# Streamlight Argo HP --> 18650 possible?



## yellow (Dec 12, 2006)

Just recently I jumped onto the 18650-train.
As I still need a good headlamp (mod) I think about modding an Argo HP, but am not sure if the batt compartment could be bored to the 18,2 mm diameter needed.
Anyone who has an Argo, could You please measure the lamp and give some info?

Or are there any other headlamps using 2 pieces of CR123 batteries?


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## Windscale (Dec 12, 2006)

Or are there any other headlamps using 2 pieces of CR123 batteries?[/QUOTE]

Try the Favourlight 3 Watt (reviewed in flashlightsreview.com).


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## yellow (Dec 12, 2006)

but the batts are not in line there
(I checked the 3 lights with this batt type mentionned in flashlightreviews)


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## Pumaman (Dec 12, 2006)

no way 18650 can fit


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## yellow (Dec 13, 2006)

well why?
if You posted "the batt compartment has a diameter of xx and thus cant be bored to the 18 mm needed" would have been much more helpful.

Anyone please measure the outer diameter of the batt compartment?


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## nzbazza (Dec 13, 2006)

Use a 17670 Li-Ion rechargeable. It fits perfectly. Search the forum for a recent thread w/ pix.


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## EvilLithiumMan (Dec 13, 2006)

Ha-Ha! (on me) - My first response was going to be: "Look, I've got an HP. I've got a 18650 cell. It just won't go. Not enough material for boring. Trust me." But at yellow's insistance for a more technical answer, I'm starting to think it just might be possible. I still think it's a tough call - you'd have to remove the contact strip support guides plus a little more material from the tube. And you would have to rely on the 18650 to hold the contact strips in place. IE - if you pulled out the 18650 cell to charge it, the contact strips would fall out. Perhaps they could be glued into position. I'm not sure I've got the tools or skills to make it happen. But with an approaching long holiday weekend and a couple of beers, I just may put my HP "under-the-knife".


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## yellow (Dec 13, 2006)

wow, great photos
awaiting Your findings (and looking on where to get an Argo HP)

I hoped that there might already be some "rattle" with the CR123s + enough material for widening the diameter + the leads be possible to change accordingly (both into the end caps) ...
and it looks like it will be possible.


PS: not willing to use 17xxxs. In my opinion they are completely useless. Not much better than the 14xxx models, but almost the size of the (much better) 18650...


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## Pumaman (Dec 13, 2006)




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## Doug S (Dec 13, 2006)

EvilLithiumMan said:


> Ha-Ha! (on me) - My first response was going to be: "Look, I've got an HP. I've got a 18650 cell. It just won't go. Not enough material for boring. Trust me." But at yellow's insistance for a more technical answer, I'm starting to think it just might be possible. I still think it's a tough call - you'd have to remove the contact strip support guides plus a little more material from the tube. And you would have to rely on the 18650 to hold the contact strips in place. IE - if you pulled out the 18650 cell to charge it, the contact strips would fall out. Perhaps they could be glued into position. I'm not sure I've got the tools or skills to make it happen. But with an approaching long holiday weekend and a couple of beers, I just may put my HP "under-the-knife".



Very nice photos! The second one has me a bit confused though. The labeling makes it look as if the positive and negative contacts are shorted together.


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## EvilLithiumMan (Dec 13, 2006)

Doug S said:


> Very nice photos! The second one has me a bit confused though. The labeling makes it look as if the positive and negative contacts are shorted together.



There is about a 2mm gap between the contacts. It's a little hard to see because of the angle of the camera, but it is the "bright arc" in the photo.

The heck with long weekends and beer, I've started the mod. I'm about 2/3 done and about 90% confident the 18650 cell will fit. (Although now that I'm this far along, I'm wondering if the 3.7V Li-Ion will even drive the 6V Argo to full brightness?) It hasn't all been a bed of roses. Ugly details and pics to be posted in a few hours, I hope.


