Fenix Turbo Mode

I have only one Fenix flashlight, and this is the L2D Cree Q5. It is stated in the user's manual that the Turbo Mode should not be used for more than 10 minutes continously as this may harm the flashlight due to heat build up. How about the P1D, P2D and the P3D, do we also have to limit the use of Turbo Mode to less than 10 minutes? Thank you.

It's not a hard limit, just a guideline IF you are using it in a manner which allows excessive heat buildup. If you keep your hand on it, you help take away heat. General rule of thumb is as long as you can comfortably hold the light in your bare hand, you should be fine.

That limit is to prevent overheating the light and also apply to the other Fenix lights.
BUT it only apply under very hot conditions or when no cooling is applied to the flashlight. Cooling can be airflow or a hand holding the light.
I.e. as long as your can hold the light in your hand, your can use turbo mode.

I am using the L2D in turbo on my bicycle, it does not get hot when used for 30 minutes, because it has air cooling.

Hi edap617,

I don't think you need to take that warning as a hard and fast rule. If you are holding the light you will stop it getting too warm by conducting heat away in your blood, I use mine like that and haven't ever had a problem. If you are leaving the torch then it would be best to turn it down a bit. Again, use your common sense and check it occasionally.

The 'high' level is not much dimmer than 'turbo' and keeps it considerably cooler as well as being kinder to the cells, you may find that it is a better mode to keep it on when you intend to leave it on for a prolonged period.

Andrew

It's mainly for high ambient temperatures or when the light is on buy itself with no way of preventing the heat from building up.

So when you use the light in your hand, it should have no problem running in turbo.

I frequently ran mine on turbo for 2 hours on a bike. As others say if it doesn't get too hot then it is fine.

Marduke said:

If you keep your hand on it, you help take away heat.

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Btw. everyone says that, but has anyone verified it?

My friend did and he found out that in both cases the temperature settled on the same value (43°C (109°F)). Room temperature was 23°C (73°F) and measurement was done with infrared thermometer. And I think that 43°C is pretty safe temperature and no one has to worry about any damage.

jirik_cz said:

Btw. everyone says that, but has anyone verified it?

My friend did and he found out that in both cases the temperature settled on the same value (43°C (109°F)). Room temperature was 23°C (73°F) and measurement was done with infrared thermometer. And I think that 43°C is pretty safe temperature and no one has to worry about any damage.

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People in the past have verified it, and it is simple thermodynamics. Blood absorbs heat much more readily than air.


It also depends on the light. Larger lights will have a smaller (if any) window of difference. Small lights which heat up quickly will show a vastly different temp between both cases.

there have been two threads on fenix turbo mode recently....

Crenshaw

I agree that there may be some difference with small lights or in very high ambient temperatures, but there is no difference with L2D Q5 in turbo mode.

jirik_cz said:

I agree that there may be some difference with small lights or in very high ambient temperatures, but there is no difference with L2D Q5 in turbo mode.

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On what battery?? Left unattended for an hour or so using NiMH or L91's, it will get too hot to comfortably touch for more than a few seconds. If yours does not, you have a uniquely superior sample.

Alkalines can't sustain high enough power for it to get very hot in turbo.

jirik_cz said:

I agree that there may be some difference with small lights or in very high ambient temperatures, but there is no difference with L2D Q5 in turbo mode.

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The question is, how long did the test last?
Taking measurements for the first 5 minutes will tell you nothing about the temperatue after 15-20 minutes. Holding the light in your hand will help getting heat away, but ONLY if the light is warmer than you.
It's like those liquid-cooled Computers. The effect will be even better, when the difference in temperature of the flashlight and you will be higher.
Just Thermodynamics ( 3. main clause of thermodynamics to be precise)


Just for thinking: What will freeze first when put into the freezer?
1. A cup full of hand-warm water,
or
2. A cup full of boiling water?


MfG Mr.Urahara

Ok, here is the graph. He used ni-mh batteries. Green is Fenix "cooled" by a hand and violet is light without cooling.

Can anyone point me on some tests in the past? I can't find any...

Marduke said:

Left unattended for an hour or so using NiMH or L91's, it will get too hot to comfortably touch for more than a few seconds.

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How much degrees means "too hot to comfortably touch"? Temperature higher than your body temperature always seems "hot".

Whenever optics HQ gets their surefire C2 HA's in stock and sends me mine I'll get you some hard numbers using a non-contact thermometer. The surefire L4 would be great for this test but I don't have one anymore. From checking other aluminum surfaces(power amplifier heat sink, etc) I've found that the "too hot to hold comfortably" mark is around 120-140 F or 50C

I would have to agree. Around 50C, things get uncomfortable.

do you have more data, or does the temperature settle at this point?
From the graph it seems to still increase after 30 minutes.


43C° is a save temperature.
Can you please provide the Model of the infrared Thermometer?






And for all thinking about the cups full of water, the on with the boiling water will freeze first, the other one will take far longer...


MfG Mr.Urahara

jirik_cz said:

Ok, here is the graph. He used ni-mh batteries. Green is Fenix "cooled" by a hand and violet is light without cooling.

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The graph shows the one being held in hand warms up more quickly since the hand is bringing the light up to 98.6F, body temp. Then the light continues to warm.

Were the measurements being taken at the same spot on each light? Was the spot being measured covered by the hand? Or was the hand holding the body of the light, and the measurement was being taken from the head? A test of 31 minutes doesn't appear to be long enough. A test of 60 minutes would be more telling. If this was with a L2D being tested, the results aren't very surprising. You should try this test with something like a P2D on Turbo.

I don't know the exact model of the thermometer, I have only this image


He did test without cooling first. The temperature didn't change in time from 27 to 30 minutes, so he stopped measurement at this point. From the graph it looks like temperature in hand may rise, but I think that only a little. He also said, that it was pretty boring to sit in the lab hold the light in a hand and measure the temperature every minute

jirik_cz said:

I don't know the exact model of the thermometer, I have only this image

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The measurement are probably not very accurate, these kind of IR thermometers are measuring the average temperature of a rather big circle. Your might be able to read the size of the circle on the meter (look at the side, it looks like that), beware that it is depend of the distance to the target.

Your temperature might be 50% light and 50% wall, or any other ration, depending the circle size.

Another problem is that the temperature reading will depend on what surface your are reading it from.

WadeF said:

Were the measurements being taken at the same spot on each light?

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Yes.

WadeF said:

Was the spot being measured covered by the hand?

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No.

WadeF said:

Or was the hand holding the body of the light, and the measurement was being taken from the head?

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Yes.

WadeF said:

A test of 31 minutes doesn't appear to be long enough. A test of 60 minutes would be more telling. If this was with a L2D being tested, the results aren't very surprising. You should try this test with something like a P2D on Turbo.

Click to expand...

It is your turn now

HKJ said:

Your temperature might be 50% light and 50% wall, or any other ration, depending the circle size.

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Circle size was less than head diameter.

HKJ said:

Another problem is that the temperature reading will depend on what surface your are reading it from.

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Yes, but that would add the same error to both measurements.