how to test a led

Hi chaps.
bought a 8watt led torch from qualitychinagoods, it uses 1x18650 batts.
anyways tried the battery(fully charged) and nothing.
so i tried 2xcr123 (3.7v) in it and it lit for a split second.
my question........ have i damaged the led or is something else going on.
is there a way to test the led to see if i have damaged it???

cheers axbol

axbol said:

Hi chaps.
bought a 8watt led torch from qualitychinagoods, it uses 1x18650 batts.
anyways tried the battery(fully charged) and nothing.
so i tried 2xcr123 (3.7v) in it and it lit for a split second.
my question........ have i damaged the led or is something else going on.
is there a way to test the led to see if i have damaged it???

Click to expand...

I'm assuming this is of the same construction as the Golston 7W which is plausible to me as most of the 7-16W variants seem to be very similar.

If you unscrew the head end and pop off the plastic cover over the LED star giving a view like this


Just arrange a couple of wires from a suitable battery and touch them to the appropriate contact pads - the positive pad is connected by a red wire and the negative by a screw here. There should be + and - marks on the star. It is fiddly to get the wires to contact and holding devices are a great help.

If the LED is alive, you WILL know as the glare dazzles you.

If the light was designed to use a single 3.7 volt cell from the get go, then you may have fried the LED when you applied twice as much voltage (2 x 3.7 volt rechargeable CR123 sized cells = 7.4 volts) to it.

Just how bright was the LED when it lit for a split second?

Only use a single battery when testing the LED directly. Fingers crossed.

cheers matey. tried your test and nothing. looks like i fried it then?

is there anywhere i can get a replacement led for this torch????


cheers axbol

Sorry to hear that Axbol.

You can find plenty of replacement Lux 3 stars over in the Dealer's Corner area of CPF.

You did check polarity on the LED? I know you almost certainly did, but just in case try the wires the other way round.

Just about anything mounted on a star will fit. You will need to fiddle with the resistance - see the Golston 7W threads for how to get the thing apart and replace the resistor. If the resistance (measured from the body to the + contact on the LED star) is about 3.5 ohms then it should be happy with the Luxeon 3 of your choice and 2 RCR123's. This is a hefty overdrive but the "7W" clone LEDs in the Golstons seem to tolerate it.

A star mounted K2 might give more light (and more heat) but would almost certainly need different resistance.

thanks for the replys chaps. i've also got a k2 torch, and if i test it on the continuity test the star actually lights up. not well up on led's yet, but suppose you live and learn. the new torch is deffo fried. wanted it to go hunting tonight but suppose i'll stick with the k2 for the meantime. i actually bought the 18650 battery and charger thinking it would fit the k2 but the batteries to fat. i've got a lot to learn.


cheers axbol

If the K2 body is the same as the 8W one, there's plenty of metal there so it can easily be bored out. Or alternatively, get a dead laptop battery pack - Older Toshibas use 17670's which will fit in an unbored body. They will almost certainly fit in the charger too, though they can be a tight fit.

If the torch is designed for 2 RCR123, you will get about a quarter of the light running from a single cell.

can anyone tell me what the resistors look like or where they are (pics would be appreciated) too much info on searching the threads

cheers axbol

This http://candlepowerforums.com/vb/showpost.php?p=1327712&postcount=255 may help and from post 413 http://candlepowerforums.com/vb/showpost.php?p=1419738&postcount=413 on in the same thread.

This http://candlepowerforums.com/vb/showthread.php?t=103057&page=14&pp=30 will take you there.

Hopefully the resistor will measure something sensible so you won't have to go in there which will simplify matters.

Good luck with it