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## Bullzeyebill (Dec 13, 2006)

A 17650, 17670, or 18650 will run in the Argo HP though output will proably be somewhat reduced. I do not think that the HP circuit is set up for buck/boost, and no doubt is a buck circuit.

Bill


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## Doug S (Dec 13, 2006)

Bullzeyebill said:


> A 17650, 17670, or 18650 will run in the Argo HP though output will proably be somewhat reduced. I do not think that the HP circuit is set up for buck/boost, and no doubt is a buck circuit.
> 
> Bill


Actually, if it is a reasonably designed stepdown switcher (buck), it likely will be about the same brightness as with the stock 2xCR123. For typical Luxeon Vf, a single Li-ion is nearly fully discharged before the buck would have to stop switching and go into direct drive mode.


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## EvilLithiumMan (Dec 13, 2006)

Because my posts are always long winded, I'll start with the conclusion:

Good news - the Argo HP can be modded to accept a 18650 Li-Ion cell and still run it at full brighness.

Bad news - the mod is pretty much irreversible. I don't see CR123 cells going back in after all the material that has been removed. (Although one might be able make a spacer to enlarge the 16mm CR123 cells diameter to 18mm)

Long winded part:

Start by completely disassembling the Argo HP. The positve battery cap is a snap fit, not threaded. It's on pretty tight, but using a pair of padded jaw pliers with a "twist and pull" motion will remove it without damage. Remove the bezel, lens and two screws that secure the LED module. The module is also a little bit of a tight fit. Just use a small bladed screwdriver and carefully work it out along the circumference, "coaxing" it to the front.

Now the ugly part. I was hoping the battery contacts would easily slide out of their retaining rails, but no such luck. The contacts have a pair of "teeth" on them that pretty much ensures once they are installed, they stay that way. Another problem is that the contacts aren't very thick, so they became a little bent up during removal. I had to reshape them and grind down the rough spots. If anyone discovers a neater way to remove them, please share.

Once you are down to the shell of the body, you can start boring it out. It took me about 90 minutes of filing with a rat ******* file to remove enough material for the 18650 cell to fit. (It may not have been a rat ******* file, but I like to say "rat *******") (place rim shot here) (OK - I stole that line from another post, but you still laughed, right?)

Because there are no longer any guides to hold the battery contacts, you have to rely on the 18650 cell to keep them in place. So you want the final fit to be snug. (But not so snug the positve contact cuts through the cell's insulation. Talk about a disaster! Wish I had a protected cell for this project, but I don't). If I end up with a short, I'll be kissing my Argo goodbye.

When assembling the light, start by placing the positive contact on the cell and installing from the positve side. Install the positive end cap. Now carefully slide in the negative contact strip. Be sure leave a little bit of the negative contact strip sticking out beyond the threads so it makes contact with the battery cap. Before installing the PCB/LED module, measure the 
voltage on the contacts, verifying 3.7V is present.

As far as charging goes, I'm leaving the cell installed and using alligator clips. I don't think it's worth the risk of monkeying around with removing and reseating the contacts to do a charge.

Here's some pics:


















ELM


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## Doug S (Dec 13, 2006)

Nice work. Since you have had a chance to examine the construction of this light, you can answer a question I have wondered about. How would you rate the watertightness of this headlamp? 
If you had it to do over again, would you do the same or settle for using the lesser capacity 17670 cells?


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## cy (Dec 13, 2006)

posted a thread modding argo hp with Sbin and 17670 awhile back. 
excellent little light! used it for several extended run jobs underneath a truck. ran for 5-6 hours, still had plenty of juice left.

http://candlepowerforums.com/vb/showthread.php?t=134811


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## EvilLithiumMan (Dec 14, 2006)

Doug S said:


> Nice work. Since you have had a chance to examine the construction of this light, you can answer a question I have wondered about. How would you rate the watertightness of this headlamp?
> If you had it to do over again, would you do the same or settle for using the lesser capacity 17670 cells?








The Argo HP is rated as being "water-resistant", not "waterproof", so you really shouldn't dunk it in a sink full of water. Of course, you shouldn't really try to stuff a 18650 cell into it either.

