I had a power outage back in December from an ice storm so I was tail standing a few lights to bounce light off the ceiling. I noticed that my Fenix P1 (older Luxeon ? LED) got rather warm after about 20 minutes of doing this. I'm just wondering if this heat is harmful to the LED ? This light only has one mode otherwise I would have used a lower mode. Would a newer more efficient LED give off less heat ? I may have to buy a new light if so.
Tailstanding heat
- Thread starter kaj
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Yes, this heat could be harmful to the LED. In a small light with limited heat-sinking ability (either through its mass or surface area, or both)running any LED at high current can damage the LED.
Yes, a newer, more efficient LED will produce less heat and more light at the same drive level. At a lower drive level, it could produce the same amount of light, but with much less heat and much longer runtimes.
Yes, a newer, more efficient LED will produce less heat and more light at the same drive level. At a lower drive level, it could produce the same amount of light, but with much less heat and much longer runtimes.
hoongern
Enlightened
If you want to continue using lights that you already have but get warm, one thing I do now and then is to "cup-stand" instead - place the light in a cup filled with cool water. The water helps to cool it down. But then again, this may not be a solution that you're looking for.
Sgt. LED
Flashaholic
I've done the cup stand as well with hot running lights and as long as it's not cold cold water in the cup it does just fine.
bladerunner
Newly Enlightened
Interesting question. Last night I ran my Fenix L1D for maybe 20 min. tailstanding. It was quite warm when I shut it down. How much can it take? I don't know. How many run time tests have been done on this forum and no damage afterward? How many got damaged? I guess anything you can do to aid in the heat dissipation is good. I kind of think that an expensive light would have some engineering expertise built in to protect it. Just my 2 cents...and random thoughts.
march.brown
Flashlight Enthusiast
Surely on a single mode light from a well known maker , the torch should be capable of running continuously ... They can't sell you a light and then say that it cannot be run for long periods ... You should write to them and explain that you are worried about the heat ... Part of the design of an everyday torch is that it can be used as much as you require.
I realise that some people use higher voltage batteries in their torches and in that case it is to be expected that the torch will overheat , but surely not in an everyday torch !
Perhaps they will tell you that the torch body needs to be in contact with the human hand to act as a heatsink and that therefore the torch is not intended to be used for tail-standing.
When I tested my Solarforce L2s (on high) for run-time , they got warm but even after 90 minutes were well within limits and they were just leaning against a book ... After 90 minutes the 18650 batteries still had 40% left in them which would be another hour of use ... I would have no problem using these torches for over two hours continuously on high ... To me , that is exactly what you should be able to do with the everyday torch of your choice.
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AnAppleSnail
Flashlight Enthusiast
Part of the design of the flashlight is that they are normally used in the hand. Most makers DO advise you to be careful tailstanding the light. The main mechanism of cooling the light body is conduction into your blood supply. Building lights that could be aircooled in all conditions would require comically large lights at low power levels. Maybe his house is warmer than yours.
DM51
Flashaholic
The demand for ever-smaller and ever-brighter lights has risen continually, and the makers do their best to meet it. This gives rise to heat problems when the light is left standing on its own.
The human hand is in fact a good heat-sink, and many lights are designed around the fact that the hand holding the light will help conduct excess heat away. When the hand is not there, air has to do this job, and air is much less efficient at conducting heat.
So: small lights left tail-standing can over-heat. Is this a problem with your light? There's an easy test:
1. If you can pick it up and hold it without discomfort, it is OK - it hasn't overheated.
2. If it is too uncomfortable to hold, it is in danger of overheating, so you should turn it off and let it cool.
3. If you pick it up and 1/2 sec. later yell "YEOOOW!!" and drop it, you have a more serious problem.
Overheating will in most cases damage the batteries before damaging the light itself. Bear in mind that over-heated batteries can be dangerous.
The human hand is in fact a good heat-sink, and many lights are designed around the fact that the hand holding the light will help conduct excess heat away. When the hand is not there, air has to do this job, and air is much less efficient at conducting heat.
So: small lights left tail-standing can over-heat. Is this a problem with your light? There's an easy test:
1. If you can pick it up and hold it without discomfort, it is OK - it hasn't overheated.
2. If it is too uncomfortable to hold, it is in danger of overheating, so you should turn it off and let it cool.
3. If you pick it up and 1/2 sec. later yell "YEOOOW!!" and drop it, you have a more serious problem.
Overheating will in most cases damage the batteries before damaging the light itself. Bear in mind that over-heated batteries can be dangerous.
march.brown
Flashlight Enthusiast
I guess the answer is "Don't tailstand your torch"
Maybe that is why some torches , like the iTP A series , won't tailstand.
