# Mod Spark ST6 or Zebralight H600 to Run Off a Battery Pack?



## spelunkik (Dec 14, 2011)

All you electrical engineers out there, I need your help to tell me if this idea is fundamentally flawed: _modify an ST6 or H600 to run off of an external battery pack_.

I am not too knowledgeable about the inner workings of an ST6 or H600, or what voltages/currents these two lights are compatible with. Stacking up 18650s in parallel will keep the voltage constant and multiply the current, right? And the LED regulation circuits should be able to accept increased capacity as long as the voltage remains constant, right?

I think putting it together would be the easy part:

Drill a hole in the tail cap.
Place a waterproof cord grip in the hole.
Feed the cord of the battery pack through the modified tail cap.
Wire the cord to the positive and negative of the light.
Put the tail cap back on.
Tighten the cord grip.
I have interest in using an external battery pack because as a caver I use my headlamps for extended periods of time (12 or more hours of constant use is not uncommon), and the less battery changing the better.

Any help/advice is much appreciated. Thanks.


----------



## B0wz3r (Dec 14, 2011)

I'm not electrical engineer, but IMO modding a light like that for external battery use is just asking for trouble. You're creating all kinds of opportunities for water ingress and other crud to get inside the light.

I've just started to get into caving myself. So I'd love to read any info you want to share about it would be great. 

So far my most demanding outing (inning?) has been at Lava Beds National Monument, this past summer with my wife and kids. My son and I did a couple of their 'advanced' level caves; Hercule's Leg to Juniper, and The Catacombs.

http://www.nps.gov/labe/planyourvisit/loader.cfm?csModule=security/getfile&PageID=183869

While none of it required any rapelling or the like, we did spend most of our time belly crawling, and Catacombs especially is a squeeze... maximum ceiling height most of the way is only about 24". There were also several spot where we did have to free climb down from one level to another, and worm through some tight spots to transition from one tube to another. In some spots, my son had to go first, and I had to take my pack off and push it through to him because I wouldn't have been able to get through with it on. 

I used my Spark ST5-190nw most of the time, and it worked great. I also found carrying a handheld was very useful too. I used both my Zebralight SC50w+ on a wrist lanyard, which I'd just tuck into my sleeve when I didn't need it, and a strong thrower in a holster on the strap of my pack for seeing down long straight sections and the like. Even when in the larger caves were there are prebuilt paths and you can walk upright the whole way, like Upper to Lower Sentinel, I found using the handheld thrower to be a lot more useful than relying on my headlamp.

I've used a headlamp with an external battery pack before, and even though I wasn't caving, I found no end of aggravation and annoyance with the cord constantly catching on something. I've learned that hardcore cavers seem to like overkill in their light usage, but 65 lumens for 18 hours from a single 18650 with the H600 isn't enough brightness and run time for you? While I'm the first to admit my caving experience is limited, I found the 36 lumens of the medium 1 setting on my Spark ST5 to be plenty of light for what I was doing at Lava Beds. When I needed more power, I resorted to my hand held thrower. I prefer that too because a powerful light on my head, even just the 200+ lumens of my little Spark, gives me terrible tunnel vision. But as I said, I'm a newbie at caving, and eager to learn more, and find more places to go, so any info you want to share would be welcome.


----------



## spelunkik (Dec 14, 2011)

I agree and disagree that adding a hole would be detrimental to the light. Yes, you are creating a new potential point of failure, and additional points of failure are undesirable. However, there are many potential points of failure on any given light. It all depends on how likely that potential point of failure is to cause a failure, if the positives outweigh the negatives, etc.

In my opinion, if you drill an appropriately sized hole, choose the appropriate size and proper type of cord grip, there is no reason to expect your light will be compromised. Many cord grips are IPX rated, so you can choose the level of protection.

