Index of flat pouch cell connection methods

spinningmagnets

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There doesn't seem to be a definitive DIY solution to connecting the tabs on pouch cells, but quite a few ideas. I come across variations when I read about a pack build, so I'd like to collect the types here as a reference and a place of discussion.

Today I just found out about the "Termifoil" connector. I believe its zinc-plated copper.

53264-2.JPG


ES member flexy mentioned a proposal using copper flat bar with "through bolts" and a paper hole puncher.

https://endless-sphere.com/forums/viewtopic.php?f=10&t=38617&start=75#p762822

tab%2520clamping%2520plates.jpg


Then, ended up using vertical screws that attach a copper top-plate to aluminum square-bars underneath. The aluminum bar is drilled and tapped with threads (the threaded "underbars" could be steel, since the copper does the conducting). The tabs insert from underneath through slots in a non-conductive plate made from the same material as PCB boards, and then the tabs are folded over 90-degrees and compressed between the copper and aluminum.

Th sub-pack shown is 6S with 5P bundles

20130526-IMG_20130526_174715.jpg


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The aluminum bars above are theeaded, and they could be steel if needed.

Jonescg has done something similar. This pack is 5P bundles, and the cells are arranged in a long "U" shape so the positive and negative terminals are at the same end of a rectangular pack. 12S shown, terminals are at the top of the pic.
https://endless-sphere.com/forums/viewtopic.php?f=31&t=38252&start=425#p1280164

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Zappy used a common method of having the tabs touch each other with nothing in-between them, then he folded a thick copper sheet section over the tabs and used three bolts and nuts to clamp the assembly. I'll look for a better pic, but here is an example:

https://endless-sphere.com/forums/viewtopic.php?f=14&t=38761&p=670305#p670305

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Here's a pic from "pullin-gs", tabs are located on opposite ends of each pouch-cell, which allows each tab to be a much larger tab. Since the tabs are touching skin-to-skin, the compression connector-plates can be steel for added strength, which allows them to be thin, but still rigid.
https://endless-sphere.com/forums/viewtopic.php?t=98770#p1446391

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Here is a terminal connection by Doctor Bass

https://endless-sphere.com/forums/viewtopic.php?f=14&t=38761&start=600#p709069

file.php
 
the problem with pouch cells connecting is that cathode aluminium tabs oxidizing really fast after cutting/sanding which in my book increase connection resistance.
how much those oxidizing alu tabs add to internal resistance of my pack?
that is why I want to add some soldering to my assembled with brass screws Chevy Volt 11S pack.
 
I ride everyday in nice weather here
to do such spot soldering I would have to take my pack apart and it means sacrificing 2 days of riding.
how I am planning to do it?
tabs on pouches are screwed together with aluminum brackets with brass 8-32 screws and nuts.
I am going to cut 1cm of corner across tabs , and immediately after apply aluminum soldering flux and solder.
so solder 1cm long.
I am really curious how it is going to lower resistance of pack?
 
miro13car said:
the problem with pouch cells connecting is that cathode aluminium tabs oxidizing really fast after cutting/sanding which in my book increase connection resistance.


The Chevrolet Volt cells DO NOT take to soldering very well, no mattter what quality fluxxes or system you have. I can do it... but ts messy and not as good as a strong mechanical connection. I have had soldered packs fail sub 800A where the riveted connections went well over 2000A. YOu can never trust a large soldered connection unless it was designed to be soldered, these cells were never designed to solder.

I have began using nickel plated die stamped bus connections. Slather them in Penetrox or Wurth right b4 the final assy and insulation polyimide. I am very sure the bus can take the full continuous powr of the cell. The resistance ( of the connection) is in the pico ohms and is easily measurable in situ.

I built pack like this that took everyday environment for two-ish years now with no corrosion... rain, snow, baths, still report the exact same IR of the baseline test.No lost capacity.

I buy Flexi-bar (flexible high current machine hook up bus bar) in masse and take them apart for the plate inside. I have a stamping machine that punches the little fangs for the (copper) rivets.

https://www.galco.com/buy/ERICO/534008?source=googleshopping&utm_source=adwords&utm_campaign=&gclid=CjwKCAjw1uiEBhBzEiwAO9B_HfDEJMYbpu4eeb3LgSwSolE4thSuYQc7XMH1jkV9caPl2CAByn2kphoCUeAQAvD_BwE

I can easily overwhelm every amp measuring device I own with the correct sized (buss) system without the bus creating heat upon discharge ( or going ZAP with a flash).. this is bad and to be avoided if possible... . I have also began CNC milling aluminum busses for the SPIM08HP cells in number. I have those dimensions on file. That is how the OEM module was assembled with those SPIM08HP cells. The tab quality on the SPIM08HP cell is finely plated and very (forgiving) thick...

SPIMclamp1.jpgSPIMclamp2.jpg

OEM Module design:

https://cdn.shopify.com/s/files/1/2398/3077/products/SP_1024x1024@2x.png?v=1619122791
SPIM08MOD.JPG
https://batteryhookup.com/products/36v-48ah-1776wh-spim08hp-36v-power-module?fbclid=IwAR1apK2y3xf3WL9MvSxzpSgC26kn3xqT6gmflrpcda2-e_W7SdpvgBhmGns

I dont like those readily available slotted fiber glass plates . I got a few here and they are weak. Typical Chinese thin pcb. You can tell why Chris has stronger ones in his build. If I would do it I would cut out of a good 0.20" fiberglass red backpane material.

I did look at those Termifoil connections, rather expensive and very interesting. You pay for ease of assy. I would like to know how thick/soft/malleable they are, the datasheet does stipulate they are plated ( nickel) copper.

