Hello, I'm trying to run 3 Ultrafire E17 XM-L T6 flashlights on a 12V 3A adapter. I connected them serially. When I turn the circuit on, they run for about 3 minutes until the rightmost one heats up and closes, it causes others to shut down too. That rightmost one shows as bluish color as others are more yellowish. And others are not heating at all. After it cools down, flashlights turn on again. I tried changing the order, it's always the one on the right(closer to - of power). Do i need to add a resistor to this circuit? How can I solve this problem?
3x Cree XM-L T6 flashlights serial connected powered by 12V 3A adapter - Problem
- Thread starter Shizof
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thijsco19
Newly Enlightened
All of these flashlights have their own driver? That you feed with the 12V adapter?
Since you connected in serie its normal that if the first light in the 'serie' (that one closest to the - *) shuts down the rest shuts down too. The current has to flow trough the first light to get to the next, when the first light stops (due to heat issue) it will act like a switch that is open. That means the current can't flow anymore and when there is no current flowing trough the lights they wont work.
*current flows from the - to the +, that's what you see when you changed the order.
Since you connected in serie its normal that if the first light in the 'serie' (that one closest to the - *) shuts down the rest shuts down too. The current has to flow trough the first light to get to the next, when the first light stops (due to heat issue) it will act like a switch that is open. That means the current can't flow anymore and when there is no current flowing trough the lights they wont work.
*current flows from the - to the +, that's what you see when you changed the order.
Flashlights are intact, I just connected wires to battery connection points. Is there a way to prevent heating of first one?
DIWdiver
Flashlight Enthusiast
I'm very surprised to hear that the overheating depends on where it is in the wiring, not which light head it is. When things are in series, it shouldn't matter what order they are in. When in parallel, it can matter if your wiring isn't heavy enough, but not in series.
Basically, these lights are not designed to work this way. They each want to draw slightly different amount of current. The one that wants the least current (by a little) gets the most voltage (possibly by a lot). It might be counter-intuitive, but this means the one that wants the least power ends up overheating.
You are very lucky that when they overheat they shut down and withstand the 12V. I wouldn't have been surprised if by the time one shut down, it was irreversibly damaged.
One way you might overcome this problem is by adding a zener diode across each light head. A 4.3V, 1 watt diode like the 1N4731 should be available at your favorite electronics parts house, and should do the trick. Just make sure you put the cathode (end marked with the band) to the + side of the light head.
Basically, these lights are not designed to work this way. They each want to draw slightly different amount of current. The one that wants the least current (by a little) gets the most voltage (possibly by a lot). It might be counter-intuitive, but this means the one that wants the least power ends up overheating.
You are very lucky that when they overheat they shut down and withstand the 12V. I wouldn't have been surprised if by the time one shut down, it was irreversibly damaged.
One way you might overcome this problem is by adding a zener diode across each light head. A 4.3V, 1 watt diode like the 1N4731 should be available at your favorite electronics parts house, and should do the trick. Just make sure you put the cathode (end marked with the band) to the + side of the light head.
thijsco19
Newly Enlightened
Thats a good point DIWdiver, I didn't thought about that. :thinking:
Thank you very much! It worked marvelously. No more heating. Everything works perfectly.
DIWdiver
Flashlight Enthusiast
You're welcome. Glad I could help.