I assume that the torches that come with a headband are too low in power to overheat ... That would limit cavers and potholers to low power torches though ... There again , it is "black dark" in the vast majority of caves so maybe a high power torch might not be needed ... A torch that runs hot is quite useful to warm your hands on in a cold damp cave.
I don't like the idea of standing a torch in a mug of water either , when there obviously are torches out there that will tailstand with no problem ... I have two Solarforce L2s that won't tailstand , but will lean against a book (or similar) and won't overheat even on full power for 90 minutes ... I have a Solarforce L2i converted to 18650 that will tailstand and again it will run OK for 90 minutes on full power ... My Dropins on the L2 are three mode and on the L2i a single mode ... The three modes are great as there is the choice of low , medium and high power ... I don't know how long the low and medium modes will give but the high will give me two and a half hours continuous running.
The only reason that I know these times is that I tested my three Solarforces on high , propped up against a book just to see how long the battery would last ... At 90 minutes , the voltage on the 18650s was only down to 3.8 volts , so there was still an hour left.
If I ever needed to tailstand a torch , I know that my Solarforces are suitable.
As a matter of interest , which metals are the best for conducting heat away from the dropin ? ... This assumes that the dropin is in good thermal contact with the body of the torch ... I've always assumed that aluminium was the best.
.
Maybe that is why some torches , like the iTP A series , won't tailstand.
I assume that the torches that come with a headband are too low in power to overheat ... That would limit cavers and potholers to low power torches though ... There again , it is "black dark" in the vast majority of caves so maybe a high power torch might not be needed ... A torch that runs hot is quite useful to warm your hands on in a cold damp cave.
I don't like the idea of standing a torch in a mug of water either , when there obviously are torches out there that will tailstand with no problem ... I have two Solarforce L2s that won't tailstand , but will lean against a book (or similar) and won't overheat even on full power for 90 minutes ... I have a Solarforce L2i converted to 18650 that will tailstand and again it will run OK for 90 minutes on full power ... My Dropins on the L2 are three mode and on the L2i a single mode ... The three modes are great as there is the choice of low , medium and high power ... I don't know how long the low and medium modes will give but the high will give me two and a half hours continuous running.
The only reason that I know these times is that I tested my three Solarforces on high , propped up against a book just to see how long the battery would last ... At 90 minutes , the voltage on the 18650s was only down to 3.8 volts , so there was still an hour left.
If I ever needed to tailstand a torch , I know that my Solarforces are suitable.
As a matter of interest , which metals are the best for conducting heat away from the dropin ? ... This assumes that the dropin is in good thermal contact with the body of the torch ... I've always assumed that aluminium was the best.
.
Whatever light I'm using if I'm going to tailstand it for awhile I just don't put the light in it's highest mode not only for heat but for battery life. For multi mode light's that get hot on the max mode the next mode down is usually sufficient especially if your in total darkness.
HKJ
Flashaholic
This is some very good rules for aluminum flashlights, but stainless steel and titanium lights might overhead, even if you can hold them, but this depends on the actual design.
A led can usual take up to 150 °C inside, from the inside to the mounting base their might be 30 °C. This means that a flashlight can be rather hot around the led!
GregWormald
Enlightened
Warm? Too warm?
Most solid state stuff is good to about 60°C, so as long as the LED and the associated electronics don't exceed that for any length of time you should be OK.
Basically, what DM51 said.
Greg
Most solid state stuff is good to about 60°C, so as long as the LED and the associated electronics don't exceed that for any length of time you should be OK.
Basically, what DM51 said.
Greg
bladerunner
Newly Enlightened
50 C is 122 F. 60 C is 140 F. Both would feel quite warm..hard to tell by hand where it really is. The hot water in your kitchen sink is around 120 F if you have a modern/up to date hot water heater. They are limited to pervent scalding. So 140 F should hurt.
HKJ
Flashaholic
That is not really correct, most power chips goes to 120 - 150 °C inside, non power components are at least 70 °C.
And as I wrote before a led is typical 150 °C, here is a link to XP-G, look for "led junction temperature".
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