L1 has its age, presented in 2005 was for a long time the unsurpassed example of headlamp powered with 4 AA-size batteries. Refined driver provides a constant amount of light for approximately 80% of the capacity of cells and then switches to economy mode. Possibility of attaching the container of the D-size cells allows to extended more than twice the working time of the lamp.
At the beginning it should be noticed that the same headlamp can be purchased under two brands names Silva L1 or Brunton L3.
Some marketing data :
Output: 3W (3-Watt Luxeon LED)
200 hours battery life
Light distance to 207ft
Four light modes for high output or conservative use
Emergency flash mode
Includes external battery pack (holds four C batteries)
Costs : 100$ for Silva an 85$ for Brunton.
The offer looks quite impressive, beside runtime that is always counted to the last photon coming from the led. Headlamp is water resistant only so I wouldn't advise swimming in it...
I get In my hands version powered from 4xC pack, using common available NiMH’s you can get 4Ah battery pack instead 2,5Ah from AA size cells. The only issue is that the 4xC pack is four times bigger than 4xAA holder - but long cable and clip allows carrying it on the belt or in the backpack.
The first thing for a flashaholic is nicely designed heatsink composed into the head. At last one designer have read led specification to the “Thermal management” chapter.
Opening the head isn't a special problem, you have to leverage with the knife head parts along joint, to crack glue and then it will split into 2 parts. Inside there is standard optics in holder (fi 20mm), emitter is mounted on the thru-hole pcb that allows connection between the slug and the heatsink. At first look it looks like a piece of cake for a modder.
Sorry folks it won't be so easy, after desoldering emitter from the pcb the problem starts – it is impossible to remove emitter from the heatsink. After some needle scratching you will find solid glue all around emitter. I removed emitter using small chisel and hammer . After that you have to clean up heatsink from the rest of the glue and solder a new led.
Under the head strap you will find some nasty label "Warranty void if seal is broken” after removing it and unscrewing back cover you will se some wires and two quite big electrolytic capacitors (47 µF 16V) - in general nothing interesting :-D.
After removing the cover with the „Silva L1” logo you can get to the driver . On the one side epoxied unknown chip, but on the other side familiar looking chip.
Based on the markings recognized as Sipex SP6651 - buck type driver.
Below, you can see comparison of the led current and the voltage drop from the power source (I get some crappy and used batteries with the headlamp 5,23V without load )
Luxeon SSC P4 USX0H V-in
LOW 2,625V 27 mA 2,625V 43mA 4,83V
MID 2,824V 130 mA 2,810V 154mA 4,09V
HIGH 3,083V 230 mA 3,025V 266mA 3,28V
It can be seen, how Fast source voltage drops, unfortunately I checked that after replacing the led so below comparison shots are for above mentioned currents.
After changing power source to freshly charged AA NiMH’s (5,54V without load) there is a major current change.
V-in I-In P-In V-led I-led P-led Eff.
5,50V 47 mA 0,26 W 2,64V 56 mA 0,15 W 57,19%
5,14V 231 mA 1,19 W 2,89V 270 mA 0,78 W 65,72%
4,93V 580 mA 2,86 W 3,25V 683 mA 2,22 W 77,63%
On a bit used AA NiMH’s the situation is very similar (5,24V without load).
V-in I-In P-In V-led I-led P-led Eff.
5,13V 54 mA 0,28 W 2,62V 54 mA 0,14 W 51,07%
4,71V 262 mA 1,23 W 2,85V 260 mA 0,74 W 60,05%
3,89V 663 mA 2,58 W 3,22V 657 mA 2,12 W 82,03%
Comparison shots between Petzl New Myo Belt XP ’08 (based on SSC P4 and powered from 3 new AA alkalines) and modded Silva L1 (powered from 4x slightly used NiMH’s AA)
After modd you can get very strong headlamp - there is an accumulation between voltage driving and low Vf of the led. On 3,2 volt the led is sucking from the driver over 650mA !
Powering the headlamp from 4 cells instead of 3 with a connection with nicely designed driver and led heatsink allows us to be happy from almost same powerful headlamp as the New Myo XP in the boost mode for a few hours not only for a moment.
Narrower optics improves effect of the high light output – for some people it can be disadvantage, for other advantage – i.e. the Myo have diffuser lens, for Silva you have to buy them separately (there is white or red available).
But if you have Silva L1 / Burton L3 headlamp, some skills and desire you can give it new life (led ) for a next few years of duty.