# Yet another 18650 battery holder :)



## El34 (Jan 11, 2009)

I have been getting request for 18650 battery holders and so I cut a 4x18650 prototype on my CNC machine today.

This one is cut from High Density polyethylene (HDPE).
The same meterial I cut the DX to Marwi adapters from.





































These are the battery terminals I am going to use.



















These are some of the possible shapes for 2,3 and 4 18650 battery combinations.










I don't have the battery terminals yet and so I have not worked out how they will mount, but they already have small holes for tiny screws. They look to be very high quality. Much nicer than the thin tin type battery terminals.
The termianls could be set up for any configuration like parallel, series or series parallel.
they have small solder tabs on them which may work out nice.

The threaded rod and nut is Nylon, which is really tough material.
The whole thing weighs in at 28grams. 

I have much larger pictures and more info here.
https://www.el34world.com/Misc/bike/BatteryHolder1.htm

I am looking for feedback on this design.
I am going on vacation in a couple weeks, so I don't know if these will be available before then.

Thanks for any input and ideas for improving the design.


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## [email protected] (Mar 28, 2007)

El34

This is a brilliant idea. You probably don't need a CNC mill to make one of these. Though a drill press will make it easier.

A 3/4 inch wood drill bit like this: http://www.mcmaster.com/#2894a56/=35abav is probably close enuff to the diameter of an 18650.

If you use 1 inch thick Polypropylene sheet:
http://www.mcmaster.com/#8782k37/=35bdxq

and something like:
http://www.mcmaster.com/#93665a635/=35bf4l

for the threaded rod, you could almost build one of these with a hand-drill.

The nuts will be easy to find, and battery fittings are available from digikey (with a bit of searching, they are made by keystone).

Thanks for sharing this idea. I've been kind of down on the idea of using Li-Ion batteries due to their tendency to spontaneously explode, but this may make me look at using them in a few designs.

Mark


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## Vancbiker (May 25, 2005)

Those are the same terminals I use on my 18650 holder. This thread describes how I mounted them....

http://forums.mtbr.com/showthread.php?t=501179

They are high quality and the spring is pretty strong. I have not had any instance of the batteries "bouncing" and losing contact. I use a piece of innertube to as a band to hold the batteries in.


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## El34 (Jan 11, 2009)

Thanks for the input guys.



> You probably don't need a CNC mill to make one of these


I use the CNC machine because I lay down a big sheet of HPDE and cut out 50 at a time while drinking a beer. 

No user intervention or labor required once you dial in the CNC machine code.
Well actualy, I have to run the tap on a screw gun which takes about 15 seconds.
The only way I can actually sell this kind of stuff is to keep my labor to a minimum, which is what the CNC machine lets me do. (After the design and CNC steup is done that is, which sometimes takes quite a while)

Vanc, that's great to hear on those battery terminals.
I don't have them yet and was hoping they worked as good as they look in the pictures.
They should be here by friday.
I like your 5 x 18650 holder.

I think the 4 x 18650 design I show above will probably be what most people want?
I could use some feedback on what you guys like to use
2 x 18650, 3 x 18650, 4 x 18650, etc?
thanks again


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## ndrordr (Dec 11, 2008)

Might I suggest an improvement. It would be easier on the user to remove and replace batteries (for charging individually) if you replace the hex nut with a nice wing nut.

Just a thought.

Rob


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## El34 (Jan 11, 2009)

good idea.
I thought of countersinking/recessing the nut also so it does not stick out as far.


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## mojojojoaf (Sep 9, 2008)

4 cell and 6 cell holders get my vote- but I am slow and need lots of power to get me through a ride.


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## El34 (Jan 11, 2009)

A 6 pack huh?

Alright, thanks for the input.

Hard to tell what folks want without feedback.


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## mcdooo (Aug 13, 2009)

El34 said:


> good idea.
> I thought of countersinking/recessing the nut also so it does not stick out as far.


good idea sir


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## mojojojoaf (Sep 9, 2008)

I thought everyone likes 6 packs (of root beer) LOL


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## sdnative (Aug 10, 2008)

El34 said:


> A 6 pack huh?
> 
> Alright, thanks for the input.
> 
> Hard to tell what folks want without feedback.


Go big or go home baby !!

I'm working on an 8 cell actually. Not sure everyone needs one, but I do


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## odtexas (Oct 2, 2008)

Love these DIY holders. May eventually make me give up the pre-made battery packs.
SDN....... Fit and finish on your holder is great. Also cool that you are entertaining CR123 requests.
El34.... Simplicity of design and simple assembly. Removing a little material between cell holders would allow for easy parallel wiring. Also I think El34's holder would work with the CR123s as is by just running a short bolt and leaving a whole bunch hanging out the end.


