Quick question about pack design idea

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garolittle

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Question for the experts: Assume the use of 32650 Lithium Iron Phosphate (LiFePO) Cells. The cells do not have the original plastic a ring gasket but will be re-wrapped with have a paper “stick-on O-ring gasket” (see green arrow below) as well as a 3-D printed gasket (red arrow below) that will sit on top of the paper stick-on. Finally, a .25 mm thick copper sheet will be spot welded onto the cells using a pulse arch welder. There will be an aluminum bar (yellow arrow below) which uses rivets to connect to the other side (anode) of the pack (ie the rivets run through the spaces between the cells to connect to the other (negative/anode) side.

What are your thoughts on this design?
EA2B0380-3E9B-4958-948F-F8FA1263DE63.jpeg
 
Please link to sources for factory-new cells, not secondhand/dismantled.

How close are the LFP 32700?

Also link to the "pulse arch welder"? Hard to believe it can weld the copper directly, no nickel in between?

Is there much vertical gap between cell end surface and copper sheet, height of the two gaskets?

How are you getting the re-wrap done? Shock/vibration if the cells are rubbing? Do you know if the cell walls are positive or negative?

I don't understand the electricity flow using those aluminum buss bars plus "rivets", if there is copper sheet same below as above.

Have you got a diagram showing the positive/negative direction, the gapped shapes on both sides?

And given copper sheeting, why also add the aluminum buss bars?
 
john61ct said:
Also link to the "pulse arch welder"? Hard to believe it can weld the copper directly, no nickel ….

Answer: Sunstone Pulse Arc Welder PA 250i ….where is the link https://sunstonewelders.com/products/battery-welder-systems/omega-pa250i-copper-battery-tab-welder

I will have to get you the responses to your other questions. Sincerely appreciate your comment.
Click to expand...
 
john61ct said:
Please link to sources for factory-new cells, not secondhand/dismantled.

How close are the LFP 32700?

Also link to the "pulse arch welder"? Hard to believe it can weld the copper directly, no nickel in between?

Is there much vertical gap between cell end surface and copper sheet, height of the two gaskets?

How are you getting the re-wrap done? Shock/vibration if the cells are rubbing? Do you know if the cell walls are positive or negative?

I don't understand the electricity flow using those aluminum buss bars plus "rivets", if there is copper sheet same below as above.

Have you got a diagram showing the positive/negative direction, the gapped shapes on both sides?

And given copper sheeting, why also add the aluminum buss bars?
Click to expand...


These are the purchased batteries: https://www.alibaba.com/product-det...35675.normal_offer.d_title.7a40369aCnGv32&s=p

Gaskets can be up to .62mm thick, 3D printed. Currently looking at either TPU or PETG for this.

Cell walls are negative. All cells are facing the same direction (each pack is 1s36p). Primary concern is shorting between the copper positive plate and the negative potential rim of the battery.

The aluminium bus bars are intended as a contact surface for a connector to be inserted between. (As seen below)

Aluminium was selected as a compromise on cost, the copper connector is intended to carry the bulk of the current between packs. Nickel plating is an option if corrosion / corrosion between different metals in contact is an issue.
 

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To me, it looks like you are designing a 1S 36P pack that's short circuited.

Spicy!
 
garolittle said:
Sunstone Pulse Arc Welder PA 250i …. https://sunstonewelders.com/products/battery-welder-systems/omega-pa250i-copper-battery-tab-welder
Click to expand...

Wow! pricing ballpark?

 
relevant thread, no spot-welding, but the "dimpled copper" might still be of interest

https://endless-sphere.com/forums/viewtopic.php?p=1680257#p1680257
 
Hi, I'm working with garolittle on this project. The packs will be used in a hybrid diesel/electric telehandler. Final configuration is 196s36p of the 3.2v 6Ah cells. Total 627.2 v nominal, 216Ah.

Yeah, maybe a bit big to use as a Ebike battery. Well, unless you want to carry around 995 kg of batteries.
 
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