emergency runtime

I`m looking for something resistive to drop in the bottom of my FENIX P1.

To increase runtime in an emergency.

any suggestions.

As in modding the P1 for greater runtime?

Bring spare batts

Well, even though I too have wanted a simple drop-in current limiter, I don't think I would try this, since it is asking for trouble. I hesitate even to post this because I imagine it will draw criticism as a bad idea and might lead to someone shorting a battery, but it would be cool if someone could manufacture something reliable based upon this simple idea and offer it for sale one day.

One might be able to use a very small 20-50 Ohm (maybe more depending on needed lumens and run time) resistor with the leads clipped and bent to form a slightly twisted "U". Then, a thin metal disk could be soldered to each lead to form parallel plates. An insulating layer of thin rubber sheet, vinyl, or silicon rubber could be glued or applied to the bottom of the disk that will contact the battery so as to prevent the disks from touching one another. The edges of these battery contact disks would also need to be insulated (silicone rubber?) to prevent shorting to the battery tube and bypassing the resistor; or worse, shorting the battery terminals. The resistor should be as small as possible (about 0.126"x0.075" is one of the smallest sizes if I recall) and be able to dissipate at least 1/4W. A dab of silicone rubber could insulate the resistor leads close to the resistor body, which would probably have to be located against the very edge to clear the battery. Notches in the plates would provide more space for the resistor. A variation using a surface mount resistor might also be possible.

Additional disclaimer: I do not know if this could be made to be reliable by a DIYer and I do not recommend it.

Essentially the same idea was presented about two years ago from the Arc LS enthusiasts. It might be difficult to find the related threads, since the search engine doesn't like to search any thread that doesn't have a "recent" post in it somewhere. Maybe one of the old timers can dig up one of the old threads?

Anyway, the idea actually works relatively well. I think double sided foam tape was used as the "core" of the drop-in.

Double sided foam tape. That's a great idea! I would like to see that thread.

Mudman, why make the assembly more complicated than you need to? Take a disc of double-sided printed circuit material (diameter dependent on battery size used), etch a narrow band off the perimiter of both sides (to avoid shorting to battery tube), cut a narrow notch about 1/8" deep in from one edge (width depends on dimensions of your surface-mount resistor), tin the copper on both sides (to minimize resistance due to corrosion), and mount the surface-mount resistor in the notch (one end soldered to the copper on each side).

You get your 2 metal discs securely attached to an insulating spacer in a pre-made package 1/16" thick.

It sounds like rwolff and mudman_cj are describing a fixed resistance drop-in module. The object I remember was actually offered a two stage switch function. You tighten the twisty slightly, and the resistor makes contact with the cell and the body, and you get low mode. Tighten it up a little father, and you compress the foam tape and short out the resistor. Voila, you now have high mode.

I think you sorta wind the legs of the resistor around into the shape of a short spring. Naturally, resistor leads don't have much spring in them, so slide the foam tape in between the turns of the spring. You really only want about one turn in this spring. Now drop the whole assembly into the end of your light.

I really wish I could find the old threads.... The pictures speak a thousand words.

edit... Here it is!
http://candlepowerforums.com/vb/showthread.php?t=39298

wasn't this mod made up for the Fire~Fly? Check the Sandwich Shop....I seem to remember that the unsold mods were put in the Sandwich Shop. But then again....my short term memory has taken a beating lately!