# DIY 18650 battery holder successes and failures



## radaroven (Apr 26, 2009)

I've been lurking in this forum awhile and learned many things of considerable use to me. I thought it might be time to contribute a little by sharing some of my learning experiences, especially since, except for a fugly light thread, there's not too much in the way of postings of things that didn't work out, which would also have been helpful to me.

First up - battery holders, mainly because this turned out to be the DIY light thing that consumed the most time for me (more than the light heads in the end), and had the most false starts and revisions and was the source of the deepest (such as they were) frustrations.

I really like the idea of using individual cells instead of soldered up packs, even though it's kind of less simple overall than a single pack - the ability to charge cells as needed or just replace a defective one is really positive, as is the cost of cells and cheap chargers from DX. I started out with 18650s as the way to go, even though I have lots of NiMH AAs, the total weight for the sorts of lights I was thinking of building up was starting to look on the high side, and the prospect of charging 20-odd batteries after a ride wasn't too attractive.

I balked slightly at turboferret's (and later sdnative's) resin holders, they look really really really good, but turn out to be pretty costly by the time they turn up in our part of the world (especially given our appalling exchange rate with any currency stronger than the Turkish lira), so DIY quickly became the vehicle of choice. Resin casting is a bit too technical for me at present, so other simpler options were needed.

I started out thinking I needed a 4-cell holder, then 5, then it became 7/8 as light designs evolved (and also a triple); this was of course hopelessly inefficient, and there's a lot to be said for working out the brief before laying in to the tools. I thought I'd make contacts too, which worked ok initially, but the standard spring steel contacts were so much better than my crude DIY ones in the end, that the two most successful designs were made around the contacts.

Each battery holder version got more simple, and Mark IV is very simple indeed.

I'll apologise in advance for the pics, all shot late at night under a desktop fluoro lamp, nothing but trouble for the camera, and all sorts of intriguing tints as a result...

*Mark I*
Tube arrangement, following on from http://forums.mtbr.com/showthread.php?t=457070. I used alupex tubing (gas and water supply tube with an aluminium core sandwiched in poly-something, finished with electrical conduit end caps.

Positives - tough and secure and fairly easy to put together. The end caps are a tight friction fit onto the tubing, no danger of working loose. One length of tube is a pretty good protective solution for 2 - 4 cells and easily attached to any shape of frame.

Negatives - costly (caps cost more than the tube and the tube was expensive to start with) and the wiring was a bit awkward because I didn't have the energy to work out a detail so winding on the tube cap didn't wind up the wiring. Clunky if in more than one length, and more difficult to mount (probably would work well if two tubes were clamped together). And heavy. Also needed to wind electrical tape around the cells to stop them jiggling too much, which meant they ended up a really tight fit in the charger...

There are a few versions of this sort of thing on these forums, all better than mine in meaningful ways.









*Mark II*
Slightly too-clever attempt to fit 4 cells into a mustard tin (2 tins ganged together for up to 8 cells was the plan). Made up contacts using shaped bits of blank circuit board (cut out and sanded the traces, following an idea in a post I've lost the link to) to isolate the electrical path from the tin, soldered on little copper tabs to touch base with the batteries and tinned everything - fairly good in concept, but I had a bit of a mechanical issue. Would have worked well if I could work out an easy way to fix the lid on really firmly - the way I had it, I couldn't get enough pressure for the contacts to function properly. More time (and cleverness) would probably solve this problem.

Positives - mustard tins are pretty robust, nice tight fit for 4 cells in whatever configuration, rectangly shape is pretty easy to mount to bike just about anywhere. Base materials pretty cheap too.

Negatives - contact system turned out to be far too complex and time-consuming to make, and ultimately not really effective due to mechanical problems with the rest of the system, final frustration level overly high.
















*Mark III*
Following itess's nice and simple idea http://itess.simpix.us/8-18650-holder and http://itess.simpix.us/battery-case-4-18650, I glued up some 2 mm styrene using pvc pipe welding cement - two interlocking pieces with two end caps to make up a 7/8 cell holder, with the keystone battery clips.

