I want to do my first mod on a maglite.
I want to use 18650 cells as I have plenty.
I have just ordered this from DX
http://dx.com/p/cree-xml-t6-5-mode-6700k-900-lumen-smooth-aluminum-drop-in-module-with-textured-reflector-58481
but what I really want to know is should I go for the 2D maglite to run it on 2 x 18650 cells or should I go for the 3D maglite to run it on 3 x 18650 cells.
Thanks
Gazo
I would prefer a 2D. The Maglite is already big and x2 form seems to balance nice in your hand.
With 2 x 18650s you'll have less cells to worry about matching voltages and using the same age of batteries (referring to amount of cycles).
Will you try a Piezo switch?
But why not a 2C Mag. (Amazon, Zbatt). Cause then you can use a convenient 18650 to 26650 battery sleeve (IOS, DX).
Confucius say... Smaller light get more use
Thanks for that, My first thoughts was a 2D but was not sure if 2 x 18650 would be enough power to drive the drop in I bought.
Might look into a 2C does it have the same size head as the 2D ??
I am new to all this what is a Piezo switch ?? any links to one of them.
I have a few different size plastic tubing here and one the 18650 cell fits into perfectly, so no problems making a battery tube up.
That is a WF-500 drop-in, so it’ll run fine on two cells.
I’m not sure about the C/D head sizes, but here is something to consider if they are the same: 4xC=200mm=3x66.67
I used a 3D because I had it, and I got 3x 18650 unprotected to fit perfectly after cutting down the spring a little. Some grinding on the front of the head (alternatively could grind the reflector I suppose).
Here’s a couple of shots.
Shows grinding, note that the only contact with the head is at the front of the reflector. I have no issues with heat however. LED was 80C after 1.5 hours on high.
Here’s how I got the cells to fit. With charged 3x18650, draw is around 1A. Never tried with two cells.
Happy Modding!
Edit: To clarify a note in the second picture, the spring is installed backwards, not the cells. Spring contacts negative end of the last cell.
pressure activates the piezo crystal that converts this pressure to an electrical signal that is amplified by electronics imbedded within the housing.
In other words... you press on the surface and an electrical charge builds up, which in turn activates the switch...
diagram from wiki
piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated, actual deflection about 2 microns)
Pros: (1) no moving parts – so extreme long lifetime since there is no wear. (2) may easily be completely sealed from the environment and thus made weatherproof. (3) easy activation by soft touch
Cons: Cost ($$) 
I don't know a good supplier. here are some to look at (Burns, Langir, Stern)
I built that same Mag mod with a 2D, (2) 18650's, PVC tubes for battery sleeves, and replaced the Mag switch with a standard reverse clicky epoxied into the old switch housing (I destroyed the old switch). Mine pulls 1.5A on high (3A to LED). Did the same grinding shown above. Not a difficult mod, but took me quite a bit of time. Oh, I also bought glass lenses from DX to replace the stock plastic one.
I also built a 3C Mag with Mag LED reflector and used a similar blank DX heatsink/reflector only used the heatsink part). Used an XP-G neutral white with Nanjg 1.4A 3 mode driver. I never did a build thread on it though.
-Garry
Thanks Guys something else to look at.
A tip a few of you modders might be interested in.
I been hunting around my workshop for bits of pipe to make the battery tube with and came across a few dense foam tubes I bought a while back from the pound store, these where in the bike section to replace the handle grips on my sons bike.
They are the perfect fit into the D maglite and a 18650 cell fits perfect inside it.
No rattle it holds everything as if it was made for it and you get 4 of these tubes per pack so enough to do 4 lights 2 or 3 D size.
Here is a few pictures.
I noticed something interesting when running a 90 minute test on my 3D Mag mod. I use packing foam around the batteries which is working great. One thing I didn’t account for was a build-up of heat within the batteries. Doing it this way basically insulates the batteries and any heat generated internally pretty much stays there. Once the batteries get run down and current draw goes up, they got pretty warm. I measured the front cell at 47C, rear one at 42C, with the flashlight head at 40C. Ambient was 17C. This is concerning, as you want to keep Li-Ions below 60C for safety and longevity reasons.
Food for thought… I’ll be looking for an alternative spacer; something that doesn’t insulate the batteries so much.
Something I did think about and will keep an eye on, I have got different size plastic tube that the 18650 fits but this fits so well I got to give it a go.
Up to now I got to be honest I have never run a powerful flashlight for longer than about 10 mins at a time, just never had the need. but something I will have in the back of my mind and can always change if need be.
Infact with the weather we are having over here it might help keep them warm, it’s 3.5c as I type this
I suppose that’s cold for the UK. Currently –10C just north of T.O. Perfect backyard ice rink weather! 
We have had it down to around –5c so far this winter but we have had non stop rain the past week or so which has turned things abit milder here.
–10c makes me cold thinking of it
Happy new year.
Indeed, Happy New Year to you too!
I'm a fan of big pictures, but please post them with size set to 100%...
Oops, sorry. I thought it was automatic. I’ll fix these and do that for the future.
Edit: Done, thanks for the tip, NightCrawl!
Just fitted the cap spring, good connection and nice and solid. Works well.
the spring alone was making a good connection but added the wire to make sure it was 100%
Did you solder that to the aluminum tail cap? Impressive...
Yes thought it was going to be a bit of a bitch to be honest, but roughed up the area got it nice and warm and it stuck a treat, I even gave it a good pull and it’s stuck well.
Wow, I've never been successful in soldering to aluminum. Of course, I haven't been particularly successful with copper either. :P
I did have a 3mm hole in the tail cap so filled that up with solder first. so guess that helped.
I then polished the outside and you would never have known it had an hole in it.
I got a 100% connection that should stay that way.