Here you can see a progression of the steps in making my homemade connections. I cut the plate on a band saw and stamp them out with a set of wodden and metal die on an arbor press with good successes so far.
 

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thank you for antioxidant suggestions, but I am going to solder in addition to screw and brackets.
I successfully soldered Nissan Leaf copper+ aluminum tabs , I am sure I can solder Volt cells also.
again
those Volt cells are already bolted together
 
Thanks for posting all of that, DogDipstick.

I have heard of spot-welding pouch-tabs together, but I have not tried this myself yet.

The reason I havent gone out of my way to try it first hand, is because it would make it more difficult to swap-out a bad cell, which is a major benefit of clamped-tab pouch cells.
 
For my pouch SPIM08HO packs, I now use this method.
I had been using homemade aluminum clamps with great results also, but wanted something simpler.
I have found the described assembly is VERY easy/fast to assemble&teardown packs.
These are used for my 800W trike builds which draw 30A max.
I use a 5mil copper sheet that I cut into strips the length of the tabs and wide enough to fold over top of them.
Tap wires are simply soldered directly on each copper strip with a drop of solder.
IMG_0700.JPG
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Here are the clips. The clips simply clamp the copper tight against the tabs.
https://www.amazon.com/Dispenser-Handheld-Stainless-Plastic-Student/dp/B08ZS86R5Y/ref=sr_1_2?dchild=1&keywords=clam+clips&qid=1620789524&sr=8-2

Reliable, cheap, VERY easy, no special tooling or casements.
Once I assemble a pack, I place nylon cutting-board pieces cut to the size of the cell on bottom/top of pack and shrink entire assembly. Done!
 
Here's something I did for some re-purposed Fisker batteries. Stock modules are 7s,3p A123 pouch cells. The tabs are welded to nickel bus strips and very short. One cell in a module is bad, so the trick is to bypass it. I took a short piece of solid 8ga copper wire and hammered it flat so it just barely fits in the space between tabs. Then I soldered a stranded wire to the end and drilled a couple of holes for blind rivets. There was just enough clearance for a rivet to the top of the pouches. I used a drill stop to avoid drilling into a pouch.

Img_1426A.jpg
 
One more thing I wanted to mention for those looking for safe reliable connection schemes for pouch cells. Very easy bolt on construcion.

Check out Panduit SKU: CO35-36-Q (part number).

Easily made into buss stock for the implementation of connection. Copper, mechanical, Single barrel lug, Two hole, #6-#14 wire, Combination stud, 3/16 Offset tongue.

https://www.mouser.com/ProductDetail/Panduit/CO35-36-Q?qs=dj%252BWRu48u8W0XPbp5D%2FFRA%3D%3D


Example:
 

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Great link, thanks! Here's a pic of the HDPE "kitchen cutting board" I used for the 12V jumper-box framework. Also used wood so the threads of the screws would be able to make a firm attachment. But the Gorilla clear glue did not work on HDPE as well as I hoped. I seem to remember JB-Weld "plastic formula" worked OK. I will continue to search for a strong glue for HDPE...

If you look close, you might be able to see the slots on the far panel for the pouch-cell tabs. LTO chemistry, so six cells.


BatteryJumperBox1.jpg
 
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DogDipstick said:
One more thing I wanted to mention for those looking for safe reliable connection schemes for pouch cells. Very easy bolt on construcion.

Check out Panduit SKU: CO35-36-Q (part number).

Easily made into buss stock for the implementation of connection. Copper, mechanical, Single barrel lug, Two hole, #6-#14 wire, Combination stud, 3/16 Offset tongue.

https://www.mouser.com/ProductDetail/Panduit/CO35-36-Q?qs=dj%252BWRu48u8W0XPbp5D%2FFRA%3D%3D

That's pretty nice, but marked obsolete.
There are similar two-hole solder (or crimp) lugs/terminals
 
I am working on something like this as well for high power tab connections.

I will post my work shortly.

Thanks for this thread.

-Arlin
 
Wanted to bring this thread back up for general interest in flat pouch cells and building methods. Seems to me, that you don't see pouch builds nearly as common on youtube and other sites because there's no defined "Right way" to do them; some are poor at soldering, some seemed to have used paper hole punchers and copper rivets, some even use basic metal clips. Lots of information is from Dog Dipstick; DrAngel's massive battery thread has some information, but I'm not sure if new methods should also be considered since we have largely moved away from soldering.

Galvanic Corrosion Resistance information and what coatings to use: https://endless-sphere.com/forums/viewtopic.php?f=14&t=115309&p=1705975&hilit=pouch+cell#p1705975
  • Dogdipstick comes in clutch with coating recommendations that conduct but don't allow some forms of oxidation.
CLAMPED TABS by RIPPERTON, argues for aluminum clamping to dissipate heat: https://endless-sphere.com/forums/viewtopic.php?f=14&t=114032&p=1686144&hilit=pouch+cell#p1686144
  • Uses a jig to drill holes and bend tabs, then bolts them to an aluminum busbar.
Jonescg Legacy thread: https://endless-sphere.com/forums/viewtopic.php?f=14&t=116615&hilit=pouch+cell

Flippy explains why Tab cooling for prismatics is a poor idea, advocates for copper plates to soak heat away from cells: https://endless-sphere.com/forums/viewtopic.php?f=14&t=112045&p=1659163&hilit=pouch+cell#p1659163

Seems so far, that the best way to control heat and properly use flat pouch is to have a low enough IR that heat isn't generated in the first place, solder your BMS connections, connect cells via clips slathered in anti-corrosives, then compress into a pack using the same polycarbonate plastics used in cheap cutting boards.
 
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