Building a custom battery from pouch cells: what do I need to know?

[clanger9]

I'm on the point of ordering a set of Kokam pouch cells for my electric bike project
http://m.kokam.com/skin/pc_en/img/cell_ ... %29_EN.pdf

If I go down this road, I'll be facing a whole set of new challenges... and opportunities to learn

I have one big question first: Where can I get practical guidance & info on building a custom pack form pouch cells?

I realise I'd be far better off using a pre-built OEM modules, but that's proving very difficult for my challenging specification. So I think I need to go it alone. The learning curve will be steep. How to do the battery connections (spot weld?). How to work out what cooling is needed? How to encase the cells safely in a moving vehicle, etc. I can figure out the BMS, electrical safety and the like, but I'm very much in the dark on the physical aspects of battery module design.

If you know anyone with practical experience of doing something like this, I'd love to hear your thoughts...

[arber333]

I have 85Ah Kokams in my EV. I assembled/glued them with duck tape, specialy on the sides where they are conductive.
For separators between tabs i used 15mm Rohacell hard foam. I will post some photos.
I clamped the cells together with 3x M4 bolts, nuts and washers. Clamping material was alu 15mm x 120mm x 2mm flat. I bored 3 holes in the clamping material first so that holes alligned. Then i punctured the cell tabs also. Carefull, you need some material underneath to prevent contacts with other tabs...

I assembled cells in groups of 8S since they are still easy to handle and i can make BMS for 8S. The end contacts i made from 2mm copper with expressed contact. This had to have enough strength to carry 25mm2 cable for connection. I can now use my pack of 98S cells to carry 250A.
In my Mazda...
https://mazdamx3ev.wordpress.com/2015/0 ... lice-lipo/
And the Pug
https://leafdriveblog.wordpress.com/202 ... batteries/

Here is a similar method of construction
https://endless-sphere.com/forums/viewtopic.php?t=38761

Here...
http://www.metricmind.com/audi/14-battery.htm

Or here..
https://forums.aeva.asn.au/viewtopic.php?t=3709

[clanger9]

That is brilliant Arber, thank you!

It gives me reassurance that it's not a completely mad idea.

I'm planning to build mine from 2p "modules", arranged in one bank of 15 and one bank of 10, giving me 25s2p. 100V is all I need for 35kW...

[LRBen]

Thought I would add to this thread rather than the project thread as it seems applicable to quite a few others using pouch cells.

So I've been working on making up my battery with the kokam cells. From what I have gathered keep them compressed or at least not allowing them to expand is very important.

I was originally going to make up some steel plates to go either side of my 10s modules, held together with threaded bar. However with 2mm plate that was going to add 12kg of weight. I thought about using aluminium along with some CNC fiddling to reduce the weight.

I am now leaning towards making up the modules in two rows of 4 for my battery box, and using 10mm wood sheets in between the modules to help keep the contacts of each module separate and also to help with the compression. Wood is lightweight, works well under compression and really in the case of fire the material isn't going to make all that much difference if the cells are burning.

What do we think? Seem reasonable?