I accidentally damaged the drive of a KD C8 xml. I put the wrong reflector which shorted the connections of the driver.
But I think/hope the led is still good, as it does light up low even with the damaged(?) driver.
While waiting for a hypothetical replacement driver to show up, can I just direct drive the emitter?
Is it safe, or do I risk damaging the emitter?
Its an XML-U2 I think.
It’s most likely okay, the resistance in the spring and wires will drop the current to safe levels at 3-5A.
Make sure you have good heatsinking for the LED as well.
To try it out, use a discharged cell at 3.6V and check if the current is at reasonable levels.
I converted one of my C8 to direct drive, no problems with cheap cells. Put an IMR from a powertool pull HERE and light went bright to dim in a few seconds. I checked the current draw, it was pulling over 7A. I caught it in time, no damage. Oh yes, I had removed the spring on the driver beforehand.
What do you mean by remove the spring from the driver. how will it make contact thus?
Is it ok to use cells from laptop battery packs for direct drive?
Use a normal li-ion (not IMR) and you’ll be fine. I direct-drive a few of my XML and XRE light and they’re all doing well.
They’ll probably not reach their 50,000 hours lifetime but they’ll be obsolete by then anyway.
Generally you’ll get close to 4A on standard setup, and closer to 5A with thick wires/braids. (NOT RECOMMENDED, not worth the lumens gain, unless you do full copper setup).
Tsetse if you will give us the exact cell you will be using we could give you a close estimate. Direct drive really depends on the cell being used and the resistance in the host and the led used. A quality cell will give higher currents than cheap china cells. IMR cells can supply loads of current. Really need to know the cell being used in direct drive to give you a estimate.
I tried it with a sanyo laptop pull. Good news the LED is still ok and shine all bright.
Bad news the solder iron decided that it was time to die. Time to get a new crappy iron.
The direct drive C8 tops at 1.5A, while I get 1.8A on another C8 with the same battery.
What am I doing wrong?
Sounds like a difference between resistance in the host and vf of the led. You can’t cheat I = V / R ohms law.
The laptop pull maybe old and tired and not able to give that much current, because of the high internal resistance.
You would have to try a new quality cell to be sure or a discharge test would have to be preformed on the laptop pull to tell you how it holds its voltage under load.
Hi,
I’m assuming that you’re using a DMM to measure tailcap current? If so, try to use different, heavier leads from the meter to the C8 body and to the battery negative end. Some people here use solid (not stranded) 14 AWG wire (in the U.S., Romex) for their meter leads when testing tailcap currents. I haven’t tried that, but my understanding is you just strip the ends of the solid Romex wire and shove them into the jacks in the DMM.
Wow… I did exactly what you said and now I get 3.8 A on the direct drive and … 4.5A on the KD C8 using the same Samsung ICR Laptop battery pull.
I am impressed, but still do not understand why the direct drive is not pulling more than the one with a driver.
Leads have so much resistance?
I’ve noticed that, that the leads make a big difference, not just in the meter leads, but elsewhere (driver to emitter, battery to driver).
When I first started, I kind of “pooh-poohed” that notion, but I had one driver I was testing, that was suppose to be a 3 amp driver, and I was getting sub 2 amps. Then, I kept improving the leads (driver to emitter and battery to driver - this was outside a light) and eventually got emitter current to about 2.85 amps by doing that. Now, I believe that :)…
EDIT: I don’t know why the KD C8 would be pulling more amps that the direct drive. How did you direct drive? Also, maybe different emiitters draw different current?