I’m planning on wiring multiple XP-E2 red LED’s in parallel. If I choose to use 6 and they pull/take 2A each, that would be 12A. Could I run something like a Samsung 25R? I’d likely run the batteries 2P in order to have some run time. Would I need to run more LED’s to be safe?
That's a good question. It's going to come down to battery sag, but a good cell like the 25R, especially two of them, may not sag enough since the red XP-E2s have such a low vF.
Now, you said that you were thinking about wiring them in series. In that case, I'm assuming that you're also going to run 2S cells. If you run 2S cells maybe you ought to think about just running the emitters in 2S3P with a 7135 driver with 16 chips total. That should get you around 2A per LED without the risk of ruining anything.
1. LEDs don’t pull amps.
Batteries push them. The higher the voltage, the higher the current until they burn out.
2. LEDs in series have the same current passing through them. You don’t add the currents.
The supply voltage needed is the voltage for a given current for the LED times the number of series LEDS.
Oops. I edited the OP, I meant running the LED’s parallel. I had the title correct but wrong in the actual post.
RMM, the low vF is what worries me. That why I may need more that 6 to make sure the battery won’t overpower the LED’s and fry them. It’s kind of a balancing act. I want to use at least 6 LED’s anyway. I need a battery that has a high enough discharge to handle 2A per emitter, but at the same time not give the emitters 3-4A each. .
I'm guessing that with basically 3 red XP-E2s to one 25R they will probably pop, but I've never done it so I can't say for sure. It definitely won't be very efficient with full cells even if it does work.
I may have to do what you were saying and run 4 cells 2S2P and the LED’s 2S3P with a 7135. If I run 20 .350 7135’s that would be 7A. That’s approximately 2.3A per emitter minus the loss through the 7135’s which may pull me closer to 2A. I’m ok with that as I typically run my reds at 2.4A.
Actually I think I confused myself
LED’s wire 2S3P would look like the following crude picture, correct? Running I would assume a Zener modded 7135 driver with 16x .350 7135’s, explain how each LED would get 2A. 16x .350 7135 is 5.6A divided by 3 parallel legs, would be 1.87A per leg right? The LED’s on each leg would pass the current through them so each LED on each leg would be receiving basically 1.87A. Is all of this correct?
Now my original plan was to try to not use a driver and just direct wire the LED’s to the battery with the LED’s in parallel. Out of curiosity, why would this be so inefficient? I do agree that using a driver may be easier, so I am rethinking going driverless and will likely use a driver just to be able to better control current to the LED’s.
your drawing and calculations are correct.
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What is the forward voltage of a red XPE LED at 2A current draw? Another connection option for DD is 3S LED (6.6V) and 2S cells (8.4V)
Running them all parallel direct drive will at least not work with a high drain cell. The red XP-E2 at the desired 2A has a voltage of 2.9V (link) , take e.g. the SonyVTC5 (link), even at 30A the voltage is well over 2.9V, so even 15 red XP-E2's parallel will get more than 2A, and the battery is not going to like the constant high drain. Then take a non high drain common used cell, the NCR18650B (link), it is only tested up to 5A, but at that current well over 2.9V. It might work with say 6 red XP-E2's parallel, but the cell will then deliver more current than it is designed for, not a very stable situation.
Conclusion, as above: find a way to regulate the current.
Yeah, it’ll have to be regulated. I was trying to keep it simple, but doesn’t look like that is going to happen. The problem now is how to wire 2S3P with the LED’s in a big ring and I can’t run wire across the middle of the ring. It’s gonna take some planning.