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## El34 (Jan 11, 2009)

6 packs are my favorite.  But I use 4 cells.

OD,
I was waiting on the + and - minus terminals to arrive and then I can map out how the center sections will be trimmed so they can all be joined in series or a parallel connection. 

Still thinking about the wire routing and how it exits the holder.
No solder joints right on the end of the pack that can break off easily
I want good strain relief as the wires exit the holder.

It's gonna take me a bit to figure it all out.
leaving on vacation in a couple weeks which will set things back a week or so.


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## El34 (Jan 11, 2009)

Ok, I had some time to cut a 2nd design 18650 battery holder on the CNC today.

The Major differences are that I now have the + and - battery terminals, and so I was able to formulate a plan as to how they would integrate into the battery holder.

I am going to cut a 1/32" copper circuit board that the battery terminals will be soldered to. The circuit board will drop down into each of the end pieces.
You can have series/parallel configurations or parallel, depending on the circuit board configuration

The nut that secures the whole thing together will be a large diameter nut that you can easily grab with your bare hand or gloves and screw the whole assembly together.

The thickness of the nut shown is about 2X the actual thickness it needs to be.

I have to run now, more pics later.|
design 1 is at the top of the photo
design 2 is at the bottom of the photo


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## odtexas (Oct 2, 2008)

Man you have huge nuts.....


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## El34 (Jan 11, 2009)

I thought Texas had the biggest nuts?
LOL

The big nut offers a larger turning surface and a much larger diameter to grab a holt of.


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## thysmeades (Jun 24, 2009)

Nice one Doug!! now we just need prices!


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## El34 (Jan 11, 2009)

I have some more ptototyping to do first.
Gotta cut some small circuit boards that the battery terminals mount on to.

I still don't have a clear idea of how the wiring is gonna hook up or how it will exit the body


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## thysmeades (Jun 24, 2009)

hi Doug, my advice is keep it simple. rather let the user wire it up in series or parallel with a little soldering. I doubt if someone needs a pack in series and then later will need the same pack in parallel. it would be, one or the other, set up once with a little soldering and then that's that. If they need one is series and parallel, then they should order two!! 

Anyways, that's just my advice, but there will probably be a post just below this one saying that they want it in parallel and series!!

Just try keep the cost down to get the numbers out the door.

regards
Thys


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## El34 (Jan 11, 2009)

yeah, I agree.

I don't plan on assembling them.
It would be a kit that you can assemble into whatever configuration you want.
The main body, the battery terminals, maybe some wire.
better off letting people hook up whatever type of wire and connector they like to use.

I imaging just a rough cost at this point on the 4x18650 to be under $15 for the body, battery terminals.
Could be less.
Don't know till I see how much time it takes up on the CNC machine.
I generally charge about $1.00 per minute of CNC cutting time on parts.


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## El34 (Jan 11, 2009)

Ok, I made some more progress today.
I cut out some cool copper circuit boards that the battery terminals get soldered to.
The boards then drop down inside the ends.
They could be glued in place, but the ones I did below fit really snug.

Larger photo's and more info here.
https://www.el34world.com/Misc/bike/BatteryHolder1.htm


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## mojojojoaf (Sep 9, 2008)

These look great- Look forward to seeing the finish product.


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## El34 (Jan 11, 2009)

Thanks Mojo,
I still have not worked out the wiring details.

I had several request to sell the battery terminals and so I added both of them to my web store here.
http://www.hoffmanamps.com/MyStore/catalog/PartsLed.htm


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## mojojojoaf (Sep 9, 2008)

By the way the one on your website showing the 4x inline flat-pack design looks good too. Nice one for the inside of my camelback pocket.


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## El34 (Jan 11, 2009)

yeah, I like flat packs for jersey pockets and outside mesh compartments.

I sent you a PM.

I just cut the third prototype with holes for routing the battery wires.
I'll post pics tommorow.


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## seeker (Feb 15, 2004)

great

you should consider packaging the entire P7 parts kit and battery together

price?


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## HuffyPuffy (Jun 9, 2008)

That holder looks great. It looks like it will be very tough, and the new nut looks much more functional - and it's a great place for a logo. Is there enough wiggle room around the cells in case they get damaged and vent? 

The cable routing for the parallel wired holders looks like it will be a challenge, how are you planning to do it? Will it have a pigtail or connector?


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## El34 (Jan 11, 2009)

yeah, the parallel packs are the ones that are giving me grief.
It means that the + and the - wires have to leave the battery holder at opposite ends.
The battery holder dismantles so that you can insert the batteries.
This means that the two battery ends are still connected by a split zip wire.
I guess it's not that big of a deal, it just bugs me.

