Surefire L1 converter question

Does anyone know if the Surefire L1 uses a buck/boost converter (like the KL1), or just a boost converter?

Or, what is the highest voltage that the L1 converter can handle?



Thanks!

www.lighthound.com says that the L1 should not be used with rechargeable 123 batteries; my guess is that 3 volts is it... probably not a buck circuit but I really cannot be sure.

-Goatee

Well, I did a bunch of searching and reading of old threads... Several people have reported using rechargeables with only an brightness increase in the (unregulated) 'low' mode, but not in 'high'. To me this would suggest either a boost/buck circuit, or a high emitter Vf (probably the latter, but you never know).

Anyone want to run 6V through their L1 in the name of science ?

Also, does anyone know if protected RCR123's will fit the L1? Or just the unprotected ones?

vtunderground,

In the interest of screwing up a perfectly good flashlight, and playing "leggo" in the name of science and curiosity, I took my L1 (1st gen.) heads and screwed them onto my E1E/Z57. Very interesting results. When turned on, the RED head went to full brightness (as expected), indicating that it was receiving and thru-putting the full 3V for which it was designed. That being the case, there was no way in hell you would get away with a 6V thruput from an E2 into an unprotected L1 head (at least not for long - magic smoke, bad juju!!). So, with the RED head, I got just what I was looking for - a short version of the L1/RED on "high" and a backup platform for my RED head if my L1 regulator or tailcap went down in the field..

The interesting part was what happened when I tried the same thing with the WHITE head. I got a sickly result of about 3 (+/-) lumens!!!??? instead of the expected 15 lumens of 3V unprotected "high" output. No, I was not interested in trying 6V of unprotected thruput from the E2, so I approached it from a different angle. I decided to try the L2 (15/100 lumen) head on the E1. Nothing!! (Not unexpected). Then, I tried it on the E2 and got about 10-12 lumens of sickly output instead of an expected 60-100 lumens of 6V unprotected "high" output.

Both of the unprotected WHITE heads gave me the same result. The L1/WH gave me FAR less than normal output on "unregulated" maximum voltage. The L2/WH gave me FAR less than normal output on "unregulated" maximum voltage. WHY?? IF the L1/BL head will go to full bright on the E1 like the L1/RD does, the problem is only in the White heads. WHY?? My interest (and the reason for the experiment) was primarily in having a backup "platform" for the RED and BLUE heads if the L1 regulator or tailcap went down in the field. The WHITE output can always be duplicated by something else.

Since the "hoped-for" result with the L1/WH on the 6V E2 can be duplicated FAR BETTER with a KL-1 (gen.1-4) or KL-4 head, I saw no reason to risk my only (and favorite) L1/WH head.

Hope this helps.

The KL1 and KL4 heads have converter circuitry in the head itself. I won't try to guess whether it's boost, buck, or both. An E1L is pretty much just a KL1 head stuck on a E1 body. The E2L is a KL1 head stuck on a E2 body. The L4 is a KL4 head stuck on a E2 body.

The L1 and L2 lights are considerably different. The converter is in the body of the light, not the head. The head just has the optics/reflector, heatsink, and emitter. There are no "smarts" in the head of the L1 or the L2. The L1 has a Lux I (III?) in the head, and the L2 has a Lux V.

You probably shouldn't be swapping heads and bodies between the (L1,L2) and the (E1L,E2L,L4). If you do, you'll likely end up with a light that's in direct drive (no converter) or you have the output of one converter trying to drive the input of another. Either case is less than optimal.

The red Luxes have a relatively low forward voltage (Vf). Putting the red L1 head (which has no converter circuitry in it) onto the E1 body will direct drive the emitter. The Vf of the red lux is low enough that you get full output off a single 3 volt cell.

The white Lux I and Lux III emitters have a Vf that's typically in the 3.25 to 3.75 volt range. A single 3 volt cell does not provide enough voltage to overcome the forward drop of the Lux, and very little current flows. You will not get much light from a white Lux on a single cell. You will most likely fry it instantly if you try to drive it off an unregulated 6 volt source (two cells), but it may be very bright for that instant.

The Lux V in the L2 head has a Vf somewhere around 6 volts. If you run it without a regulator off a single cell, I'd expect you would get pretty much nothing out of it. You may get some light off two cells, but it is more likely the current draw would sag the voltage of the cells, and it won't be very bright. It is common to try to direct drive the Lux V off three lithium cells (Space Needle), but I would not recommend you try this with the L2 head because of insufficient heatsinking in the head. You also don't really know the Vf of the Lux V that Surefire used, and if it is unusually low it will draw more current than for which it is rated if you direct drive off three cells.

So, basically, there is no "problem" here. The L1 and L2 heads do not have regulation circuitry in them and they are not designed to go on E1 and E2 bodies. Red Luxes have relatively low Vf, and will go full bright off a single cell. White Luxes have a higher Vf than you can reasonably direct drive off a single cell (Lux I/III) or two cells (Lux V).

The L1 uses a BOOST converter. Maximum input is Vf of LED (plus possibly a schottky diode drop) Anything higher will direct drive the circuit.

The KL4 uses a BOOST also, same rules apply.

The KL1 uses a novel buck/boost which they achieve by tricking a conventional boost circuit on what the ground reference is Novel yes but efficiency is mediocre though.

Ty Bower,

That is what I suspected and exactly what happened! Thanks for the confirmation. The question now is - what is the Vf for the L1-BL and L1-GR heads??? Will I get the same result for them off an E1 as I did for the L1-RD??