Is there interest in a group buy of A123 20ah prismatic pouch cells?

With all the info and detailed photos provided to build your own HV battery pack at Plug-In Supply Installation Instructions And the very detailed instructions provided by MJFROG at PIS 4kwh PHEV kit assembly and installation odyssey | PriusChat any mug should be able to build their own PHEV kit. However pouch cells are not used by pluginsupply and are a bit more complicated to put together.

 

"bricks" is the EVTV terminology they have used....... I have not decided yet 8ah-----thru 200ah is out there and CALB is introducing new cells..

 

well only the new cells jack presented are anything close you can use if you deside to go as low as 8ah....
you do know about 10c and 20c and 5 x ratings?
these A123 pouches are one of the best to that regard.
you need like min 40ah bricks or best 60ah ( for better life ) to do that with those older bricks.
these new ones jack presented are a lot better.

 

Here's a good deal.

A123 20Ah systems prismatic pouch cell Type automative class lithium ion cell-in Rechargeable Batteries from Electrical Equipment & Supplies on Aliexpress.com
Shenzhen Victpower Technology Co., Ltd. - Small Orders Online Store, Hot Selling battery,ebike li-ion battery,48v 15Ah li-ion battery pack and more on Aliexpress.com
76 x A123 20ah pouch cells at US$19.02 each plus
2 % discount for 10+
DHL Express to USA US$408.39 3-7 days delivery
Total - US$1825.03 including delivery. That's US$24.01 each including delivery.

Can you beat that!

 

That's a very good price but, do we have any purchaser already for comments?

 

I find your claim a bit hard to believe. I have bought cells that had no tabs but they were advertised as such.
Not all A123 cells come from China. If you look at the picture provided in the attachment of the A123 cell is marked "MADE IN KOREA".

 

I see a lot of people claiming to measure 18-19 Ah from these cells. Can anyone describe the test method in detail? Where are you getting technical information on the cells?

 

Ideally, you should only charge to 3.60, cutting back charge current at high SOC until terminal Voltage is 3.60 with 1/20C (1 amp) being drawn. Simplest just to CV the cell at 3.6V and stop charging when current falls below 1A. Exceeding 3.60V a tad during charging isn't the end of the world, but there is Li plating above 3.60V and that costs calendar life. At 2C, I would discharge until terminal Voltage is 2.0 or even 1.5. The standard for 0% SOC is 2.5V OCV, fully rested. There is no harm in taking these cells that low, but NEVER take them below 300 mV or drive them negative. My guess is that the cells you have are just fine and actually have ~20Ah of capacity. If the tabs are partial, these have probably been rescued from scrapped modules. If tabs are complete, the parts may well be stolen if they test OK, but there could be latent issues that may or may not become a problem as time goes on. A cell with no tabs is useless at best, dangerous at worst. I would avoid these for any kind of use except maybe bench testing.

The holes and slots punched into the "-" terminal is a fuse. Don't defeat these!

 

How do you determine the rating of these fuses?

 

I'm not sure offhand what the fuse is rated for--probably a hundred amps or more. [Edit: Actually, after thinking about it, it's more likely 400 Amps or more.] It's meant as a last-ditch safety device in case of a hard short across the tabs, like if you drop an uninsulated wrench onto a pack. Suffice to say, if you pop that fuse, you have averted a larger problem caused by exceeding the safe output current of the cell.

 

Sounds like the zipper fuse to me. Got a pic?

 

Here's a pic I have. This was pulled from a complete module. Weld strap remains at the ends of the tabs, holes and slots on the right hand terminal are the zipper fuse.

 

Me personally, I've never built a pack from scratch (though I do plan to build a small one for a bike project). I'm not sure the company has ever built a pack without them. Packs with cylindrical cells have these built into the weld straps, usually at the cell AND module level. These really are critical safety devices. I've never seen a prismatic one blown, but I have seen it with cylindricals (never with Hymotion though, which usess 26650 cylindrical cells). Usually the result of something getting where it should not be, either in the field or on the bench. Had one pop in my face on the bench once, far preferred that to a destroyed cell or a destroyed face.

 

My Hymotion pack is only charging 3.6kwhr for a full charge after about 900 full equivalent charges. I think I started out at 4.95kwhr. Can a technically trained Tek. dive into these packs and replace bad cells, or is it a real hassle, and/or too dangerous. And at what point would you recommend diving in on a pack.

 

Start a new thread on this. I'll respond.