Tubular 18650 solderless pack

Nice. Very stealth system!

P.S.There are 3.5Ah cells already available for cheap, considering I only get~1.2Ah out of my old konions its almost 3x improvement waiting to happen. :D
 
Thanks for commenting. In the voltage range I use I also get 1.2Ahr per Konion cell. For this bike it's enough. Today it was 31F out and I rode 19 miles, I pedalled hard to keep warm. That's about as far as I intend to go with this bike so I am happy with these cells for this application.

I like the stealth/simlicity, no load speed is only 17 mph,it only has a rear coaster brake. The 3-speed hub is geared just right for 17 mph in high gear. It has a thumb throttle with no PAS. For the cold weather its fast enough for me. I like PAS on my other bike, but for this bike I tend to be at wide open or no assist.
 
I certainly like the idea of no solder/weld packs.

I'm an E-bike newb, waiting for my new Stunner, but already thinking about a "spare" battery. And thinking of building it myself. the first question that came to my mind was could I series together in a flashlight manner. Which led me to this thread.

Thanks for answering my question. I believe I came across the figure 9 pounds of force is enough.

Keep in mind I'm new, another question is; since the pack would easily be disassembled in winter (or more often) how necessary is balancing wires, assuming you start with new, and equal cells ?

My design is coming along nicely in my head, so long as it don't get crushed.
 
rick (nova scotia) said:
I certainly like the idea of no solder/weld packs.

I'm an E-bike newb, waiting for my new Stunner, but already thinking about a "spare" battery. And thinking of building it myself. the first question that came to my mind was could I series together in a flashlight manner. Which led me to this thread.

Thanks for answering my question. I believe I came across the figure 9 pounds of force is enough.

Keep in mind I'm new, another question is; since the pack would easily be disassembled in winter (or more often) how necessary is balancing wires, assuming you start with new, and equal cells ?

My design is coming along nicely in my head, so long as it don't get crushed.
Click to expand...
You certainly need balance wires, not for balancing itself but for supervision. It leads to another questions answer, you can arrange your series in flashlight style if you figure how to make balance connections. Cells will generally stay balanced if they are new and used in not abusive manner but if 1 cell is defective in some way then your pack is a ticking bomb and you should know it before avalanche happens.
 
I agree with the post above, you need to have a method to know that the groups are in balance as well as confidence that all cells are good. An advantage of these type of assemblies is that they can be disassembled and each cell checked or tested.

Spring tension is dependent on many factors, I am using 8 to 10 pounds and it's been working well for me. I have about 200 miles on this pack and happy with it's performance. This is a lot more spring force than a typical flashlight.
.
Here are some factors to consider
1--how much current are you pulling--I have a low power setup and seldom draw more than 10 amps. I charge at 3.5 amps.
2--how much actual surface area do contact points provide. I use brass nuts as contacts and depending on fit the contact area could be the area of the nut or just a point contact. Some guys have formed bumps into the copper plates, this may be a better technique if the bumps are slightly flexible and provide more contact.
3--how well are the cells contained to prevent side to side movement. High spring force can help keep every thing tight

A gallon of water weighs about 7.5 pounds, just to think about to help get a feel that this is fairly high force.
 
IdleMind said:
I agree with the post above, you need to have a method to know that the groups are in balance as well as confidence that all cells are good. An advantage of these type of assemblies is that they can be disassembled and each cell checked or tested.

Spring tension is dependent on many factors, I am using 8 to 10 pounds and it's been working well for me. I have about 200 miles on this pack and happy with it's performance. This is a lot more spring force than a typical flashlight.
.
Here are some factors to consider
1--how much current are you pulling--I have a low power setup and seldom draw more than 10 amps. I charge at 3.5 amps.
2--how much actual surface area do contact points provide. I use brass nuts as contacts and depending on fit the contact area could be the area of the nut or just a point contact. Some guys have formed bumps into the copper plates, this may be a better technique if the bumps are slightly flexible and provide more contact.
3--how well are the cells contained to prevent side to side movement. High spring force can help keep every thing tight

A gallon of water weighs about 7.5 pounds, just to think about to help get a feel that this is fairly high force.
Click to expand...

