enthusiast
Joined
Mar 9, 2011
Messages
1,651
You've probably done all the things suggested here. I had a similar problem with a Chinese "T6 XML" flashlight and a ****Fire battery. I found that when I used a good 18650 battery with the same 4.20v the light worked. I recommend AW, Redilast, and Callie's Kustom batteries. Well made and will last you a long time. Never apply more voltage to an LED than it is rated for. You'll kill it!
 
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