Drive Levels vs Heat

Ive recently got very worried about damaging my lights.

Most of my lights, on high, are at LEAST 700ma...

and they all will get hot if left on for too long. Regardless whether your hand is there or not.

The problem with this, is i end up using them intermitently in situations where i really need the light. All my lights, have gotten really hot when i used them over a period of time.

I am just wondering, is this potentially harmful to the driver? i know it degrades LEDs over time.

and, what kind of lumen or drive levels can i set, for example, my LF2X, and put its diffuser on, and just leave it as an area light and not worry about ti blowing up or something.?

Crenshaw

The only heat related driver failure I've heard of is a 7135 based driver getting so hot the solder melted. The light started flickering, so the owner hit the head and this knocked the 7135's off the board completely and the light died. IMO the driver should be fine.

As for optimal drive level, do some experimenting!

how much light do you need? 140 lumin enough ? i just recieved the DX HF-19 Cree Q2-WC sku.13928 much to my suprise and delight it does run for 4 hours continuous with an 18650 cell and unlike most of my lights runs no more than lukewarm. liked it so much have ordered afew more, it is a loose copy of the solarforce L2 type, just wish i could get the dropin that comes with it on there own.

Wolf359 said:

how much light do you need? 140 lumin enough ? i just recieved the DX HF-19 Cree Q2-WC sku.13928 much to my suprise and delight it does run for 4 hours continuous with an 18650 cell and unlike most of my lights runs no more than lukewarm. liked it so much have ordered afew more, it is a loose copy of the solarforce L2 type, just wish i could get the dropin that comes with it on there own.

Click to expand...

the problem is that, just cos you dont feel heat, doesnt mean it isnt there, there just might be a very poor thermal pathway....so none of the heats getting trasfered to the outer casing....not sure about the DX light though.

I havnt had any heat related problems so far...just worried..

Crenshaw

ok run it for 10 minutes and popped out the dropin into my hand and it is lukewarm.

Glad to see someone else has the same thoughts. I also like to use a light for area lighting and when you get up to 700ma the heat does get pretty intense. I also find myself using lower settings if available on the light so as not to get things so hot. I find when using a flashlight in candle mode and bouncing the light off the ceiling that a base of 60 lumens is pretty adequate for basic tasks but not enough to read or do tasks requiring precision or intricacy. You can actually get by on much less than 60 with adapted eyes but like you said you find yourself wanting more. The nice thing about todays Leds is anything up to 80 lumens or so and there doesnt seem to be serious heat and you get pretty good runtimes even off an RCR123. But having 100 + lumens and not getting excessive heat would be great . Maybe withing the next cpl years we will be there but I cant afford to keep up with this technology anymore. So though I used to always want the brightest output possible I know find myself seeking lower more efficient drive levels for better runtime and less wear/tear on the LE

I also wonder how much heat batteries like RCR123s can take before they also start to suffer and degrade. On some of my lights if I leave them on high tailstanding they get VERY hot to the touch and I am thinking my expensive AW RCRs are cooking like eggs in there and the result is premature loss of capacity and charge . I mean , most electronic devices I can think of utilizing Lion rechargeables (cell phones,Nintendos,cameras etc) do not push batteries or create huge amounts of heat like a flashlight does. I wonder if RCRs were really designed for platforms like flashlights or have been pushed into this type of service.

*hijack*

Should a li-ion heat up on it's own? I noticed this in one of my lights where I'd used a couple of wraps of paper to stop a 18650 rattling- when I took it out, it was surprisingly warm, I'm guessing because it wasn't conducting it's heat away to the battery tube.

litetube said:

I also wonder how much heat batteries like RCR123s can take before they also start to suffer and degrade. On some of my lights if I leave them on high tailstanding they get VERY hot to the touch and I am thinking my expensive AW RCRs are cooking like eggs in there and the result is premature loss of capacity and charge

Click to expand...

*hijack*

Should a li-ion heat up on it's own? I noticed this in one of my lights where I'd used a couple of wraps of paper to stop a 18650 rattling- when I took it out, it was surprisingly warm, I'm guessing because it wasn't conducting it's heat away to the battery tube.

Based on specs, Li-ion secondaries can be charged in the temp range from -40C to 60C, and discharged in the temp range from -40C to 65C. Similarly, cycle life doesn't seem to be adversely affected in tests at 21C vs 45C for discharge rates ranging from 0.2C to 1.0C.

