With the introduction of yet another 3x XML light - the Sunwayman T60CS with the 3x 18650 cells in series - and the rumored near release of the Zebralight S6330 with 3x 18650 cells reportedly each driving an individual XML LED, I am wondering if there is any consistency in how the XML LEDs are wired in these 3x XML lights. Are the 3x LEDs in series or parallel (maybe with a low ohmage resistor balancing outputs), or individually driven (as per the S6330)?
Why do I ask? I am becoming more susceptible to lumen inflation - most specifically the 2000+ lumen lights which are primarily based on 3x LEDs. Production (in)consistencies concern me. The associated cost of these lights tends to preclude experimentation purchases. Differences between multiple LEDs at high output are nearly unmeasurable by most of us. and some would say, an ignorable problem. well, maybe not. Have there been any reported aging problems with any brand 3x XML light?
Understood that the method of wiring the LEDs is closely related to how they are driven - current or PWM. Wiring the LEDs in series or parallel represents a design challenge for consistent output per LED. Either that or Cree has a very impressive production control! However the battery voltages from the battery pack design also vary widely, yet another challenge for the LED driver(s). FWIW, I read reports on CPF of some TM11s having some LEDs dim or dead or flickering w/o affecting the other LEDS. I have not noticed that any other brand 3x XML light has been reported as having this problem.
Last edited by moldyoldy; 08-05-2012 at 03:58 PM.
From what I have seen on the light lights I've opened and worked on they are generally attached in series. If you think about it that makes sense to. LEDs are current driven and may all have a different Vf for the same current. If you drive 3 LEDs in parallel the varying Vf's may produce varying results. If you drive them in series with a constant current driver then the Vf just becomes the sum of the 3 LEDs.
If they're run in series they're probably going to be fairly fairly similar in brightness, within the binning tolerances ~7%.
If they're run in parallel with appropriate resistors, they should also be pretty similar, but in that case the manufacture of the lights may want to measure the LED's vf and bin them together.
Also, the LEDs are very durable, it's unlikely that one of them will wear out appreciably faster than the other.
I'm not sure how PWM or constant current would have anything to do with this.
So I'm just not seeing a problem at all, I don't know anything about those faulty TM11s but I doubt it has anything to do with the LEDs, why do you think this may be a problem?
a problem? I was not sure, but noticed that several design solutions were being used and was curious why. Although I am interested in the 2000+ Lumen lights, my retirement disposable income does not allow much experimentation any more. Waiting is always an option...