Need Help With Fatman Board & Batteries

I want to make a dimmable LuxV mod using an external potentiometer. I have been in contact with member georges80 and I am clear on how the board is hooked up, but I don't know what kind of batteries to use. At first I was thinking 4D, but it's too big and clunky.

A good choice for the Single LuxV and the fatman seems to be a single 3.6V Li-On cell, but it is very short. What could I use as a spacer to fit it into a 2C Mag...unless there is a better option.

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ooh.. there is a lot of space 'around' LiON cells in a C.... if you want the easiest mod.. i would probably wire up two 18500 cells stacked but in parallel (with wires.. and maybe a piece of two-sided pcb in between the batteries to keep pos and neg apart.. you can fit 18650s but the spring end gets complicated if you want to parallel the bats..

in any event.. you'll be able to drive a fatman to any reasonable or unreasonable level with that configuration... and get some very decent runtime...

some other nice choices: a ''mag charger' battery pack which is 5 sub-cs in the size of 3Ds.. goes into a 3D light but has 6V.. same as 4D... otherwise.. a cut-down D to 1D that has 4AAs (see fivemega).. that should work and be very small.

I think if you use a 'C' host or a 'D' host and one of b2eze's threaded heatsinks you could maybe fit a 38mm reflector for some really nice throw.

some foods for thoughts..

I'm the self-proclaimed resident expert at hacking the fatman adding such features as changing the input control from 50k to 10k.. changing the max input voltage to 13.5V so i can use 3 series Lions and a kinda neat hack for low-voltage cutout that makes the light drop from max output to 30mA when the batteries die... technical questions on the fatman.. george is awesome at answering questions.. he's the help i had to hack the fatman in ever case.. questions.. go to the source.

Oh.. another good battery choice: 3D NiMH.. i hear they have like 5000mAH.. maybe that's even just the 'c'.. 3.6V nominal down to about 3V will run the fatman great.. you can get 6+W out of 3D or 3C NiMH through the fatman even with dead batteries.

-awr

PM me if you need a spacer. /ubbthreads/images/graemlins/smile.gif

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andrewwynn said:
Oh.. another good battery choice: 3D NiMH.. i hear they have like 5000mAH.. maybe that's even just the 'c'.. 3.6V nominal down to about 3V will run the fatman great.. you can get 6+W out of 3D or 3C NiMH through the fatman even with dead batteries.
-awr

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So I could go with three 5,000 mAh C cells? I thought I could only use 4 cells!
If I did use a threaded heatsink, would there be any room for the fatman since it uses the PR base? It'd be great if I could get a threaded heatsink without the PR base or the srews so I could use my emitter.

Thank you for the offer Icarus, but I think I will be going with NiMH for this mod.

you just have to use ohms law to figure out the battery current.. as long as it's about 2A when batteries are low you are golden.

I ordered a custom threaded threaded sink from b2eze.. he hollowed out a part for the fatman.. and i just put a screw into an 'expanding nut' for the postitive power in place of the PR bulbe.. look at http://rouse.com/RT4 .. he offered to make more custom ones for $25.. totally worth it, he might be open to make more like it.

a 5W emitter probably takes close to 7W to run at full power.. divde that by 2 and you get 3.5V.. three depelted cells will be about 2.7-3V.. so.. divide 7W by 3.0V and get 2.33A.. just a little higher than the fatman will digest.. so it might dim a little bit at the end of battery if you operate at 1000mA.

to use the threaded sink you'd have to fill in the hole to use a single emitter.. there is a hole dead center.. but it's threaded so you just need some threaded rod, and i bet wilson would set you up .. you can have the emitter on a bit of a post up the center if it would help position the emitter up inside the reflector.

Oh, that sink looks nice! So, I can solder wires to the back of the fatman, right?

That PR power adapter makes contact with the back of the fatman?

the PR adapter is just stock hardware parts, and yes touches the fatman.. for the easiest for normal modding ground path return.. sand the anodizing off the top of the light body so that it will contact the heat sink.. and put a screw into the heat sink someplace and attach a ground.

The screw i found had a hex hole.. it perfectly fit a 1/8 x 1/8th cylindrical magnet, but you could use any of several solutions.. that rubber expanding nut is a 10/32 nut.. should be able to find it at a good hardware store.. or use the idea for your own solution.

wires go through the holes in the fatman and soldered from either side but the empty side is easier to solder of course.. the wires go up through a hole in the sink to the emitters.. and one to ground.. as you can see i made a sweeping ground contact because my head has to turn to operate the 3-way switch.

-awr

-awr