Look a at Prismatic Li-ion Cell & Pack Manufacturing Process

[MitchJi]

Hi,

http://www.greencarcongress.com/2010/02/cooke-enerdel-20100223.html#more

A More Detailed Look at a Prismatic Li-ion Cell and Pack Manufacturing Process
23 February 2010

by Bill Cooke

In January, EnerDel hosted a group of journalists at its Indiana facilities and provided a plant tour showcasing its cell manufacturing and pack assembly processes. EnerDel believes its Hague Road plant is the first, and as yet at this time only, plant capable of achieving high volume production of transportation-grade, lithium ion cells within the US.

EnerDel is scheduled to ship its first cells and packs for the Think City EV on 1 March 2010. The lithium-ion version of the THINK vehicle will have 384 cells in its 25 kWh battery pack and a range of more than 100 miles. While specific elements will vary by sub-chemistry and company, the general steps behind making a prismatic cell are expected to remain consistent for the next several years.

Green Car Congress appreciates EnerDel’s cooperation in sharing their process with our readers. …

 

[Velocipede]

Why are they still using many small cells instead of less big ones?

I don't get why they don't manufacture pack like thundersky where you use only 1p configuration with the Ah size you need.

 

[pwbset]

Why are they still using many small cells instead of less big ones?

I may be mistaken, but I believe it's a "C" rate issue. Small cells have less internal resistance and can discharge a ton more without overheating. Consider a single 18650 A123 than can discharge 30C or a single Sony/Konion 18650 that will happily chirp out 17C. Etc. I suspect another aspect is that they're allowing for some cells/strings to go bad without effecting performance too much.

If I'm wrong I've no doubt someone will correct and enlighten us both.

 

[pwbset]

Oh.. they're using prismatic pouches.. nevermind. :wink: And 384 cells really isn't that much for a 25kwh pack. Anyway.. I still think it's a "C" rate issue! Yeah.. that's the ticket..

 

[johnrobholmes]

There is the issue of warranty and replacement. If one 20ah cell dies, it isn't nearly as expensive to replace as one 100ah cell. With parallel strands you can at least limp home with a bad cell (string) taken out of use. With only serial strings there isn't an easy way to bypass the bad cell.

There is also footprint and thickness constraints. The thicker the cell, the more heat will build up internally. You can offset this with a very large cell footprint, but the cell becomes harder to handle and manufacture. The prismatics will get very delicate when they are the size of a sheet of plywood Going about this in another way, there are size constraints for specific discharge rates and physical reliability.

 

[BiGH]

cool. I'd like to make my ecar battery pack out of cellman cells

still costs a fortune for a decent sized pack for any lithium cells! :\

 

[cell_man]

Thanks Mitch, interesting document.