THANKS VERY much Idlemind.

1) I agree with you, that because it is easy, and pretty quick to take apart you can check individual cells often.

I understand about the flashlight's low spring pressure,...and the low draw of a light bulb.

I don't intend to spin my wheels, so a modest 10 AMPS max.15 AMPS

I understand that a dimple contact point won't conduct as much as a larger surface. One thought is use small thin rare earth magnets between ends if the metal parts of the batteries don't touch, or get the type that have the raised button + end.

The pack will be the equivalent of a 10s6p, 60 cells, but the way I'm thinking to assemble it will be really only be one big parallel group. I don't have any fancy drawing software, but maybe I could put up a simple "sketch" of my layout.

Thanks, again.

PS any "hobby" I've ever got into, I went all the way.
 
Jonathan in Hiram said:
Great idea, I love it.. A couple of modifications come to mind due to what I already have on hand. Pure copper foil tape with conductive adhesive, two layers put sticky side toward each other with brass or copper washers in between the layers to make the bumps.

Neo disc magnets for the spring compression on one end of your cell stack, copper foil tape again with magnets sandwiched between the adhesive layers and other magnets arranged in the end cover to compress the stack. I'm only thinking this because I have a couple of hundred of them right now. :)

I had a different kind of build planned but I like your idea enough to give it a try I think.
Click to expand...


I like the copper tape idea a lot too and plan to use it with a compression pack but am worried I won't have a good connection.
How much resistance would be ok between cells? I doubt my multimeter will show the small resistance or a voltage drop...is there a way to test how good connections are?

how thick will it need to be for a 12 amps max? Sticking two pieces of tape together sounds ideal, and then banging a flat divot

I imagine it wouldn't need much compression. Maybe 2lbs on a 1/4 spot.
 
If you give this a try, here are some things to think about.
1--be prepared to spend a lot of time because it's harder than it looks
2--if you do it right it can work really well
3--the springs I use are compressed to 8 to 10 pounds
4--the copper plates are .008 inch thick
A group of parallel cells will have length tolerances especially if all cells not the same. With 8 pounds of spring force the thin plates can flex to allow for length tolerances
5--however you make bumps on the copper plates, they need to be located accurately enough and small enough that they can only contact the anode. I don't use bumps on the cathode end of the cells
6--In the most recent pack I made I changed from using 6-32 brass nuts as contact bumps to smaller 2-56 brass nuts to allow for more tolerance on there location
7--Other guys have shown ways to form bumps in the copper plate which I think may be a better method depending on your abilities and tools.
8--I recently made a 10s12p version for a cargo bike I am building--it can get kinda scary assembling that many cells with 12 plate dangling on a balance harness knowing a slip can cause massive sparks. So think about how you will assemble the pack.
9--the cells have to be retained laterally in the housing so they can not move out of position or wiggle around. But not so tight that the spring can't push them axially to maintain contact force
 
Thanks. I hope to simply make a very tight fitting battery holder without any springs and just relying on the constriction of the holder material

I got this copper:
http://basiccopper.com/10milcost1x1.html

Bit thicker than yours I think

I plan to give it a bump with a hammer using a washer's center recess to bang it into a bit

It's 1" wide and planned to cut it to 1/2"
 
This thread is one example of why images ought to be attached to the posts, so they are preserved with teh thread, rather than hosted on external sites that go away or change their operation, rendering such threads pointless without their images. :/
 
Yep, would like to have seen some photos of this 😐
 
We really appreciate that! :)

I wish there was some way to make it more obvious that pictures can be attached, because the picture icon in the posting box only does links of them, and thats all most people ever see. If clicking the icon the first time when posting would have a text box to tell you to please try using the attachments tab below to upload instead, and then allow you to just link if you prefer to, it would help those that dont know yet.


Unfortunately there are people that *wont* upload images to ES, and instead insist on using external sites, so either data gets lost (when the sites go away or change) or cant even be seen at all by some viewers (sometimes all of them except the poster, as they dont understand how to link them or their site is private, etc). So there are a lot of threads that are totally useless because they depend on the images to convey the essential information.
 
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