A warning to all SF L4 users (please read)

Over the weekend I nearly had an incident.

I carry a cotton shoulder bag wherever I go.

Inside this shoulder bag is an internal compartment - a small zipped pocket where I keep my SF L4.

Yesterday morning while I was travelling inside a car, I felt my shoulder bag's heat increased to a level that it captured my attention.

I did not know what was going on until I opened it.

The L4 had unknowingly switched on and was scolding hot. I am not sure how long the L4 had been on. All I know was that it was very very hot.

I was trying really hard to hold it to switch it off but was unable to because of the heat. It was like a piece of red hot metal.

At this point, I was really afraid the batteries might blow

In the end I held the tail end and switched it off.

It was quite an experience.

I know now why there is a warning logo on the L4's head unit.

it was very very hot. hot like you cannot hold the L4 type of hot.

Later when I removed the battery, the thin plastic covering the battries had holes in several areas due to the heat.

My advice to all SF L4 users : if you wish to carry your L4 with you, please remove the batteries. In the event that you need to use it, insert the batteries. It is a simple procedure that will save you a lot of trouble.

The internal zipped pocked of the shoulder bag had a few cotton layers. I was still able to feel the heat generated.

You can just "lockout" the tailcap of the L4 instead of removing the batteries by unscrewing the tailcap so that the internals no longer make contact, thus effectively preventing the L4 from accidentally turning on.

Or, just lock out the LOTC.

did you lock out the tailcap?
surefire created the lock out tailcap for specifically this purpose.
to lock out the tailcap, twish anticlockwise about 1/4 or 1/2 turn,
then depress the switch to see if it lights, if it still lights, twist
anticlockwise another 1/4 to 1/2 turn.
i had this happen to me too, i had a Pr-T with 5W and it got switched
on in my bag, it was soo hot, i saw the head smoking in my bag.
now, i outfitted my clickie tailcap with a nekomane tailcap guard ring
to avoid accidental turn on and also i lock out the tailcap when
carrying in a bag.
be safe
cheers
Des

They can get quite hot in a confined space.

Why not just back the tailcap off about one half turn to lock it out. Much easier than removing batteries and ready to use quickly.

Mark

Good grief, am I the only one that considers this a serious design flaw?

I mean if this thing is getting scalding hot after a short period of time it sounds like it needs a better heatsink.

{EDIT} At the very least these powerful flashlights should have some sort of circuit that detects excessive heat and either shuts the thing off or throttles the current back.

Good morning all,

I did not know about the 'Lock out' technique in SF L4.

Thank you for this info!!!!

1 question.

When the L4 heats up, will the batteries blow?

:huh2:

I'm not sure if anyone mentioned this but you can just lock out the tailcap.

no. they are definately not designed to explode under heat.

FloggedSynapse said:

Good grief, am I the only one that considers this a serious design flaw?

I mean if this thing is getting scalding hot after a short period of time it sounds like it needs a better heatsink.

.

Click to expand...

Actually it means that is has a very good heatsink.

FredM said:

Actually it means that is has a very good heatsink.

Click to expand...

No it's not large enough. Duh.

Like I mentioned in my OP, it should have something to detect excessive temps and shut itself off before things get this bad.

Sounds like people want to carry really bright lights in small packages. The downside is they apparently cannot be left on for too long or they cook themselves. :lolsign:

FloggedSynapse said:

No it's not large enough. Duh.

:lolsign:

Click to expand...

Wow. I'm guessing you don't know what a heat sink is or what it does so I'm gonna let that pass.

FloggedSynapse said:

Good grief, am I the only one that considers this a serious design flaw?

Click to expand...

That's what the LOTC is in place for. This is not a design problem; it's operator error.

Something we tend to forget is that some of these lights are designed with very specific purposes in mind. The L4 is one of those: it's more of a tactical than utility light. Tactical lights are not typically on for long periods of time; thus the need for a heat sensing-circuit is not deemed absolutely necessary.

greenLED said:

That's what the LOTC is in place for. This is not a design problem; it's operator error.

Something we tend to forget is that some of these lights are designed with very specific purposes in mind. The L4 is one of those: it's more of a tactical than utility light. Tactical lights are not typically on for long periods of time; thus the need for a heat sensing-circuit is not deemed absolutely necessary.

Click to expand...

