Options for A123 LiFePO₄ 20Ah pouch cells parallel and series connections?


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floydR

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Aug 23, 2017
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Options for A123 LiFePO₄ 20Ah pouch cells both in parallel and series connections:
Since a low cost laser or ultrasonic welder is not within reach, spot welding (resistance welding) is an option.
Resistance welding is referenced in the pdf linked in this post by AntaresAdroit https://secondlifestorage.com/index.php?threads/getting-ready-to-dive-into-lifepo4.11287/#post-79100 but not exactly spot welding.

Another option is friction fit using holes punched in the tab with corresponding holes in copper/aluminum pieces secured by pop rivets or screws.

Another idea from AntaresAdroit is to use edge card connectors. https://secondlifestorage.com/index.php?threads/getting-ready-to-dive-into-lifepo4.11287/#post-79190 Which would work great as most have gold plated contacts and could handle the current. a 4s1p pack would use three edge card connectors

Clamps were mentioned in this post by jgilly69 https://secondlifestorage.com/index...4-pouch-cells-20ah-compacts.11280/#post-78936

Later floyd
 

lucasd05

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Oct 1, 2021
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Are you zeroing in on a build concept for these? I see there are also some 37ah versions of these currently available - that equates to almost half the number of connections to fuss with. It might save some time and materials if their discharge profiles still meet your use case.

Update - It looks like BCH made me a liar. The page is gone. They must have sold out. :p
 
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floydR

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I already have the cells so am planning ,have to test the cells as of yet. Need a suitable 1s case to put the cell in prior to testing.

Later floyd
 

Redpacket

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Maybe a combination of punching holes in the tabs + bolts/screws & using stacks of fibreglass PCB strips for contact & spacing between cells might work?

For testing, could you just use a couple of pieces of 3/4 inch ply & some clamps to make a "battery sandwich" (keep that compression these cells apparently need?)?
 

jgilly69

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Aug 11, 2019
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I am going to try and design a PCB that will connect like this -- See video (Some Korean builder). Probably another week or more before I get the prototype sent out for manufacturing.

View: https://www.youtube.com/watch?v=bFHrCq2O_GM


I made a little 3D holder for the compact cells, but once I saw we need to do full compression my plans are changing on how to mount these. IMG_36042.jpg
 

floydR

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I am going to try and design a PCB that will connect like this -- See video (Some Korean builder). Probably another week or more before I get the prototype sent out for manufacturing.
I will watch again later thanks for the link.
A 4S will fit in one of these. https://www.batteryspace.com/plasti...ct-to-build-12-8v-20ah-prismatic-battery.aspx
Add some 1mm EVA foam and this is rock solid.
Sounds good. I might do a 2s2p for my 6v motorcycle.
Later floyd
 

Redpacket

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Those bars (3?) running across the cells might be pressure points on the cells?
PCB board idea looks good - guy in video REALLY needs insulated tools (& socket set), shorting risk is pretty high!
 

nbtesh

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Feb 9, 2022
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This was my solution. mechanical clamp.
 

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Redpacket

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Neat way to join the cell tabs :)
But where only part of the pouch cell face is covered by the wood is not good - you will have problems there!
Also, I hope the cable ties have enough stretch to allow normal cell size expansion & contraction during charge/discharge cycles.
It would be better to have some foam in the stack to allow for normal size change.
See pic:
pack compression.png
 

nbtesh

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Feb 9, 2022
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Thanks for the Critique..!
Was dificult to source 4” lumber locally. Used 3”
I tested the Zip Ties and they have good strech.
Im hoping for 5 years Lifetime.
The small ones are engine crancking and the large ones are Golf Cars conversions.
 
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