There are quite a few examples of custom lights out there that use cord grips, even some that were built specifically for caving (the Serv-light, Rude Nora and Scurion to name a few). The Rude Nora has been used by cave divers (for those unfamiliar, that means caving underwater), and it is reported that none have leaked so far. In addition, the Rude has been tested in a hydraulic pressure tank and simulated a depth of 50m (6 bar) for 1 hour, and then at 100m (11 bar) for 1/2 hour. The Scurion has been around for a long time as a caving light and people pay a lot of money to have the "perfect" caving light, so if the cord grip was a great concern this would have been eliminated by now. 

Cord grips are not necessarily detrimental to a light. You just have to install them correctly and don't subject them to excessive abuse.

As I said, I both agree and disagree. I've told you why I disagree... now I'll tell you why I agree: things can _and do_ go wrong, especially when you're underground. Needless to say, you don't want things going wrong underground; even the smallest things can be deadly. Anyway, water, mud, dust and excessive abuse to equipment (and yourself) is the norm. If you have an exposed weak point on a light like a cord grip on the side of a housing, it will eventually fail. This happens all the time on Stenlights, which are one of the most popular and trusted caving lights out there (if they used cord grips this probably wouldn't happen as often). This is why, if I chose to install a cord grip on one of these lights, I'd make it a habit to keep an eye on this weak point. I'd also probably carry along with me an unmodified tail cap so that I could just pop in a cell and separate the battery pack if the situation required it (e.g. the cord grip failed or I knew it was going to see a lot of water or abuse).

----------

As for caving itself, I'm afraid it is a subject that is far too involved to discuss in a single thread, and besides, I wouldn't want to bore anyone else. It is always pleasing to hear of a newcomer's first experiences underground though, and it sounds like you had some good fun at the Lava Beds. Never been there myself. If you have any specific questions regarding caving, feel free to PM me and I'll do my best to answer. You may also find http://www.caves.org and http://www.cavechat.org to be great sources of caving information. Safe caving!


----------



## robostudent5000 (Dec 14, 2011)

as long as the input voltage is within the range the light was designed for, it should work. try it and let us know how it works out.


----------



## spelunkik (Dec 14, 2011)

I think you're probably right Robo. I want to make absolutely sure that it won't damage the light before I try it. This may not be possible to know though without taking the risk.

B0wz3r, I forgot to answer your question. Yes, 65 lumens for 18 hours is both impressive and all that I'd ever really need. That said, more is always better, and an external battery pack would give me truly epic runtimes that would make any caver jealous.  Yeah, sometimes external cords can be a pain. I've had to put up with them for so long that I just accept the occasional nuisance.


----------



## skyfire (Dec 14, 2011)

im not sure what would happen.
but XM-L are designed to run 3 amps max. 
i dont know how the drivers are designed, and if the current will be regulated. you might have to find and try a driver that is set up for the application you want to run.

ST6 seems to be a much easier platform for modding compared to the zebralight.

instead of modding it, how about a 2 headlamp setup?
its what i do at work, i carry my spare batteries in a spare light. :thumbsup: so if something happens to my main light, i just pull out my spare without missing a beat.


----------



## BarryH (Dec 14, 2011)

That should work ok Spelunk. If you want to increase run times you could wire more of those 18650 cells in parallel which will keep the voltage the same(won't damage the light) but increase the Amp Hour capacity. Two or three cells (or more) in parallel should give you approximately two or three times (respectively) the run time of a single cell. Or you could use a larger size/capacity cells with the same voltage and higher Ah rating in your external battery pack. 

In addition to making the modified end cap water tight, be sure the cable grip and cord are rugged enough to survive scrapes, snags, etc. without being pinched and shorted, or otherwise pulled loose from the light or battery pack. I would also carry another, smaller, extra head lamp or two for backup. Especially if you are doing deep exploration.

Years ago I used to do a bit of cave diving in the underwater springs and aquifers of north Georgia and the Blue Holes in the Bahamas. I carried a large primary light and 3 or 4 smaller smaller back up lights for redundancy. My primary lights were custom built and had large external battery packs that were also great for powering lights used for underwater video photography. Bulk and being streamlined was more of a concern than weight since they were designed, or modified, for neutrally bouyancy in that application.