I pinned the end caps in place with little tenons cut out of paper clips and some epoxy to mechanically lock it all in place, made up a dummy cell/spacer out of a bit of aluminium angle I had lying around and painted over the mess, to achieve a quick and easy 7 cell holder. Strain relief is via some strategic turns of galvanised florists wire and copious amounts of hot melt glue.

After test fitting to my bike, I got worried that so many lithium cells could be a bit vulnerable under the frame (visions of fireworks), so I made a protective sleeve out of thin aluminium, wrapped the whole lot up in a vaguely padded soft sunglasses case and sewed on two long straps to fix to my monocoque frame main tube.

This works really well. It powers a 6x XRE R2 bar light with buckpuck running off the 7 cells. The plug is an AMP Superseal which is pretty bulletproof. The cells are held in with a few offcuts of inner tube - this is very robust and they don't come loose at all, even after a good-quality off-the-bike experience.

Negatives - nothing significant, although getting the plastic to fit nicely and tightly together was tedious because of the small size of the parts and the thickness of the material, and my lack of utter confidence in the glue made more work in locking the thing together - also, I'm still thinking about how it could be made to conform better to my frame. It would go well in some sort of bottle cage adapter thing too.
















*Mark IV*
The joy of thermoplastic materials! I belatedly realised I needed a 3 cell holder for my helmet light and figured Mark III was still too complicated for the amount of time I actually wanted to spend (especially after the first three versions).

I had some 3 mm sanitary grade acrylic lying around, helped by a cold night and a flash of inspiration. 20 minutes later I'd bent up the Mark IV holder and wired it up. 5 minutes of that was heating up the stove because I couldn't find the electric heat gun, and 5 minutes was re-doing the first two bends because I hadn't measured carefully enough. Methodology was to simply clamp the plastic between a couple of flitches of wood and head, forming and setting the bend by pressing it against a cool flat surface. This was the work of moments once I worked out the best way of softening the plastic without scorching my fingers.

Fitting the contacts and doing the wiring and strain relief took only a few minutes. The single longest operation for the whole thing was fitting the plug (Amp Superseal), which is fiddly work at the best of times.

This holder lives inside a soft sunglasses case in a front pocket (on cold nights) or in my pack on warmer nights and powers a 2 x XRE R2 helmet light off a Recom buck driver. The cells are held in with a bit of inner tube, and won't come loose even under heavy persuasion.

Negatives - I cut the battery leads a bit short and could really do with a bit more length. Measure twice, and then have someone else measure before you cut would be a good plan, at least in my case.
















Key components
battery contacts - Keystone 534-209 (via Mouser). The delivery made these fairly expensive for me, but they're worth it.
plugs - Amp superseal. Definitely worth soldering the leads into these, even though they can just be crimped, mainly because they need a bit of energy to assemble and the crimped leads came loose once on me.

I'll post up the lights some time soon once I've found a good spot for beam shots.

That's entirely long enough for one post.

Share and enjoy.


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## OverTheHill (Dec 3, 2004)

Thanks for sharing your experiences radaroven. I find that I am in almost exactly the same position as you I am waiting for my first order of XP-Gs to turn up and so am planning my lights and playing about with battery holder designs as well.

I have considered all the ones you detailed and also a couple of unique designs of my own that I may share at some future time if I can make them work.

Regards,

OTH


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## Turveyd (Sep 30, 2007)

I do like the idea of a long metal cylinder that'll take 4 batterys and the none wired side unscrews for access, hmmmmmmmmmmm Copper pipe time


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## Vancbiker (May 25, 2005)

Turveyd said:


> I do like the idea of a long metal cylinder that'll take 4 batterys and the none wired side unscrews for access, hmmmmmmmmmmm Copper pipe time


My first 18650 holder was a long piece of plastic tube. The battery weight was too much for the spring contact I used and a good bump was all that was needed to open the circuit.


