Skilhunt H03 Headlamp Mods for Waist Light

xcandrew

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Re: 18650 battery pack assistance needed.

This might be something you already know, but with homemade battery packs and running, you'll have to be very careful with strain relief and good cords. Do not underestimate the fatigue failure potential of cords when running and when the cord is basically unsupported between the lighthead and battery pack. I had a long learning experience when I was running a homemade external battery setup on my Princeton Tec Eos more than a decade ago, where I'd have the cord break every several days, and then I'd make improvements with different cables, shrink wraps, and strain relief setups, and then keep reiterating and fixing stuff. Then cords that kept breaking on the then new Magicshine 808 P7 lights half a dozen years (?) ago (though the bikers that used the light didn't have the same complaints). Now I just use an off the shelf setup and prefer to keep the battery pack on my Yinding/Gemini on the back of the headstrap so there isn't cable flapping around.

The bounce with every footstep when running, especially when the battery pack is on your body, puts way more flex cycles into the cords than use on a bike for example. Not sure how your waist belt setup will look like, but be careful of unsupported cord. Make sure the strain relief isn't too stiff so the cord breaks at the edge of the strain relief. Not that you'll have this problem, but something as little as the extra stiffness of the solder on a repaired cord that is bouncing around from running, even with good heat shrink on it, will produce a stress riser that will cause an eventual failure, at least for the typical 22 AWG cords used in lights like Magicshine/Gemini/Gloworm. Why not just get an off-the-shelf battery pack? You can get 6 and 8 cell packs from Magicshine or Gemini. I'd personally just get two off the shelf 4 cell batteries if you need that capacity, so if one fails, you still have another. Switching between batteries can easily be done on the run.
 
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ThinAirDesigns

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Re: 18650 battery pack assistance needed.

Thanks for the input xcandrew.

Excellent points. I have many years of design experience in the motorsports fields where vibration and fatigue are primary reasons for failure. The fewer cables and connections, the fewer failure points -- all true.

As to the "why not just get an off the shelf battery pack?" question, the answer is multlilayered, but here is the biggest one:

I don't want to carry any more than I have to when running 75 miles unsupported through steep, technical mountain terrain. I have found none of the commercial packs you mention to be using anything close to the high capacity cells that have been available for some time now. For instance, the Magicshine MJ-6036 uses 6 2200mah cells and weighs 18oz. I would need to carry 4 of those (for a total of nearly 5 lbs of battery) to feed my light for the needed 14 hour stretch. The bare NCR18650b cells for that same capacity weight barely over a pound and a half and I certainly can package them quite nicely with a one lb budget -- cutting my battery weight by basically half. Carrying an extra 2.5lbs over 54,000ft of vertical change (my next running challenge) is what we call in engineering ... "less than ideal". :)

(and as an aside, on the terrain I'm running, switching between batteries "on the run" is definitely not practical)

Thanks again -- your concerns are well thought out and valid.

JB
 

dirkomatic

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Re: 18650 battery pack assistance needed.

What did you end up using for a battery pack? I would like to make something very similar for mounting on a helmet, but it would need to withstand wet conditions. It seems the 4 cell pack is easily found, but I really would like a 2 cell pack which can easily swap out 18650s.
 

ThinAirDesigns

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Re: 18650 battery pack assistance needed.

What did you end up using for a battery pack? I would like to make something very similar for mounting on a helmet, but it would need to withstand wet conditions. It seems the 4 cell pack is easily found, but I really would like a 2 cell pack which can easily swap out 18650s.

Depends on what you mean by "wet". I purchased two of these to use for my shorter runs -- I have no qualms with them in the rain, but wouldn't want be ducking through sumps in caves with them.

946959d1418678404-c-b-seen-upgradable-2-cell-helmet-battery-case-review-cbseen-73-.jpg
 

dirkomatic

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Jun 28, 2016
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Re: 18650 battery pack assistance needed.

Caving is what I would be doing... I saw those c & b seen packs. Is there a US source for them?

Maybe I'll just stick to the two light setup.
 

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