Is KL4 (L4) buck/boost?

I am thinking that the KL4 (L4) is buck/boost. I read it somewhere, but can not remember. I know that the KL5 is buck/ boost, as it is stated, in effect, on SF web site that three Cr123's can be used. Vital Gear recommends their FB3 for KL4.

Bill

I do think so. The buck/boost electronics boards are made for higher voltages, IIRC, and since the L4 was meant to be used with two 123s, I think it is buck/boost.

Be careful!
I do not think the KL4 is intended for use with 3x123! IIRC it is a boost-only head, thus 2x123 with the LuxV are fine and 3x123 would not be!
Just wait untill the experts chime in or you might risk your precious KL4s! /ubbthreads/images/graemlins/caution.gif
bernhard

I read many times that 2 x 4.2V R123 = 8.4V would fry the KL4.

To the best of my knowledge, the KL4 is boost as is the KL5. The KL5 can squeak by on 3x123 given the overhead of the converter and the resistance of the batteries. 3x123 is not an open invitation to 9 Vin or even 2xLi-Ion, IMHO!

The only buck/boost I am aware of in the line up is the KL1. The 5W lights are all boost with the exception of the KL6 which is a buck circuit. (Clueless on the KL7)

It stands to reason ( we won't let this stop us though) that the less efficient buck/boost drivers would not be employed in these lights which are not designed to go in a buck/boost environment.

On the other hand, perhaps one should try these heads with other battery configurations and in the event of a blown LED or circuit, certainly SF will welcome a warranty request with open arms and if not, those dirty bastids; how dare they claim world class CS! /ubbthreads/images/graemlins/nana.gif

As Bernhard suggests, perhaps some of the EE's on CPF who have visited the drivers in the SF LED lights can shed some real light or insight. In the mean time, assume at your own risk!

In fact, I considered you (Mr. Don) the expert ... /ubbthreads/images/graemlins/nana.gif
bernhard

From Surefire web site, re KL5:






The KL5 LED conversion head provides your 6P, 9P, C2, C3, G2, G2Z, M2, Z2, Z3 flashlights flashlight to high-intensity LED technology. This is no typical low-output LED system – the KL5 uses selected ultra-bright 5-watt LEDs. When powered by two 123A Lithium batteries the KL5 produces a maximum of 65 lumens of light for an hour - more than a typical four D-cell alkaline flashlight - and provides over 3 hours of total useful light. LEDs not only provide the ultimate in shock-resistance, they also provide extended runtime since they produce light more efficiently at low wattage; a battery too depleted to run an incandescent lamp can still produce usable light from an LED. The KL5 is CNC machined from aerospace-grade aluminum and coated in a military specification Type III hard-anodized finish, and features an anti-reflective coated Pyrex® window. The KL5's digital current regulation circuitry matches the LED's current requirements with battery output, maintaining a more consistent level of light output for the useable life of the batteries, unlike unregulated lights that are subject to a steady decline in light intensity beginning shortly after activation. This circuitry also protects the LED module from current and heat-related damage. Many LED flashlight manufacturers inflate the light output and usable runtimes of their LEDs, but SureFire provides realistic output and runtime specifications based on scientifically obtained measurements. Athough any LEDs can produce negligible light output for over 100 hours, the amount of useful light produced is of a shorter duration.




* Fits SureFire 6P, 9P, C2, C3, G2, G2Z, M2, Z2, Z3 flashlights
* Output/runtime - Maximum output of 65 lumens white light for one hour, followed by over 2 hours of useful light.
* Construction - CNC machined aerospace-grade aluminum with hard anodized OD finish for extreme corrosion and wear-resistance
* Pyrex® window
* Flawless beam, no dark spots or rings
* Length: 2.19" / Bezel: 1.47" / Weight: 2.8 oz.

Bill

I wonder. My L4 started life as a TW4, and apparently has a low Vf, and I've tried on 3x123 and 2 4.2V R123 without damage. Just for a matter of seconds, but if it was going to fry, it should have fried immediately. 3 new SF123s is ~9.9V.
I don't think output increased at all, either.
I've always read that it was boost only, but that sure sounds like buck/boost to me...

Bill,
Although the specs say that the KL5 will fit on the 9P,C3, and Z3, the discussion about the digital current regulation seems to follow the qualification of "powered by two 123A..". IF SF were to claim a constant current output to the KL5 from either 2x123 or 3x123, I would agree that there is an inference of a buck/boost driver. As it stands (along with my understanding) such an inference is incorrect and not really implied. I believe SF's customer base is by and large ignorant of the term buck/boost and the information provided is not to such a level of discussion. /ubbthreads/images/graemlins/icon3.gif

I've worked on a bunch of KL4s. They are indeed boost only converters. Some have gotten away with running a KL4 on 3X123, but they are just "getting way" with it. On 3X123, the LED is running in direct drive off of the batteries, less the overhead of the converter. I would imagine that your success with running on 3X123 would be largely dependent upon the Vf of your individual luxeon.

Vital Gear may be recommending their 3 cell body for the KL1, but if they are doing so for the KL4, it is a mistake.

OK, thanks guys. It is sort of confusing when SF says for use on 9P, 9Z, etc. I will be keeping my KL4, or L4, if and when I get one, at 6 volts max. Actually, it would look cute on a FB1, or E1E with R123.

Bill