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## radaroven (Apr 26, 2009)

*Tubes are good*

Turveyd - that alupex-type tubing is really good for the tube design. It's a sandwich of two layers of poly-something with an aluminium core. It's a bit tougher than copper and way lighter (and probably cheaper). Total weight with 4 18650s and plastic end caps would be pretty tolerable compared to any other thing you could make.

The tube I found had a bore that was a little too large for the batteries, which then jiggled around and would have given electrical problems for sure if I'd left them. This issue would have been easily solved by running the return wire internally to reduce the bore a little. (I should have seriesed up the two tubes at the same end, but failed to think it through properly and just wrapped electrical tape around the cells to take up the difference which worked well - but it made them a pretty tight fit in the charger...). Then you'd have only one screw cap to undo ever, also a good idea. The plastic electrical conduit end fittings I found were a really tight friction fit and could be permanently anchored in place with a couple of self-tapping screws without trouble.

It would be very important to use or fabricate some quite stiff contacts, or cut the tube length very carefully so that the screw cap compresses the batteries into the contacts as you do it up - preferably both. This would avert the risk of "Vancbiker's surprise" where light at night magically and instantly transforms into darkness with a small bump...

Done right I think this tube design is a pretty bulletproof solution, my main problem with the design was in trying to accommodate 7 cells and a funky frame shape, for which duty it isn't really cut out. Main lesson - identify the best design for the number of cells and where it can fit on the bike before you finish building it...Secondary lesson, it's worth time labouring over the details before picking up the tools...


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## Vancbiker (May 25, 2005)

radaroven said:


> It would be very important to use or fabricate some quite stiff contacts, or cut the tube length very carefully so that the screw cap compresses the batteries into the contacts as you do it up - preferably both. This would avert the risk of "Vancbiker's surprise" where light at night magically and instantly transforms into darkness with a small bump...


Yeah, that system worked great in the driveway. I use the Taskled Flex series drivers in my lights. When the power breaks, they go into a flashing mode for a few seconds that allows you to enter the configuration menu. That flashing while going through a bumpy section is a pretty cool "stop action" strobe effect......NOT!

I think now that a tube layout would be fine if a person used a stiff spring. The spring on a standard battery contact is just not enough. Mounting orientation will also make a difference. I mounted mine with a clip alongside the bottle cage on the downtube. The clip was originally for mounting a pump. If the tube was hung under the toptube (horizontally) then forces from bumps would have less effect on the batteries.


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## ifor (Apr 15, 2008)

Vancbiker said:


> Yeah, that system worked great in the driveway. I use the Taskled Flex series drivers in my lights. When the power breaks, they go into a flashing mode for a few seconds that allows you to enter the configuration menu. That flashing while going through a bumpy section is a pretty cool "stop action" strobe effect......NOT!


You can stop the flashing to enter the menu with a Flex driver if you use the UIB2Q user interface. Combined with seting the Poweron mode so that the light comes on after power is aplied you can get to the situation where a dodgey contact somewhere is not fataly bad.


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## Vancbiker (May 25, 2005)

ifor said:


> You can stop the flashing to enter the menu with a Flex driver if you use the UIB2Q user interface. Combined with seting the Poweron mode so that the light comes on after power is aplied you can get to the situation where a dodgey contact somewhere is not fataly bad.


Thought about that but made a different 18650 holder. So far have not had any problems with the spring contacts and single cells.


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## radaroven (Apr 26, 2009)

Vancbiker, I really like your design and did give the concept serious thought for borrowing, albeit adjusted in a way that I could actually build. It seems a little tricky to implement with hand tools given my current level of fabricating skills, so I didn't end up exploring that particular path.

Like lots of the DIY on display here, the quality looks amazing, to the point where I'm sure you'd be hard pressed to buy anything as well made anywhere, top work.


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## Vancbiker (May 25, 2005)

Thanks for the compliments:blush: . I am thinking about using a design and construction similar to your MK4, but holding 4 cells. I will use 2 of them, back to back, to make an 8 cell holder for my double MC-E light. I will probably use polycarbonate (Lexan) and machine in the pockets for the contacts while it is flat, then heat and bend. The contacts I use fit in slots cut in the plastic. The positive contact is just below flush to the surface of the plastic. That prevents a battery inserted backwards from making contact and causing an accidental short.


