Converting handheld flashlight to external battery pack?

raoulduke101

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Jan 1, 2014
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Hey folks. I am looking to build a waterproof flashlight that is powered by an external 8XAA battery pack. I was thinking of starting with a PT Torrent LED or perhaps one of the Fenix lights. My thoughts were to drill a hole in the end cap or some other part of the light body, install a waterproof wire gland, and then wire the light to the external battery pack. The problem is that I know next to nothing about wiring. I have searched for threads on how to do this, but have not had any luck.

My questions are:

1. Would I need to install some sort of dummy cell and then solder the wires from the battery pack to the terminals on the cell, or can I just solder the wires to the contacts in the light?

2. Are wire glands reliably waterproof? I don't need the light for dive applications, but short periods of submersion are likely.

I apologize if these are dumb questions, but I am a complete newb when it comes to wiring and electronics. However, I have always enjoyed DIY projects and would really like to learn more about electronics. Is there a thread somewhere on here that I missed on how to do this?

Thanks for all the great information on this site.
 

PCC

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Just wondering what it about that light made it a consideration for this?

If I needed a light to be compact and a remote battery source can be used I'd take something like a ThruNite T30 or some other light where the head can be removed and I'd make an adapter that closes the exposed entrance of the head as well as a cap for the now headless battery and wire both adapters together using the appropriate wiring glands. The light can be restored to its origial configuration if needed
 

raoulduke101

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PCC, thanks for the reply. The only thing that interested me about the PC Torrent was the brightness, cost, and waterproofness.

Thanks for the idea on the ThruNite. What's the best way to secure an adapter to the exposed entrance to the head of the light? JB Weld?

I wouldn't need to use the body of the flashlight as a battery holder, because the light will be powered by a common power system in a racing canoe.
 

PCC

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Well, I have a lathe in my garage. I'd just make it out of a piece of aluminum. Now that I know what you are going to use it for that changes things a bit.

There's a flashlight standard known as the P60, AKA D26, that is based around a commonly available light engine. It originated with the Surefire 6, I believe, and is still going strong now. You can get a relatively inexpensive Solarforce L2M or even a P1 host, which is a plastic variant of their L2 series. Then I'd just gut the tail cap, figure out a way to connect up your power wires and put a battery spacer into the body. You'd still need a drop-in, but, there are many varieties of drop-ins available in different voltage and output ranges out there. You might even be able to find an older Surefire weapon light tail cap, as long as it is 6P compatible, and cut the tail switch off to give you an easy way to wire the thing up.
 

raoulduke101

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Thanks, PCC. I checked out Solarface's website. I think I'll order either the L2M or P1 and give it a try.
 

thumpergirl

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May 21, 2013
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Did you ever find a solution? I'm trying to do the exact same thing. P60 host with a drop in, drop should be 1 mode, ~100 lumens for long burn time, and operate up to 15V. Not sure where to find that specific drop in or the tail piece for a 2pin connector. Also needs to be waterproof.
 

mousehunter

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Just a bump to a dead tread, looking to do the exact same thing, for probably the exact same reason-Texas Water Safari.

currently looking at a solarforce 1-cr123 body, a tailcap with a remote switch, and a spacer. Will try to splice power into the switch wire first, if not, the tailcap has a small hole to route the power cable through. But seeing if this wheel has not been invented first. Oh, malkoff dropin.
 

Keitho

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Just a bump to a dead tread, looking to do the exact same thing, for probably the exact same reason-Texas Water Safari.

currently looking at a solarforce 1-cr123 body, a tailcap with a remote switch, and a spacer. Will try to splice power into the switch wire first, if not, the tailcap has a small hole to route the power cable through. But seeing if this wheel has not been invented first. Oh, malkoff dropin.

Damn, Texas Water Safari looks epic. Four nights out on the canoe with no resupply allowed? That's a lot of light that you'll need! Out of curiosity, are you planning on solar recharging battery packs during the days, or will you just swap battery packs?

Your post made me think of a cool project for some of my old hosts lying around, making them work with external battery packs. I might use them on my bicycles, or make some mini spotlights that I could use on DC power or battery packs. My first thought would be to buy or harvest a switch only (not including the aluminum housing, just the switch), then solder the battery pack leads and the switch directly into the head of the light. Then, use potting to make it all waterproof. The metal behind the head is only to house the battery, and provide a little cooling, so why not eliminate all of that weight and bulk (if soldering and potting are within your abilities and you have enough time during your extensive training schedule)?

Since it looks like you're doing extensive portages during the TWS, keeping the weight of the light and battery low might help you out, so I might consider using a driver/head that doesn't over-drive the LED's, so you can keep the LED's running efficiently (cool), and keep the battery pack as light as possible.

Best of luck!
 

thumpergirl

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Just a bump to a dead tread, looking to do the exact same thing, for probably the exact same reason-Texas Water Safari.

currently looking at a solarforce 1-cr123 body, a tailcap with a remote switch, and a spacer. Will try to splice power into the switch wire first, if not, the tailcap has a small hole to route the power cable through. But seeing if this wheel has not been invented first. Oh, malkoff dropin.


Mousehunter - I figured out how to build them for TWS. I've been doing it for several years now. Happy to walk you through the process if you want to take a stab at it, or I also sell them for those that don't want to. hit me up at txgreenroot at gmail.
 
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