My Argo failed the dunk test - a small amount of water entered the positive cap end, despite there being an o-ring. But I'm pretty sure I have compromised it's seal by having it off a dozen times during this mod. First time I removed it, it took a healthy "twist-and-pull" to get it off. Now it's a lot easier to remove and even has some play to it when installed. The bezel and negative (threaded) cap were completely dry. 

Would I do the mod again? Certainly. It's the challenge. It's the knowledge that I now have as much Li-Ion capacity (2400maH) as is practical. Did I risk ruining the Argo HP? Certainly. But when you rip into a flashlight like a chimp into a cupcake, that's the risk you take.


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## Doug S (Dec 14, 2006)

Thanks!


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## Pumaman (Dec 14, 2006)

my hat is off to you ELM!!!!
now eating my words


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## yellow (Jan 5, 2007)

*got the HP just a day ago*

... boy, this light is SMALL!
I thought I got a wrong one when I opened the envelope (till now, 2 pcs. Cr123A was the size of a SF 6P to me ...)
be4 starting with getting the interior out, I wasnt even sure if the other driver might fit in ....

After removing these contact plates, my 18650 got into the body till to the "reels" mentionned. When they are removed, no problem. And I think there is still some material left to widen a bit and put the contact plates (with a little cutdown) back in. Just have to be epoxied, but ...
Much better than my 1st idea of outside wires.
When it comes to emitter and circuit, there really is enough space for a realistic heatsink, board, on/off/level switches in front of the emitter (light will be switched by turning the head). 
The now not needed hole for the original switch will hold an extending rod of aluminium, mounted to the heatsink inside, to get some heat away.

If ever finished, what a small, but powerful light, able to run for the full battery power without overheating


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## mdocod (Jan 8, 2007)

something to consider..

some lights that use those 3xAAA configurations in the lousy little battery cartrages.. can be modded to accept 18650s also... not sure if any headlamps like this have the internal length.. but I have some 3xAAA hand held lights that can fit 18650s with the springs removed and slight mods done to tail caps...


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## yellow_at (Jan 18, 2007)

just if someone was interrested:
I have now widened the interior enough to epoxy the contact plates there, and the 18650 going in and out with almost no force needed (depends on position of the feedback wire inside the cell)
So no ouside marks for this mod.
Quite a work, as I had to do this by hand and sandpaper.
Of course 2 CR123 still fit in, but would rattle without some kind of tube.

Only weird thing I notice is, that the cap seems to "eat" into the treads. No matter how easy one closes the batt compartment, when reopening it, there is some force needed. This has already been so in the original state.
:thinking: 

PS, just if someone wonders: my compi got infested with some unwanted programs and, till now, I was not able to log on with my original cpf account.


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## mdocod (Feb 2, 2007)

i just ordered one of these headlamps... pretty much planning on using 17670s in it so the cells can be reliably changed out as needed. (ordered it for a caving trip i have planned at the end of the month. I figure the long runtime and regulated output would be good for this use, not to mention, I have plenty of 17670s around here already.)... but If I can figure up a reliable way to make 18650s fit, and be changed out easily, I might consider it... but every light I have taken the "rat *******" to has usually never been the same since (durability and reliability wise).


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## yellow (Mar 9, 2007)

working upgrade:

as posting be4, I hand sanded (!) the body enough that any 18650 fits (the AWs are a bit taller but go in and out without problems).
Contact plates are epoxied in.

That whole light was lying around here, because I had no time (and fancy) to put in another sink, emitter and reflector, and
*because I did not read the other posts with enough attention*.

That original circuit works fine on Li-Ions and, for a headlamp, the 2 level output is good enough,
... draws 70 and 330 mA from a medium full Li-Ion. 
The beam from the side emitter is not this great, so at least a quick emitter swap will be made soon, maybe another circuit in the future 
(but to be honest, for me, runtime is much more important than sheer output, in a headlamp)

Only problem is the batt-compartment cap, that is this hard to open, even when barely screwed in.


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