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## biketuna (Mar 28, 2008)

nice job VAN, what is the diameter of that holder?


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## Vancbiker (May 25, 2005)

It's 2" in diameter. Here is a thread where the details on it are.
http://forums.mtbr.com/showthread.php?t=501179


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## radaroven (Apr 26, 2009)

Vanc, I dream of such precision, then set to work with hand tools fairly crudely. 

Recessed contact pockets are a cool solution to the classic "now which way round does the battery go" problem. Unfortunately for me, milling isn't currently a viable making process, and I suspect its beyond my present ability to achieve the necessary tolerances to make a workable version of that detail. Although I could maybe make up a metal bending jig to improve the accuracy of the folds by an order of magnitude, then maybe I'd have something nearly accurate enough to work with. 

Thinking about other ways to achieve the same result, I wondered vaguely about putting a wee diode in each of the links between the contacts - put the battery in backwards and no power flows. This might be on the easy to execute side of the spectrum, which is advantageous... Anyone know if there's a good reason not to think about doing that?


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## snowpanda (Oct 5, 2009)

radaroven said:


> Thinking about other ways to achieve the same result, I wondered vaguely about putting a wee diode in each of the links between the contacts - put the battery in backwards and no power flows. This might be on the easy to execute side of the spectrum, which is advantageous... Anyone know if there's a good reason not to think about doing that?


Voltage loss. A 0.7V drop across a regular diode on your 3.7V cell is a _*big*_ percentage loss.
Schottky diodes can be down to 0.2V which would be more acceptable (though their reverse leakage is higher - is it so high that it would be a problem??)
There's probably some other really good reason out there which someone with better knowledge can supply......


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## radaroven (Apr 26, 2009)

That's reason enough.


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## dotori (Nov 12, 2009)

radoraven, I like something close to mark 4 built in a mark 3ish way. Cutting styrene doesn't involve burns. Thinking about buying some styrene now. Dumb question from a noob at this, what connector is that on your main leads?


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## radaroven (Apr 26, 2009)

No burns needed, the heat required to soften the plastic is on the low side. An ordinary hot air gun is quite sufficient to form the bends in the styrene or acrylic, helped along with a couple of pieces of squared timber and some clamps to ensure straight fold lines.

The thing I really liked about the formed bends (esp. compared with Mk III) is there is no potentially fallible glue joint to worry about and no need for mechanical reinforcement of the joint, plus the natural springiness of the plastic can be used to help hold everything in place securely (I put a slight camber in the plastic to add tension in to the battery contacts, worked a treat). 

The connector is an AMP Superseal (there's a thread somewhere in the forums that led me to those). These are car parts. They make a very positive and pretty water-resistant connection that can't accidentally be disconnected or vibrate loose (but are a bit fiddly to assemble initially). I think they're overkill for this sort of use, but am pleased I've used them when I look at other options available in our part of the world...The mini-Deans style plugs are probably entirely sufficient unless you're planning on regular underwater work...


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## dotori (Nov 12, 2009)

Thanks. I like the look of the connectors, that's the main thing. Deans just don't look nice. SAE look ok to me too, it's also an auto connector. Today when I get my charger, I'll be using what I have for now... crimp on paddle connectors. 

sound like thermo might be worth a try. I thought about glue failing,.. was actually considering gluing acrylic. Weld On glued acrylic becomes like one solid piece, extremely reliable, sets in 2 minutes, strong enough in 10. Also I was thinking of making back to back mark IV like trays. No matter how you spin it that requires at least some joining anyway. Really I should borrow a shop key at night and just mill it from a solid block.

Of course you can buy these now, but what fun is that? I can make a nice one-piece 8 pack if I do it myslef. 

How much compression do you allow for the springs?


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## kocoman (Aug 22, 2013)

does anyone have a fix for the pics not loading? thx


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