A series or series/parallel pack is much easier. Both wires would leave from the same end of the battery holder.

I'll post pics tommortow, just getting home from a ride

see ya


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## El34 (Jan 11, 2009)

I have settled on a design for these 4x18650 battery holders.
It could change later, but they are pretty nice as they are.
I have added some small holes in each end cap that allows you to pass wires through.










It's hard to see in this small picture. You can see way more detail on my "how to assemble" page here.
https://www.el34world.com/Misc/bike/BatteryHolder2.htm

Here's a shot of one that has the wire routed out the end cap.







https://www.el34world.com/Misc/bike/images/IMG_1617_small.jpg

They take way more time to cut on the CNC than I thought they would.
It looks like about $16 for a kit with all the parts showing in the picture at the top of my post here.
I am going to cut some of these out and then add them to my web catalog.
I'll post back when they are ready.

Check out the assembly page link above for way larger pics and more info


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## thysmeades (Jun 24, 2009)

Hi doug, nice! what about arrangement in series?
T


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## El34 (Jan 11, 2009)

Yes, working on that.
All I have to do is cut circuit boards that only span two battery ends.
The parallel boards span all four battery ends

I should have those ready in a couple days.

By the way, these will be a kit of parts that you have to assemble.
Just in case I gave the impression from the pictures that these will be a all soldered together.


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## El34 (Jan 11, 2009)

Here ya go Thys

Just finished cutting a stack of Series/Series/Paralell boards.

You would use four of the boards shown on the right below for Series or Series/Parallel wiring.

Gonna be a couple more days before I am ready to put these on the web store.

more info and bigger pics here
https://www.el34world.com/Misc/bike/BatteryHolder2.htm


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## Trub (Aug 21, 2009)

Hi Doug,

I've been reading a lot of your posts and would like to buy the Marwi SSC P7 conversion kit, Marwi handle bar mount and a battery kit. The battery packs I've seen come in a small nylon bag that Velcros on to the top tube. Where would I get one of those, or is there another way to mount? I prefer to have it attached to the under side of my top tube and be encased in something for protection.

Great job, BTW...


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## El34 (Jan 11, 2009)

I don't have a source for those bags..........yet. 

I tried to talk my girlfriend into sewing up a couple prototypes but she wants to see one in person first.

I may show her the DX bag and then have her create one nicer than that.

Not gonna be anytime soon, we are getting ready to go to Utah for a vacation and I have a bunch of stuff to do before then.

I actually use a really cool go-gel flask bag I got years ago somwhere.
A 4x18650 pack fits perfectly in it and it slings under the top tube.
Maybe I'll show her that one and see what she thinks.


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## Vancbiker (May 25, 2005)

Trub said:


> Hi Doug,
> 
> The battery packs I've seen come in a small nylon bag that Velcros on to the top tube. Where would I get one of those, or is there another way to mount? I prefer to have it attached to the under side of my top tube and be encased in something for protection.
> 
> Great job, BTW...


I use a case for a small digital camera to hold my battery holder. Got it at a local "variety store" for about $8.


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## El34 (Jan 11, 2009)

I noticed when I was at Walmart the other day they had at least 30+ different small camera bags.


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## El34 (Jan 11, 2009)

Came up with another mod idea for my basic 4x18650 battery holder.

What if both the battery holder end pieces each had a half pipe shape that fit right onto the top tube?

I measured 3 of my bikes and all the top tubes were right around 1.25" in diameter.

You could glue on a small piece of inner tube rubber to keep from scratching your frame and to keep the battery holder from moving around.

I supposed two long pieces of velcro could be tacked onto each battery body end

These vecro pieces could just wrap around the top tube and attach back to themselves?

Each battery holder end piece could have a shape like this










Just throwing out ideas.


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## mojojojoaf (Sep 9, 2008)

I wouldnt mind a hard case similiar to above that had at least a concave surface to better fit my stem. Throwing it back at you.


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## El34 (Jan 11, 2009)

You mean like a solid case that all the batteries fit inside of?


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## kcalvano (Feb 14, 2007)

I think a solid case would be ideal, IMHO. That way you would have the option of mounting it to the tube as is, or tossing it in a pouch. With your design, maybe a sleeve that fits around the outside perimeter of the batteries and sandwiched in between/on the inside of the end caps.

Just an idea, of course the end caps would be closed, just showing for illustrative purposes,









Great design btw.


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## El34 (Jan 11, 2009)

I can't really make a tall hollow container like a can.

The sheets of material are only so thick.

A CNC endmill can only reach so deep.
 
Even if you could mill material really deep like that, a solid block of material that deep would be really expensive.

That's probably a job for some sort of injection mold machine?

