What have I done??

Hi all,

First of all, I should mention that I hate all of you for what I'm turning into. I was perfectly fine and happy with my lights, or lack of them, until I stumbled onto this forum. Now everything is different. Nothing can ever be good enough. With my limited budget, I can only lust after the meduim to high end lights. I am addicted to DX and BessieBenny's cheap light review thread. I need help.
Secondly, I would like to thank everyone for all of the great information here. What fun this is!
Finally, my question: So, I did my first mod. I took one of my Sam's Elements and replaced the Luxeon with a Cree Q5. Even though I'm the world's worst solderer, it went okay. (mostly) and comparing it with the other Element, it is way, way brighter. I also found that I can fit (mostly) an 18650 in place of the 3xAAA holder. So this is perfect. Really bright and with decent rechargeable capacity. But I'm worried. It seems like the Element is direct driven. And it has no heat sinking at all. Zip. The star sits loosely in a plastic holder. It has no contact at all with the body of the flashlight (except through the "-" lead). I've only had it on for a few seconds at a time. Does anyone know what is likely to happen? Situation A: If I go back to 3xAAAs, will the Q5 make more heat than the Luxeon? Cuz that seemed to work fine for 45 minutes or so.
Situation B: If I stay with the 18650, will it provide more current (voltage should be about the same as 3xAAAs, right?) than the 3xAAAs, and thus create more heat?
If everything is direct driven, what determines the current that is drawn?

Thanks again!
mandd

First of all, I should mention that I hate all of you for what I'm turning into. I was perfectly fine and happy with my lights, or lack of them, until I stumbled onto this forum. Now everything is different. Nothing can ever be good enough. With my limited budget, I can only lust after the meduim to high end lights. I am addicted to DX and BessieBenny's cheap light review thread. I need help.

+1

Secondly, I would like to thank everyone for all of the great information here. What fun this is!

+1


Finally, my question: So, I did my first mod. I took one of my Sam's Elements and replaced the Luxeon with a Cree Q5. Even though I'm the world's worst solderer, it went okay. (mostly) and comparing it with the other Element, it is way, way brighter. I also found that I can fit (mostly) an 18650 in place of the 3xAAA holder. So this is perfect. Really bright and with decent rechargeable capacity. But I'm worried. It seems like the Element is direct driven. And it has no heat sinking at all. Zip. The star sits loosely in a plastic holder. It has no contact at all with the body of the flashlight (except through the "-" lead). I've only had it on for a few seconds at a time. Does anyone know what is likely to happen?

Decreased LED life with no heatsinking due to heat damage.

Situation A: If I go back to 3xAAAs, will the Q5 make more heat than the Luxeon? Cuz that seemed to work fine for 45 minutes or so.

Depends on the forward voltage of the emitter. The lower the Vf, the more current it'll consume at a given voltage, and the more heat it'll create. (bad!)

Situation B: If I stay with the 18650, will it provide more current (voltage should be about the same as 3xAAAs, right?) than the 3xAAAs, and thus create more heat?

Voltage-current graphs with LED's look odd. They're like a tan graph (google image it)- start off, increase slowly then increase much faster till it zooms off the top (voltage on the bottom, current on the vertical axis). So, a slight increase in voltage will result in a large increase in current. The good news is a simple resistor will stop the current from causing big time heat problems, the bad news is you'll have to limit current to about 250ma to prevent it getting silly hot. I'd suggest it's a lost cause with no metal to heatsink to, unless you can cram some aluminium foil in there.

:welcome: welcome to this great madness!

Situation A: If the Luxeon handled the heat fine, the Cree should too. AAA batteries can sag a lot under a moderate draw(will depend on the battery), so the battery voltage should drop low enough so as not to degrade the LED too fast.

Situation B: The 18650 battery can handle higher current draw then the AAA batteries while still holding their voltage so it would be bad for the LED to leave the light on for too long.

Neither is recommended but AAA would be less punishing to the LED.

Maybe a piece of right size and shape metal tubing would work as a decent heatsink?

:welcome:

Cheers! Always happy to throw fuel on the fire

Thanks for the welcomes and responses!

I was afraid this wouldn't hold up. I could get a bunch of rechargeable AAAs, but the runtime wouldn't be very good, I suspect. I may try that though.

I was thinking of heat sinking ideas but they (the clever Element engineers) have thought of that too, and pre-emptively thwarted me. The way they have it set up, the back of the star is the positive hookup (with a lead going up to the terminal on top of the star) so if it touches anything...bad news. Amazing. So, I'm thinking of a different way to get the current to the "+" connection. Then I could make something up to do a little heat sinking. But finally, I'd need to limit current I suppose. Can anyone point me to a place to help me figure out what kind of resistance I'd need to add? Do I need to know the exact Vf to figure that out? Wire in series in the "+" line? Sorry for the newbie questions--I've been looking around here a lot, and have picked up a lot of info, but haven't found the great "this is how you mod led lights" thread. If there is one, please point me there and I will be less of a pest.

Thanks again!!
dc

AAA NiMh batteries would give you much better runtime with good output then alkaline batteries.

Vf is the voltage to the LED.

If you can figure out a way to get decent heatsinking, then you probably won't need resistor or driver. With good enough heatsinking, even the 18650 battery would work fine without killing the LED(it would still be pushed pretty hard).

Try having a isolated plastic plate with a spring type thing and solder a wire from the + contact to the spring, then put the thing behind the star. I hope that made some kind of sense.