14500 and SSC direct drive ok?

[davenlei]

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?

 

[Ra]

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.

 

[2xTrinity]

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..

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.

 

[Vermonter73]

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.

 

[Owen]

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?

 

[davenlei]

It is a 'U' bin LED from DX.

 

[cratz2]

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.

 

[Ra]

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.

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.