# Battery Box for Helmet Mount



## Tobias Bossert (Jan 2, 2011)

There are many headlamps out there. Only a few are ruggedized sufficiently to suite caving expeditions. This is not only a question of the headlamp but of the battery compartment too. Using Li-Ion rechargeables you need a safe mechanical protection of your batteries.



For example Scurion provides a very good aluminium case to be mount at the back of the helmet. You can change the internal Li-Ion rechargeable (packs with 2 or 4 cells 18650). Unfortunately this enclosure can be ordered in a set with the whole lamp only.



Stenlight and others make very nice headlamps, bomb proof with respect to the headlamp but not with respect to the battery compartment. They use Li-Ion rechargeables in stable heatshrinking sleeve. This may be water proof, but it is not mechanically safe with Li-Ion under rough cave environment.



Petzl offers a yellow battery case with Petzl Duo 14. This casing is sold with a holder for 4 AA cells or with a 4 AA rechargeable NiMH battery pack. It is not compatible with those commonly used Li-Ion 18650 rechargeables.



Petzl additionally offers Li-Ion rechargeable batteries with 2 or 4 cells 18650, each pack providing its own enclosure. This is nice, if you need only one of them. This is expensive and unpractical, if your expedition is long and you need to change batteries sometimes.



Twenty years ago Petzl sold carbid lamps with additional electrical light. Those old battery boxes were very simle and very usefull.







They could be used with a 4.5V primary battery or with a holder for 3 AA cells. They were quite 'low tech', the weight was 40g only and they had two injection moulded ABS shells hold together with a piece of bicycle inner tube.



I'm looking for a more universal battery box to be mount at the rear of the helmet. It should be strong enough for caving environment and big enough to hold either a 4 pack of 18650 (side by side) or a holder for up to 5 AA cells. This means the inner dimensions should be about 80 x 80 x 22 mm (this is roughly the same size as the old Petzl box).



Does someone know such a tough battery box? 

Please give me advice where to order them.



*If nobody knows such a universal box, is there any interest on such a device?*



For example it could be done like the schematic drawing:






The main part could be injection moulded ABS 1.5 to 2 mm thick.

The opening is downwards. The plug could be made of rubber or silicone. Alternatively we could use an inner lid made of plastic somewhat softer than ABS. Anyhow, the plug/lid will be hold in place by a piece of bicycle inner tube like the old Petzl construction was. The cable will feed downwards through the plug/lid.



The inner parts (cable, feedthrough, electrical plug or contacts, holder, foamrubber to avoid clattering) would be up to the user.



If there is any interest in such a low priced tough battery box, please post the dimensions needed. If at all, there would be manufactured one size only.


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## horselfy (Nov 3, 2013)

did you ever source something suitable for this?


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## uk_caver (Nov 4, 2013)

I'd be interested in something like that.
I'm currently still buying suitably old Zooms off ebay to get hold of Petzl battery boxes like the one mentioned above (though I'd always assumed they were made from something like polypropylene, rather than ABS).

Personally, I prefer to use releasable cable ties for holding boxes closed, rather than a rubber strap, since rubber has a nasty habit of being brittle (in the sense of having little resistance to crack propagation), and small nicks can fairly quickly lead to complete failure.


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## STiFTW (Nov 4, 2013)

I would be interested, and will add a suggestion for a rubber seal and weather proof wire to go through. I do a lot of biking in inclement weather.


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## Szemhazai (Nov 4, 2013)

You have to remember that 4x18650 will weight about 200g, rubust sealed box another 100 -> almost 300g.

Also there is a wiring problem 1s4p, 2s2p, 4s1p ? I suggest to use as internal part, or fit in one of the commercially available battery holders inside.


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## uk_caver (Nov 4, 2013)

200g is certainly bearable - I normally use a NiMH pack made from 3x18650 (or one of the 8 or 10 NiMH cell sizes that is within a mm or two of 18650), and they aren't vastly below 200g.

Though if I went lithium, I'd probably go for a 2-cell or 3-cell pack, since I don't run a ridiculously bright light.

Personally, I reckon there's a lot to be said in favour of caving lights using ~3.7V power - it's easier to build in redundancy or to have multibeam lights with compact circuitry when the input voltage is a decent match for the LEDs, easy to run from Li-Ion packs of any number of cells, and easy to use various NiMH power sources (or even alkaline as backup) without having silly numbers of cells.


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## horselfy (Nov 5, 2013)

I'd be interested also.


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## horselfy (Nov 6, 2013)

For what its worth, I bought this battery box a number of years ago to use with a SpeleoTechnics Nova. Its designed for a flatpack battery but I'm told it will fit 4 18650's. Connector looks rugged, but the case itself would need some waterproofing. Can't seem to find a source for them now.


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## uk_caver (Nov 6, 2013)

I never really liked those cases.

Having the helmet mounting being by the strap which also held the box closed did mean that slackening of that strap was more than just annoying, even though it could be backed up with cable ties, and even slight slackening could exert forces on the plug which caused dubious connection.
The voltage drop from the inbuilt diode was a unfortunate, especially in the days when LED Vfs tended to be somewhat 
higher.
Given the similar width+height to the old Petzl boxes, they seemed to have less space inside apart from being deeper (in the sense of 'height,width+depth') since they were variants of boxes that used to hold 3 cells of C size (or some close approximation to C size).

I guess if an 18650 pack was made up with staggered cells that might make some use of the thickness (or is that depth?) of the case.


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## Mooreshire (Nov 7, 2013)

Sir Lord John Biffington IV over at CustomDuo/LittleMonkey sells just the battery boxes from his _Rude Nora_ headlamp for DIY use at £70 apiece. They are sized to fit shrink-wrapped packs of 3x 18650 cells. The new Rude Nora 2 lamp's box is slightly smaller and holds only two cells, but I'm not sure if he's selling that one for DIY yet.





(Photo jacked from customduo.co.uk)


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