Why do many use 2650 cells in D cell mag conversions?

This is an honest newbie question and I haven't done a mod with a 4 D cell mag light but I was wondering why many I've read about put something like PVC pipe in the battery tube and use a 18650 battery? It's just like it seemed a waste of space... I'm sure there is a reason - I just haven't figured it out

if you were going to use a 18650 wouldn't a C tube be less wasted space?

If using a C tube isn't a 26500 tube stronger than a 18650?

If using a D tube are there even rechargeable Li Ion D size? Are the NiMH D's as strong as the 18650's?

Isn't there a one of those huge LED's out there that can run on both D's and 18650's but if I remember right they did some butterfly looking bore on the tube where 3 18650's can fit in the same space as a D?

No offense to anyone doing mods with 18650's in D tubes - just a curious newbe!

I'm not 100% on this but most likely because D cell mags are more readily available and 18650's can be used in a more broad range of lights. If you go with 26xxx then you are limited in the lights that you can run them in. I personally have not made the leap to Li Ion's yet but I suppose I will very soon. BTW they also weigh less.

rickypanecatyl said:

but if I remember right they did some butterfly looking bore on the tube where 3 18650's can fit in the same space as a D?

Click to expand...

3 X 18650 will not fit in a D Mag, 2 will fit side by side but requires the tube to be bored.
Norm

A lot of it depends on the battery the person has on hand and can charge. Also for weight savings one might choose an 18650 over a 26650. For run times, the bigger the battery.... typically that means the bigger the so called gas tank. You can go farther with bigger cells. Bigger cells can also provide more current typically. The PVC is just a simple cheap way to hold the batteries in place and keep them safe.

This is an honest newbie question and I haven't done a mod with a 4 D cell mag light but I was wondering why many I've read about put something like PVC pipe in the battery tube and use a 18650 battery? It's just like it seemed a waste of space... I'm sure there is a reason - I just haven't figured it out

Using a 2D host gives you more options... 2x18650 or 2x26650. You just fabricate adapter tubes to match, can't do that with a C mag.
Personally I find the D mags better quality. The bezel/head assembly threads are much less sloppy fitting and the switches just feel more solid when clicked. Theres also the added heatsinking mass of the D host.

if you were going to use a 18650 wouldn't a C tube be less wasted space?
Most definitely

If using a C tube isn't a 26500 tube stronger than a 18650?
I am not sure. I have never seen any kind of strength testing done on hosts.


If using a D tube are there even rechargeable Li Ion D size?
Yes, there are 32650 Li-Io cells, ~4500AH capacity IIRC. Problem with them is that they are not IMR chemistry. Voltage sags tremendously with higher C. Youre better off going with IMR26500, IMR26650 or IMR18650. Even 3P-18650 is a better setup than a "saggy" 32650. Mrgman and bigchelis ran some tests on 32650 Li-Io cells and the results were not very impressive, for high current applications.


Are the NiMH D's as strong as the 18650's?
Most definitely. D NIMH cells hold voltage at a very high C. Problem is the size and weight. You need several of them to reach the necessary voltage required by the popular mag mods. The mass of the chemistry is also VERY heavy. So lugging around a 10 pound 4-5D mag may not appeal.

Isn't there a one of those huge LED's out there that can run on both D's and 18650's but if I remember right they did some butterfly looking bore on the tube where 3 18650's can fit in the same space as a D?
The Xtar D30 fits this description, as does the 5-Mega megallinium. Lights that have this feature are commonly called tri-bored.


No offense to anyone doing mods with 18650's in D tubes - just a curious newbe!
No problemo

I prefer IMR 26650 cells. They are easy to adapt to 32650 size with some white PVC couplings, although for lower current applications you might as well just go with 32650 Li-Io cells. If they made an IMR 32650 that would be the ideal.

18650 adapted to C-mag:


18650 adapted to D-mag:


26650 adapted to D-mag:


Its practically plug and play, being that ROP lamps work great at 8.4V.

kramer5150 said:

If using a D tube are there even rechargeable Li Ion D size?
Yes, there are 32650 Li-Io cells, ~4500AH capacity IIRC. Problem with them is that they are not IMR chemistry. Voltage sags tremendously with higher C. Youre better off going with IMR26500, IMR26650 or IMR18650. Even 3P-18650 is a better setup than a "saggy" 32650. Mrgman and bigchelis ran some tests on 32650 Li-Io cells and the results were not very impressive, for high current applications.



Isn't there a one of those huge LED's out there that can run on both D's and 18650's but if I remember right they did some butterfly looking bore on the tube where 3 18650's can fit in the same space as a D?
The Xtar D30 fits this description, as does the 5-Mega megallinium. Lights that have this feature are commonly called tri-bored.

Click to expand...

Thanks for all the great info guys! 2 follow up questions:

Do you know of anyone here who can bore a D size mag battery tube like the Xtar D30? I'm guessing there might not even be enough material... How about a any tri-bored tube that could fit a Mag D size head?

2nd question... what is IMR chemistry? I was reading about them on AW's sight and just noticed they didn't seem to be as strong (less amp hours) than non IMR... if they are not as strong why are they better?

Thanks!

kramer5150 said:

Isn't there a one of those huge LED's out there that can run on both D's and 18650's but if I remember right they did some butterfly looking bore on the tube where 3 18650's can fit in the same space as a D?
The Xtar D30 fits this description, as does the 5-Mega megallinium. Lights that have this feature are commonly called tri-bored.

Click to expand...

I was reading somewhere that the regular Mag D tube left less than 1 mm of material if one were to bore it for 3p 18650. Is this true?

The tri-bores I have seen were all 17670.... I am not sure if anyone is doing it for 3x18650

2nd question... what is IMR chemistry? I was reading about them on AW's sight and just noticed they didn't seem to be as strong (less amp hours) than non IMR... if they are not as strong why are they better?

The IMR batteries can deliver more current (much more) than the non IMR or better known as ICR. The chemistry is different. However as you already stated the amp hours are less. And I found this:
I = lithium ion
C/M/F = cobalt/manganese/iron phosphate chemistry
R = rechargeable(?)
There is a battery thread that tells you everything you ever wanted to know in the battery section, it is a sticky.

garilla said:

2nd question... what is IMR chemistry? I was reading about them on AW's sight and just noticed they didn't seem to be as strong (less amp hours) than non IMR... if they are not as strong why are they better?

The IMR batteries can deliver more current (much more) than the non IMR or better known as ICR. The chemistry is different. However as you already stated the amp hours are less. And I found this:
I = lithium ion
C/M/F = cobalt/manganese/iron phosphate chemistry
R = rechargeable(?)
There is a battery thread that tells you everything you ever wanted to know in the battery section, it is a sticky.

Click to expand...

IIRC there was a "battery university" type thread somewhere... tons of info on that thread / site.

Others can elaborate better than I the technical details of IMR versus non-IMR. In a nutshell, IMR = high C. For 18650 size cells, current draw below ~2A is fine for non IMR cells. Anything over that however and IMR cells are better.