----------



## B0wz3r (Dec 14, 2011)

spelunkik said:


> I think you're probably right Robo. I want to make absolutely sure that it won't damage the light before I try it. This may not be possible to know though without taking the risk.
> 
> B0wz3r, I forgot to answer your question. Yes, 65 lumens for 18 hours is both impressive and all that I'd ever really need. That said, more is always better, and an external battery pack would give me truly epic runtimes that would make any caver jealous.  Yeah, sometimes external cords can be a pain. I've had to put up with them for so long that I just accept the occasional nuisance.



No worries, and thanks for the links; I'll check them out as soon as I can.

I understand the whole gear thing... I've been a cyclist for many years, and you see that kind of thing among road and mt. bikers too... "check out my new light"... or "check out this sweet new derailleur I got"... etc. 

Hard earned experience has taught me some valuable lessons, and I've learned a few simple rules from various calamities and mishaps I've gotten myself into over the years, based on many years of being a cyclist (12 of which I did not own a car), lots of backpacking, hiking, and camping. Now caving too. 

One, as you mention, Murphy's Law... anything that can go wrong, will. 

Another I learned back when I was in college from some friends who were active mountaineers; 'take care of your gear, because your gear takes care of you'. The corollary to that is a quote from Amundsen (discovered the S. pole); "there's no such thing as bad weather, only bad gear".  They were what got me into backpacking.

Of course, the classic saying from here at CPF and other tool forums I read "two is one, one is none". So I always make sure to have two of everything I consider essential for surviving outdoors should I end up needing to; flashlight, headlamp, multi-tool, swiss army knife, etc.

So when it comes to doing more caving, I think I'll be okay for the most part... it'll just be a matter of getting and learning to use the gear, and what the standard safety procedures are. My first gear acquisitions will be for a coverall, helmet, gloves, and some pads. I've got plenty of lights and other equipment that should cover me until I'm ready to start learning how to do climbing and use ropes and the like. 

Anyway, I'm rambling... sorry.  Thanks again for the info. There's a small core of us that post regularly here on the headlamps forum; me, Bolster, Robo, Psychbeat, Varuscelli... and a few others I'm sure I've forgotten. We like to stick together and we help each other out a lot. So welcome to the headlamps forum!


----------



## kevinm (Dec 15, 2011)

I understand your desire, but it's a bad idea. The beauty of a Spark ST6 or a Zebralight is that there is no external battery pack. Battery packs, unless done really well, are likely points of failure. You could add a cable gland (the name for the "cord grip"), but it'll be less waterproof and more prone to failure than the original. Doing the battery pack correctly will cost $60-$100. 

If it were me (and I cave most weekends in CO, where all is tight and grabby), I'd buy two Sparks or Zebralights. Then, you have a backup, twice the runtime, and you don't have to change batteries. Or buy a better (but more expensive) caving headlamp (and a backup).

Happy cavin'!


----------



## Henry50 (Dec 15, 2011)

imo its very plausible. imo buy an off the shelf battery pack, and a AAA to CR123 adapter (or whatever your torch is), and just modify it? I suppose you'll need to drill a hole in the battery compartment, imo do it in the side, that way if it did much up, you could reseal the hole sith silicon and be done with it. As for water ingress, just use existing parts, silicon and consider dipping in rubber. Perhaps though, after all this time and effort, its easier (and cheaper) just to buy an existing model


----------



## mikedeason (Dec 15, 2011)

I just always carry 2 extra 18650's in my pocket.

Changing out the battery takes about 20 seconds.


----------



## spelunkik (Dec 15, 2011)

Thanks for all the unique responses! This gives me a lot to think about. If you couldn't tell, I am not fully committed to this idea yet, so I really appreciate some of you expounding on the negative aspects to this idea. I am still seriously considering following through with it, but there's still a chance I'll abandon the idea completely. Perhaps I'm getting too far ahead of myself... I haven't even bought one of these yet.


Yep, it is more or less a cardinal sin to go underground without at least three reliable sources of light, and I usually try not to break this rule. If my modded light failed on me, I'd just quickly switch to my back up which is also on my helmet.

