Fenix L2P hi-low Mod does it work?

Does the Fenix L1P resistor 2 stage tail cap mod work with the L2P? I've seen it hinted at in other threads but seen no definate answer. I've modded three L1Ps and been impressed. My questions are does the resistor affect the regulation circuit in the "2" and what sort of run time has anyone achieved using what resistor.

AFAIK, the 2-stage mod is not recommended on the Fenix L2.

Does anyone know why? Is it because of the regulation circuit? Fenix probebly don't recommend that we mod the L1p but we've al done that with no problems

Yup, it's the regulation circuit. A current-regulated light will draw increasing current as voltage goes down in order to maintain regulation. Adding a resistor will make the circuit and batteries work harder, leading to a not-so-good efficiency.

It SHOULD work as long as you drop it down enough to drop out of regulation.

wwglen

Yes, it will dim the light,

but its not recommended,
it makes the L2P circuit try to draw more current,
and makes the light run hotter.

~John

Thanks all - you've save me from wreaking a Fenix!

I designed a custom 3 watt circuit for the Fenix L2P for the CPF member Erasmus that will work fine with the resistor mod (He hasn't got it yet, his circuits are shipping next week). The current draw starts at 1.5 Amps from the cells and is limited to 1.6 Amps. Alkalines won't work real well with this mod because they would have to put out 1.6 amps of current.

Will using a 4.7ohm resistor drop it out of regulation?

10 ohms works great with the stock circuit, so 4.7 ohms will just make it brighter. I read that the stock driver will still put out light with up to a 50 ohm resistor, but of course it's about un-usably dim at that point.

Ok Eric, will the 4.7 resistor harm the circuit or emitter in the L2P head? I'm using it with L1P body and single Nimh AA.

lightningbug said:

Ok Eric, will the 4.7 resistor harm the circuit or emitter in the L2P head? I'm using it with L1P body and single Nimh AA.

Click to expand...

Not at all.

jtice said:

Yes, it will dim the light,

but its not recommended,
it makes the L2P circuit try to draw more current,
and makes the light run hotter.

~John

Click to expand...

Wrong, you can't draw more current through a resistor with the same voltage available. You are actually droping the regulator out of regulation. No harm will ever come to the switcher in this senerio. Once you find the resistor that gives you the desired brightness, the resistor will simple limit the current that gets to the driver.

Now, I don't recommend this mod for the L2P head on an L2P body, only for the simple reason that the efficiency drops by a lot because of the power being disipated by the resistor. The mod using the L2P head with an L1P body however is perfectly fine.