I use 1/2 thick HDPE sheets to make those end caps.

I am cutting some in the shop right now.
As it stands, each battery holder takes 16 mintues to cut on the CNC.
That's way too much time, but there are so many cuts to be made and the shaping of all those cavities takes quite a while.

But, they are really nice!


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## kcalvano (Feb 14, 2007)

A thin mil semi-rigid plastic/metal to give it a bit of protection. That's kind of what I was thinking anyway.
More along these lines:


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## HuffyPuffy (Jun 9, 2008)

How about just adding some tabs to run velcro tape though since some bikes have a different profile? If you want to enclose the pack, one cheapy way would be the thick rubberized heat shrink, though that would make the pack pretty well permanently assembled. Another option would be to form a square tube from Kydex which can be heated and molded into shape around a form, then add a groove to the top and bottom plates to hold the kydex insert in place. When I checked I found several sites with mini-tutorials on molding kydex for holsters. I would guess that the best way though is the simplest, that is the original design, and use a small bag which attaches to the frame with some velcro straps.


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## El34 (Jan 11, 2009)

Yeah, a Velco bag is the simplest solution.

I was thinking that neoprene/wet suit type material would make a good bag.

My Lume HID came with some really cool rubber mounts that went around the battery pack and then had a profile like the top tube.
You velcro'd the whole pack to the top tube.
The rubber mounts kept the pack from wiggling.

I was just thinking that it would be cool to do something like that.
I'll have to run off a prototype and give it a test later on.

But first, I have to finish cutting a bunch of the regular 4 x 18650 battery holders.
I should be able to put them on the web store tomorrow.

I made another mod to the end caps, I now have two exit holes on each cap.
This lets you route the battery wire back out one of the holes and gives you more strain relief.


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## HuffyPuffy (Jun 9, 2008)

That mod looks great, should give it much more strength and best of all, it is still simple.


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## El34 (Jan 11, 2009)

Thanks Huffy,
I could actually do 4 holes in each end piece, for even more wire routing flexibility.
I may do that, it's real easy and does not take up much cutting time on the CNC.

I have enough of them cut now.
I will be closed for most of next week and so I wanted to get some done for those that can't wait till I get back from vacation.

I'll add them to the web store in the morning and announce it here when they are ready to go.

see ya


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## Trub (Aug 21, 2009)

I just placed an order for the Marwi P7 conversion kit before reading this. I'd like to add the battery pack and 4 18650 to that order. Let me know what I need to do, if anything.

Thanks,
Chris


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## El34 (Jan 11, 2009)

Sorry, didn't see your post here Chris.

Your order is already gone and on the way.
I am getting ready to add the battery holders to the web site.

If you still want some more goodies, just place another order later today and I'll get that one out ASAP also.


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## Trub (Aug 21, 2009)

El34 said:


> Sorry, didn't see your post here Chris.
> Your order is already gone and on the way.


Dude that was crazy fast! I'll order them once I see them.

Thanks


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## El34 (Jan 11, 2009)

> Dude that was crazy fast!


yeah man, that's what I am known for.

I have so many orders in the morning when I get to the shop, I have to get them all shipped out the same day.

I didn't see your post here until after I had finished packing all the morning orders up.

Postman gets here very early sometimes and so I have to haul arse.


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## El34 (Jan 11, 2009)

Ok, I just added the Battery holders to my web store.

There is a Parallel kit and a Series/Parallel kit.
The only difference between the two kits is the copper boards.

I am going to go place a MTBR classified for these items in just a bit.

Here's the web store page where the kits can be found
https://www.hoffmanamps.com/MyStore/catalog/PartsLed.htm

Note that I am leaving on vacation in just a few days, so if you are in a hurry, git-r-done soon as you can. When I get back back from vacation, it will be crazy busy here and things will be delayed. Best to order now if possible.

Thanks all
Doug


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## mojojojoaf (Sep 9, 2008)

I got the 4 cell holder todayand thats pretty cool. I like it. Crap my last order I forgot to get Anderson Pole connectors.... doh! Iwill put an order in later this week.

The newer designs look great as well... looking forward to seeing how this evolves.


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## El34 (Jan 11, 2009)

Oh yeah, I forgot, you got one of the prototypes.

Hope it works out for you.
Let us know if you come up with any cool mods.

You can drill wires holes, just like the current design.
That HDPE machines like butter.

I like to dial things in based on user feedback
see ya


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## Joshp82 (Apr 1, 2009)

Are you still making these holders? I need 2 of them yesterday.


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## El34 (Jan 11, 2009)

Hi,
No, I am not making these.
Too much work, not enough interest, etc.

There's a few others here that make battery holders.


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