Powering Seoul P4 with 3 NiMh

[oger]

I wonder if it is a good idea and possible to connect a Seoul P4 directly to 3 Nimh or NiCd cells.
The low forward voltage (3.2 - 3.6V) should make this possible.
Of course I would still need a resistor (specially selected for each LED) to limit current.

 

[rscanady]

One thing to keep in mind is that the Voltage -Current curve for this LED is very steep between 3 and 4 volts (look at datasheet), and that NiMH hot off the charger is are around 1.4 volts (x3 gives 4.2 volts, 3,6 volts nominal ). YOu can use OHM's law to get a rough approximation of resistor needed. V=IR, so R= V/I.

R=4.0V/.350A = 1.4 ohms if you want to drive it around stock, now this doesnt take into account resistance of the host you are using and other things, but its a good place to start.

Hope this helps,

Ryan

 

[EngrPaul]

I have a few flashlights that are direct drive from 3AA batteries or 1 RCR-123 3.6V.

They all stabilize on an current based on the internal resistance of the battery and the wiring of the flashlight without the addition of a resistor.

For instance, I just measured 1500 mA direct drive on a VINET with a P4, using a RCR-123 right off the charger (about 4.2V). I am comfortable with this, because I usually use low mode and only flip to high for a short time. However the maximum continuous current is rated at 1000 mA. Driving to 1500 mA does not create a tint shift problem, and I have it well heat-sinked. My only potential concern will be reduced life of the emitter. If I cared, I might use a resistor.

I'd suggest putting the emitter in the flashlight, and momentarily drive it direct using an ammeter. See what the current is. It might actually be below 1000mA with 3AAA, because their resistance goes up more with current demand compared to a RCR-123. I know my Brinkmann 3AA is direct drive, and to a Luxeon or Cree it is only around 550 mA.

 

[ace0001a]

I was able to carefully pluck the Lux1 emitter off its star on my Dorcy Metal Gear, AA and solder an SSC P4 to it, remove the 1 ohm resistor on the internal cicuit board and then put it back together. What I got was probably the brightest Metal Gear I've ever had. EngrPaul is right though as 3AAA flashlight battery holders usually put out around 500-600mA with NiMHs. So far my SSCP4 Metal Gear is working fine...