Well, perhaps this little 'incident' demonstrates the need for some sort of of heat sensing cutoff.

Also bear in mind that in normal use i.e. when the flashlight is being held in your hand, your body will also act as a heatsink since heat from the light will transfer to your hand and will be convected away as your blood circulates.

So in normal use, I do not expect the heat to be a serious issue. I have an L4 and I have had it turned on for several minutes at a time and while it did get hot I had no problems with holding it in my hand.

It doesent get that hot when held in the hand.
Your hand dispatches the heat away from the flashlight body...Besides the light has protection.
The LOTC...
Lock out Tail-Cap...Its there for a purpose.

I would be more concerned if the light didnt get hot..
Then there would be a major design flaw,and some serious damage to the led over time.A light getting hot is good for the light because it means the heatsink is working perfectly.






Benny

FloggedSynapse said:

Well, perhaps this little 'incident' demonstrates the need for some sort of of heat sensing cutoff.

Click to expand...

THe problem is in a confined space the heatsink wouldn't do much since there is no air to remove the heat. So in comes the lockout tail cap. And I believe they have over heat protection. But yes they have excelent Emitter-body heat transfer which makes for a much less likely cooked emitter. A large heatsink body would only help if the light was in open moving air or else the air just gets hot around the light and does not remove any heat. You need moving air not a better heatsink.

FredM said:

Wow. I'm guessing you don't know what a heat sink is or what it does so I'm gonna let that pass.

Click to expand...

More mass in the heatsink would buy you more time before the light reached plastic melting battery destroying temps. Either that, or some sort of temperature cutoff should probably be built in.

FloggedSynapse said:

I'm guessing you're just being an a$$hole, but I'll let it pass.

Click to expand...

If you feel the need to $$ out a word then its a good indication it shouldn't be used. I realise that what FredM wrote was not the most helpful way he could have explained his point.

Hint: CPF Members are welcome to report (using the built-in report function) posts or threads they consider have inappropriate content to CPF Staff for us to deal with.

However in this case my focus as a CPF Administrator is concentrated on the reaction to the comment rather than the comment itself since its disruption we're most interested in preventing...

FloggedSynapse said:

Good grief, am I the only one that considers this a serious design flaw?

Click to expand...

Perhaps you are.
These type of flashlights getting hot when activated, especially in a confined space has been normal since they were invented by SureFire like 20 years ago and copied by many hundreds of companies worldwide ever since.

FloggedSynapse said:

I mean if this thing is getting scalding hot after a short period of time it sounds like it needs a better heatsink.

Click to expand...

The flashlight body and its surface is the heatsink.
The fact that the body surface does get as hot as it does means the batteries and LED/electronics are not retaining as much heat as they otherwise would be.

FloggedSynapse said:

Well, perhaps this little 'incident' demonstrates the need for some sort of of heat sensing cutoff.

Click to expand...

There is no real need for this. In use the flashlight gets hot. Nothing to worry about since in your hand the heat is dissipated by your hand, and attached to a device (such as a firearm), you're not touching it anyway. The LockOut function is a physical measure so that flashlight does not get accidently activated when it is not in use.

The issue CPF member "Miracle" posted would appear to be the result of the L4 TailCap not being Locked Out prior to transporation. If the TailCap was correctly Locked Out then it would appear the compartment used to storage the L4 was not appropriate (it would take quite some set of circumstances for the TailCap to be rotated like 360 degrees and the push button pressure switch to be pressed sufficiently to click it on).

As for the being "really afraid the batteries might blow" - if "Miracle" was using SureFire SF123A or Duracell DL123A batteries I suggest "Miracle" should have no fear of them 'blowing'.
(I have plenty of experience using DL123A and SF123A batteries in the 12PM and M4 with the N62 lamp where the batteries became so hot they 'shutdown' and had to cool off before being used again. I normally put a set of four batteries through this thermal shutdown cycle two or three times.
I'd be interested to see photos of the batteries used but I would guess it was the wrapper shrinking rather than "melting".

I think the lesson to learn here is use the LockOut function and be mindful of the way the product is stored and transported.

Al

FloggedSynapse said:

I'm guessing you're just being an a$$hole, but I'll let it pass.

Click to expand...

That didn't help your argument any. :thumbsdow

Edit: Size15's, I didn't see that you had already addressed this in your above post.