connections without DIY welding / soldering

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john61ct

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Dec 18, 2018
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Looking for examples of connection methods when DIY bank assembling,

that do not involve directly applying heat to the batteries themselves.

Here is one example to start:
https://www.ebay.com/itm/Brand-New-6-A123-3-2V-18650-1100mAh-Lifepo4-Rechargeable-Battery-30A-w-Tab/303075753365

Personally only interested in LFP, but welcome examples using other chemistries - if possible please state the specific chemistry of other examples.

Battery holder examples are most welcome, DIY designs or OTS products, or a mix, whatever,

but must be secure in a mobile context, both due to high vibration/shock, and potentially high current rates.
 
This looks promising, but IMO overly expensive cost per cell.

https://danlimblog.blogspot.com/2018/10/p1-416-open-frame-power-pack-kit-its.html?zx=90926629d59c6d3

Note I want to easily monitor - test at the per-cell level, and relatively easily replace individual EoL or under-performing cells as a regular maintenance procedure.

From this "crowdfunding" thread

https://endless-sphere.com/forums/viewtopic.php?t=99012
 
YOu might want to read around the forums; there are a lot of existing threads for such things.

One example search for no-weld solutions (no-weld isn't findable due to the "no-" but weld is, so easy to look at the titles....)
https://endless-sphere.com/forums/search.php?keywords=weld&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

A similar search for "solder" would find some of the no-solder threads.
 
Thanks, will try those search strings, and use this for my scratch notes as I learn more.

Hopefully people will contribute comments on the very good, or very stupid ideas :cool:

Came across these as better than the spring holders, designed for 18650, can Dremel a bit for the bigger diameter, same length A123s
https://www.amazon.com/Battery-Holder-1-Slot-Storage-Connector/dp/B07D1FRL54

Look good for temporary testing, could perhaps be part of a more robust DIY system for production use.
 
From this thread https://endless-sphere.com/forums/viewtopic.php?p=1453626#p1453626

don't want to derail that one so much, sorry

spinningmagnets said:
If the contacts are also made from a very stiff material, microscopic irregularities means that there will be more pressure applied in one area, and less in another
Click to expand...
Very well clarified, thanks again.

OK another tack. Forget physically holding the batts for now, just focus on the electrical contact functionality.

A layer of compressible rubber or relatively dense foam between the batt ends and opposing "clamping rails" maybe say aluminium U-channel.

A small die-cut patch of:
3M ECG7000H series electrically conductive compressible cushioned tape*

holds the fine tinned strands of a fanned-out marine-grade wire

51155039ce395f2754000001.JPG

between the battery end and the cushioned surface at each end.

Those two opposing "clamping rails" are tightened toward each other in a controlled manner, like a precise torque wrench.

____
* This one
https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Electrically-Conductive-Cushioning-Gasket-Tape-ECG7073H/?N=5002385+3294001372

is 28.3 mils / 0.720mm thick, comes in 4" x 10' rolls

excellent gap filling performance

conductivity through the thickness (Z-axis) & in the plane of the adhesive (X-Y planes)
 
spinningmagnets said:
zzoing wrote: thanks to the genius discussions on this forum in about 2014

Anyone know what threads being referenced here?
Click to expand...

No Solder / No Weld

"Another No Solder/Weld 18650 Build" (snath, 6 pages [plus more links to other no-solder/no-weld builds])
https://endless-sphere.com/forums/viewtopic.php?f=14&t=57810

"18650 battery Kit development and discussion" (agniusm, Another no-solder loose-cell box, 7 pages)
https://endless-sphere.com/forums/viewtopic.php?f=14&t=63190&start=125#p1238901

"Conductivity improving grease project" (liveforphysics, 5 pages)
https://endless-sphere.com/forums/viewtopic.php?f=14&t=61542

"Modular Rebuildable Repairable 18650 battery." (shawname "Battery Blocks", using magnets to make connection at cell-tips, instead of spot-welding)
https://endless-sphere.com/forums/viewtopic.php?f=31&t=76205

"DIY assembly kit for 18650 without spot welding/Soldering" (Vruzend kit)
https://endless-sphere.com/forums/viewtopic.php?f=31&t=87434

"yet another solderless DIY battery pack via NIB's" [also using button magnets to hold busses onto cell ends]
https://endless-sphere.com/forums/viewtopic.php?f=14&t=60517#p917007

"Electric Motorcycle (50cc Equivalant)" [19P modules for 14S]
https://endless-sphere.com/forums/viewtopic.php?f=10&t=85758
Click to expand...
 
I don't think the splayed strands connection will gain much popularity, but I like it! The foam "spring" of choice for a while has been a disc of Poron.

The conductive glue on that 3M product probably has relatively poor conductivity (I'm guessing), but...so does solder. I wouldn't use it as a link in the conductor chain, but to hold down some strands might work OK.

I think there are plenty of existing methods that work fine for low amps, so any research and experimentation I do is focused on higher amps.
 
Thanks, very encouraging!

By "low amps" do you mean absolutely or C-rate?

Say a 800Ah bank feeding say 40-60A maximum continuous at any given time.

Of course using these tiny 3A cells in that context, the amp rate (and C-rate) per cell-wire would be pretty low.
 
spinningmagnets said:
"spring" of choice for a while has been a disc of Poron.
Click to expand...