True, it doesn't take long to swap batteries, but are your batteries stored deep within a muddied, tightly-packed pack?  Trust me, by the time it's all said and done, it's quite the inconvenience, at least for me it is. Also, sometimes there are very few places in the cave where stopping is convenient. I guess such a scenario could be avoided with proper planning, but it's nice to not have to worry about it.

Again, I'd try to acquire a second cap so that I could choose if I want to use the external pack or not. I agree that a huge advantage of these two lights is that they don't have an external pack. That said, I don't mind external packs if it means increased runtime. In addition, custom cave lights are EXPENSIVE. using an ST6/H600 as something to build upon, I'll have a light that performs on a level or above that of current lights, and only at half the cost. Yeah, I could just build the light from scratch, but I'm not really saving money by doing it that way and Spark/Zebra can make it much more durable/smaller than I could.

Buy two lights? Hmm... that is a more expensive option, but quite tempting. Maybe a H600w coupled with the flood of an SD6-460NW?

Sounds like in theory modding one of these two lights will work. Great news!! 

Thanks for the warm welcome. I hope to positively contribute to this forum.


----------



## kevinm (Dec 15, 2011)

spelunkik said:


> Yep, it is more or less a cardinal sin to go underground without at least three reliable sources of light, and I usually try not to break this rule. If my modded light failed on me, I'd just quickly switch to my back up which is also on my helmet.



That's one I hold sacred. I've seen StenLights and Scurions fail. Always have 3.:thumbsup: 




spelunkik said:


> Buy two lights? Hmm... that is a more expensive option, but quite tempting. Maybe a H600w coupled with the flood of an SD6-460NW?
> 
> 
> > That sounds like a great option! Alternately, you could go with 2 of the ST6's, one with the flood lens and one with the clear. That way, all the parts are interchangeable, in the terrible off chance that you need to do that.
> ...


----------



## eh4 (Dec 15, 2011)

first get extra tail cap. carry un modified tailcap an extra batteries with you. 4 the modification use a hollow threaded tube through the hole, then gaskets washers and nuts to provide shoulders on inside and outside for leverage resistance. make a dummy battery plug that threads on to the inside of the threaded tube with a spring at the + end... now you've got an unmodified light and a modified tail cap adapter ready 4 battery pack.


----------



## joanne (Dec 16, 2011)

I haven't had the opportunity to explore a cave in a lot of years, but I have been active in mine exploring for the last few. This is my "new" light that a friend over in the UK made up for me. It's based on an Oldham mining lamp that has been upgraded to LEDs. Each of the emitters have three output levels, then the two 5mm emergency LEDs are hooked up with resisters only. The battery pack is 3x18650 for some nice run times. (I haven't tested the run times at various power levels yet.) I purchased a Turnigy Accucel 6 charger so I can recharge off of the truck battery when we are on multi-day trips.

The "naked" emitter projects a beautiful flood that I have fallen in love with. The spot beam is available when I need it, but the flood is just wonderful. I finally understand all of the fans of flood lamps on this forum! 






The battery pack is held on with elastic bands. I keep an extra battery pack in my pack.






The rotary switch on the right side of the lamp allows LED selection and power setting adjustment. 






My thoughts on redundancy are this; If you are walking or crawling on level ground then having to dig in a pack for a backup light would be an inconvenience. If you are rappelling or climbing a rope, not having a helmet mounted backup light could quickly become a life threatening situation. I usually have two helmet mounted lights, one "thrower" in my pocket, and a backup headlamp in my pack. Just like a parachute for a skydiver or a regulator for a scuba diver, an underground explorer's light is a piece of life support equipment.

*Joanne*


----------



## davidt1 (Dec 16, 2011)

Joanne,

Nice pictures! I bet that's one useful helmet light.


----------



## spelunkik (Dec 16, 2011)

Eh4, you and I are thinking much along the same lines. I would probably try a cord grip first, but if it seemed shoddy in terms of leverage then I'd try your idea. I think the hard part would be acquiring a second tail cap. 

