14500 and SSC direct drive ok?

Is it ok to direct drive an SSC Emitter with a 14500 battery?
I am thinking about doing this in a flashlight I have but do not want to burn out the emitter. If I need to put a resistor in to make it safe, what rating resistor?

I've tested a SSC direct drive on one 2400 mAh 18650-cell. With a big copper heatsink it drew about 1.2 amp.. Seemed not to give any problems !

To push it to the limit, right now I have a heavy heatsinked torch with a SSC operating at 1.56 amps !! Have played with that one for days now.. Still works fine..

So I think I am allowed to say: No problem, but you need provide some heavy copper heatsinking to keep things on the safe side..

If you're not shure, you can always use a 2 ohm 1/4watt resistor to decrease power a bit..

Its always a good idea to test things first, and measure the Amp-draw.. Propery heatsinked, the SSC can easily cope with up to 1 Amp.


Regards,

Ra.

Ra said:

I've tested a SSC direct drive on one 2400 mAh 18650-cell. With a big copper heatsink it drew about 1.2 amp.. Seemed not to give any problems !

To push it to the limit, right now I have a heavy heatsinked torch with a SSC operating at 1.56 amps !! Have played with that one for days now.. Still works fine..

So I think I am allowed to say: No problem, but at least provide some heavy copper heatsinking to keep things on the safe side..

If you're not shure, you can always use a 2 ohm 1/4watt resistor to decrease power a bit..

Click to expand...

I think 1/4 watt may not be a high enough wattage resistor. If that thing draws say 700mA fresh that's 1 watt dissipated in the resistor. I would go for a 1-Ohm, 1-Watt resistor. Also, It would be a good idea to keep the resistor separate from the LED if possible so that there won't be as much heat buildup right in the same place.

Keep in mind that the efficiency of the LED goes down the harder you drive it.

I wonder if it might be actually more efficient to use a small resistor than none.

Unless these are a completely different animal from a LS for some unknown reason, it depends on the forward voltage of your emitter(which will also affect how much current it draws in direct drive).
What is the bin?

It is a 'U' bin LED from DX.

Yeah, the Vf will effect how long it should happily live driven direct.

Having said that, I have a QIII with a TW0H that's been in it for well over a year. It pulls just under an amp with an R123 cell. I've run it several times all the way through a charge cycle and have probably put 30+ charge cycles through it and I feel it's at least 95% as bright right now as it was when I built it. I just swapped the star and added some Ceramique around the heatsink/body joint.

I'm not offering this as advice, but sometimes, those stars can really take a thumping.

2xTrinity said:

I think 1/4 watt may not be a high enough wattage resistor. If that thing draws say 700mA fresh that's 1 watt dissipated in the resistor. I would go for a 1-Ohm, 1-Watt resistor. Also, It would be a good idea to keep the resistor separate from the LED if possible so that there won't be as much heat buildup right in the same place.

Click to expand...

1 watt dissipated in the resistor would mean a voltage drop of about 1.42 volts over the resistor (at 700mA)!! A single cell produces about 4.0 volts tops..
Do you want to tell me that the forward V of the led at 700mA equals 4-1.42 = 2.58 Volts !!

No way!! In my book, the emitter needs more like 3.6 volts to operate at 700mA.. In that case 4.0-3.6=0.4 volts is applied to the resistor: That means 0.28 watts is dissipated in the resistor, not 1 watt...

Please tell me if I'm wrong here !!


Regards,

Ra.