Noted for research, along with
spinningmagnets said:
Cembre ring connectors are zinc-plated copper, and the copper is annealed to make it as soft and deformable as possible. The first time you tighten it down to a contact, the copper "flows" slightly and conforms to the shape of the contact point (as it is squeezed between the nut and the electrical contact) But after doing that several times, the copper "work-hardens" and becomes brittle.
Click to expand...
from the original thread



 
The connection between a wire and the cell tip (electrode) will be the same whether it is a high C-rate cell or a low C-rate cell, so I am referring to the absolute amps.

Drawing high amps from a low C-rate cell will get the cell hot, but if the connection between the cell and bus is capable of high amps, at least the connection will not get hot.

Most of the materials we are talking about become more resistant when they get hot, so rather than the heat being stable, it will get hotter when it gets hot.
 
Thanks, this is during the pilot run stages, will be better once the quantity goes up. Do check out the latest update on the 416 OFPPK fb group.

john61ct said:
This looks promising, but IMO overly expensive cost per cell.

https://danlimblog.blogspot.com/2018/10/p1-416-open-frame-power-pack-kit-its.html?zx=90926629d59c6d3

Note I want to easily monitor - test at the per-cell level, and relatively easily replace individual EoL or under-performing cells as a regular maintenance procedure.

From this "crowdfunding" thread

https://endless-sphere.com/forums/viewtopic.php?t=99012
Click to expand...
 
I assume the cylinder sides are never "live", including right down past the "shoulder", so adding per-cell heat shrink wrap is not needed? man that stuff gets crazy expensive! at least from 3M

For 26650 cells

What is the diameter spec for the conductive area at the center of the round ends?

Same for positive and negative?
 
Also, does anyone know of insulating "cup" end caps that would have enough stretch to accommodate say a 16 AWG wire "turning the corner" under there?

And finally, what would be a good adhesive for fixing the cable-pair insulating jacket to the cell wall for strain relief? don't want any pulling on the cable to transfer to the individual wires' connections.

Thanks in advance!
 
john61ct said:
I assume the cylinder sides are never "live", including right down past the "shoulder", so adding per-cell heat shrink wrap is not needed?
Click to expand...
Not sure what you mean?

If you mean the cell can itself, the entire can is always live, it's all the negative end of most cells (I think there was a cell out there that had positive can, but can't remember what it was...not a common one, not an 18650 or 26650--but anyway it also had live can).

This is why fires (or at least pack damage/destruction) occur to some packs that are just taped/glued together, rather than using spacers, because if the cells come unsecured from each other (or the heatshrink cracks or breaks down) they then can rub during vibration, further rubbing the cells together, until at least one cell in each of alternating rows touches each other, shorting across one of those entire groups, either completely or intermittently. :(
 
Yes, that is what I meant, and wow. But something that common I guess can't call it stupid then. 8-(

So then, from the center of the positive end of a 26650, how big is the live + area?

And please don't tell me it can extend right up to the shoulders edge. . .

 
And suggestions on robust but reasonably priced shrinkwrap, maybe even on

the endcaps Q would be greatly appreciated.

Also now I guess I need to also look at spacers, OTS ready-made as opposed to re-inventing the wheel?
 
john61ct said:
Also, does anyone know of insulating "cup" end caps that would have enough stretch to accommodate say a 16 AWG wire "turning the corner" under there?

Poke around here https://www.mscdirect.com/browse/lookahead/?searchterm=stretchable+cap&hdrsrh=true. Is that the right idea?

From this supplier these appear to jump from 5/8" (.625") to 3/4" (.750"), whereas 18mm as in 18650 is .709", so if you could source an 11/16" size it might be a better fit. But they are pretty stretchy, I think the 5/8" size would be fine. Prices are per 100. MSC is a great source for materials and widgets.
Click to expand...
 
Sorry if I wasn't clear enough, only interested in 26650, so 1" and a smidge diameter.

Looks like 1/3-1/2" is about right for the conductive adhesive + conductive tape diecuts to stick the splayed strands to the ends.

I'm thinking a 1" 3M electric tape cap, then a blob of 3M 4200 as a flexible convex dome to maintain pressure on the ends, clamped towards each other within a thermally conductive strong dielectric-potting, all lined up in an epoxied Plasti-Dipped aluminum box.

Case'll cost as much as the cells :cool:
 
kansas said:
Poke around here https://www.mscdirect.com/browse/lookahead/?searchterm=stretchable+cap&hdrsrh=true. Is that the right idea?
Click to expand...
Beautiful! plenty of choices and the price is rightt!

Thanks

 
I believe many here consider it an unsafe design for handling shock / vibration?

Links to threads with solid info would be appreciated.

Plus this thread is wrt 26650 cells, looks like those are for 18650 only?
 
https://endless-sphere.com/forums/viewtopic.php?p=1461306#p1461306

An example of a setup where being able to dis- / re-assemble a bank would really make troubleshooting and repair easier.
 
Search string

https://www.google.com/search?q=site%3Aendless-sphere.com+weldless+OR+solderless

Also batteryblocs.com, have asked for commentaries not much feedback so far.
 
Agnuism
https://endless-sphere.com/forums/viewtopic.php?t=100093

also https://endless-sphere.com/forums/viewtopic.php?t=88051
 
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