Does Zebralight sell individual components??

Joanne, that is one fine light there. Do you notice any overheating on the high settings? As a suggestion, you may want to try flipping the battery pack the other way so that if it somehow starts slipping the cord will catch on the elastic bands, preventing further slipping. Do you know what kind of emitters those are? From this distance, they almost appear to be XM-Ls. What about the current to the LEDs (or theoretical lumens)? The two 5mms are a good idea, especially if the flood/spot driver(s) don't have a very low mode. The fit and finish is also quite good.


----------



## eh4 (Dec 16, 2011)

to tell you the truth I've been thinking of doing just about the same thing for a while.
I'm also waiting for the Neutral tint version of SC80 AA/CR123 to come out,
since the head screws right off for the AA to CR123 adapter it's basically a plug and play light just waiting for a threaded adapter... and the light is designed to handle voltages from depleted AA to full charged lithiums. 
My thinking was that once it was all worked out and I had a waterproof new threaded base made up, that with sealed/hydrophobic power plugs it would be a simple enough matter to make up a couple different lengths of cord and different chassis, for bike or helmet, etc.


serious looking headlamp Joanne, battery pack is inspiring. if they are 3000mAh 18650s then the pack is about the same capacity as 13-14 eneloop AAs, I think.


----------



## offroadcmpr (Dec 18, 2011)

You may want to look into mountain biking lights. Many of them are now using XML LED's and have external battery packs. They are also designed to attach to a helmet and are generally pretty durable. Plus since many are designed with a external battery pack you should in theory be able to build your own pack with more cells if desired. 

They are usually rain proof, and some may be able to be fully dunked but it would probably depend on the model. The only problem I can see is that many are not very low profile because it is generally not necessary while biking, but in caving it usually is. I have done some caving squeezes where it was easier to take my helmet off to fit through it!


----------



## spelunkik (Dec 18, 2011)

That's a good thought offroadcmpr, and I have already looked into bike lights. Bike lights are very appealing because many of them have admirable outputs, and in some cases good runtimes. Unfortunately, as you've said, most are not technically waterproof. I don't think rainproof would cut it. There may be some out there that are totally waterproof, but the ones I've seen in my price range (0 to $200) aren't. As you've also said, they tend to be on the bulky side, but with an H600 setup it should be relatively small.


----------



## Barrie (Dec 19, 2011)

have you though of getting one of the ZL clones as a prototype 
ultra-fire do a hole range of them some can be had for under $30 that way if it didn't work out you haven't ruined a $90 ZL 
and if it dose work you have a backup
just a thought


----------



## spelunkik (Dec 19, 2011)

That's not a bad idea either Barrie. Of course, such a prototype wouldn't prove compatibility with Zebra circuitry, but at least it would demonstrate how well the cord grip idea would work. I wonder how easy it would be to upgrade the LED in the ultrafire...


----------



## psychbeat (Dec 19, 2011)

Ive got one of KevinMs p60 headlamp hosts on the way
and will do a short review of it sometime later this week.
Ill probably be running an 3.6amp neutral XM-L in it mostly
until I get a more powerful module.

but basically it will be like my spark st6 nw with a 4X18650 1s4p
battery pack. only 3.6a is quite a bit brighter than the sparks "super"

4x18650 (3100mah each) will provide plenty of runtime.

other than the fun of tinkering and building your own light I think
that something like this would be the better route to go.
custom drop-in modules are fairly cheap too from vendors here 
with lots of options for emitter ,tint ,UI etc.


----------



## ToyTank (Dec 19, 2011)

I think the ZL clones are cheaper but your not going to get the premium emitters, super efficient circuits etc you get what you pay for.

Caves I have been in are 99% tight quarters and IMHO my ZL H60 moonmode or low are best to preserve night vision. The H600 is brighter and more efficient I think running low or medium is PLENTY of light without blinding yourself or partners too bad. So pack one spare 18650 and I think your golden. That being said I dont have hands on with ST6 or even know much about it. A


----------