I have a 6P modded to flupic that gives 1 A to the led at max.
As this is not some crappy insert without heat path, but a very massive block of Alum. I mounted the Cree on, the light gives its heat to the outside very quick.
--> within 5 mins noticeable heat at the head
--> 10 mins for max heat.

max heat without cooling (mounted on bike bars, or hold in hand) means just hot enough to be gripped with bare hand = 55-60 deg. C.
Thats totally ok and the light has run for at least 100 hours (at full power) from April last year when I built it. Yet noone had a brighter single emitter here, so the led, if degraded, did not degrade too much

at 700 the light must be some very small 1 CR123 light to get this hot - if it ever gets hot.
wondering :thinking:

If I know I will be in a situation that I need light for a continuous length of time, I will bring two lights to switch when each one gets warm. But if I get stuck in a situation where I only have my EDC, I will use it on the medium setting.

DX 6090 - 600mA @ 6v for approx 80 lumens
Malkoff M60LL - 170mA @ 6v for approx 80 lumens

I know this is not scientific, but you can guess which one runs cooler and longer... with similar output.

roymail said:

DX 6090 - 600mA @ 6v for approx 80 lumens
Malkoff M60LL - 170mA @ 6v for approx 80 lumens

I know this is not scientific, but you can guess which one runs cooler and longer... with similar output.

Click to expand...

Something is way wrong with that 6090 if it's only putting out 80lm.

roymail said:

DX 6090 - 600mA @ 6v for approx 80 lumens
Malkoff M60LL - 170mA @ 6v for approx 80 lumens

I know this is not scientific, but you can guess which one runs cooler and longer... with similar output.

Click to expand...

Aren't P4's rated 80-87 lm at 350mA?

I think your math is wrong.

One thing I noticed with my 4th gen VB-16 is that you have to feed it a lot of ma's to get just a little more light.The drive level of this light is 700 ma on high(at the emitter).If you turn it down to 550ma it makes almost as much light.Most of my romisen lights drive the led at a moderate level(450 ma to 600 ma) and they only get warm.It seems that most leds make a lot of light at 750ish ma and not much heat.Push it to 1000 ma and you get a little more light and a lot more heat.There must be a graph on this somewhere.This is just an observation on my part and YMMV.
DON

roymail said:

DX 6090 - 600mA @ 6v for approx 80 lumens
Malkoff M60LL - 170mA @ 6v for approx 80 lumens

I know this is not scientific, but you can guess which one runs cooler and longer... with similar output.

Click to expand...

i dont think thats really possible?

even presuming its a P4 its got to b at least hitting 137 lumens based on the ma...even a P2 would still probably hit around there..

and Q5s cant get 80lumens from 170ma

don, i think thats called diminishing returns? thinking
as in, once you get past the most efficient point (most Lumen per unit of current) you start getting diminishing returns the harder you push it.

Crenshaw

Q5 Emitter

350ma: 107lm
500ma: 142lm
700mA: 171lm
1000mA: 214lm

P4 7090 XRE

350ma : 80~85lm

roymail said:

DX 6090 - 600mA @ 6v for approx 80 lumens
Malkoff M60LL - 170mA @ 6v for approx 80 lumens

I know this is not scientific, but you can guess which one runs cooler and longer... with similar output.

Click to expand...

Somethings wrong with your 6090 if its only doing 80L, either that or your host is robbing it of current/voltage. it should be in the ~140L ballpark. FWIW, its the same throw distance as a Task Force, but a 2 or 3x bigger hot spot diameter and considerably brighter flood.

Just about ANY light that draws 600mA is not going to run cooler/longer than just about any ANY light that draws 170mA.

I stand corrected about the output of the 6090. Sorry, I thought the output was approx 80-100 lumens. Thanks for the correction.

The M60LL use a Q5 according to Gene's website:
"The output is 80+/- bulb lumens. The current draw is approximately 170ma at 6 volts. The runtime is approximately 8 hours, at full output, on 2 CR123 primary batteries. It will easily illuminate objects at 100+ feet. The LED is a Cree XRE 7090, Q5 bin, WG tint."

Now I'm wondering if the bin has any effect on the heat issue?

There's nothing wrong with the M60LL getting 80 lumens at 170mA. That's measured at the tailcap at 6 volts, not at the emitter itself.