A123 20AHr Pouch Cell Battery Build & Info Thread

[999zip999]

Drutledge and Ohzee how are your packs working out and what is the max amp draw ? Any problems ? And what would you do different in that build. I'm going to follow in your foot steps two 12s for a 12s40ah or a 24s20ah flexable. 40 amp max draw.

[ohzee]

Yesterday I finally drained my pack.. It's a 20s1p. I tried to not pedal as much as I usually do so I could empty it out as it was quite a feat.
I did 29 miles and used up 17ah out of my pack. I have the signalab BMS high rate which max's at 60 amps and I used it on my yuba mundo mid
drive kit so an 8t . I have the CA limit to 30 amps so I don't burn up the motor.

Once home I sat down with the battery and tested all the cells to see where they were.. I had one cell near the middle of my pack which was
noticeably lower then the others. I may look into replacing and will be glad I covered my battery with plastic wrap before any tape.

I am very happy with this battery , but my amp draw is quite low.

[oatnet]

and used up 17ah out of my pack.
I had one cell near the middle of my pack which was noticeably lower then the others.
glad I covered my battery with plastic wrap before any tape.

At 30a/1.5c, I bet sag was minimal, a great quality of these cells.
I use a standard 80%DOD on these cells, so I would have stopped the test at 16ah - at 17ah you are into the knee of the discharge curve. What were the voltages of the good cells vs inferior cell at the end of discharge? Did you confirm voltages on the cells before your test, to make sure the BMS had accurately balanced them?
I use quality blue painters tape for the same reason you used plastic wrap - lasts for years, comes off in seconds.

-JD

[ohzee]

The low one was 2.62. The others were 3.04, 2.94, 2.95 all in that area. This is at rest.

I did test my battery previously when all charged and each time the BMS had them where I thought they should be
3.5x to 3.6x.

I do love these cells. They are turning out to be everything I thought they would be and I agree about stopping where
I did. I honestly just wanted to verify the BMS cut off power

There's nothing better then plugging in the charger in my garage and trusting it to turn off when it should.

[999zip999]

It conducts thru the aliumium bar as a buss.

[jonescg]

Hi Guys,
I wrote to EIG asking about some sampler cells and tab dimensions and stuff. They said sure, sign this mutual non-disclosure agreement...

I went ahead with it, cause I really want to play with these cells. But since I don't want lawyers getting all gloryhole on my ass (thanks for the image, Philistine ) I probably won't be sharing their information. I'll happily share mine though. What was I saying about gloryholes?

[999zip999]

Would it be better to connect the taps direct to each other with a alum-oxy paste, then use the aluimun as a buss bar. It does make a handy sense wire(s) connection point. I guess I'm asking what rate of discharge in amps can a battery made druledge method can handle ? 100amp ? With 12s.

[jonescg]

Not quite sure what you mean Zip. You mean doing away with the copper bars?

[999zip999]

I'm talking about the Drutledge pack build and he has the tabs on each side of the 1/4 in. alumiun bar. In a 1p build wouldn't it be better to connect the taps togethere with alium-oxy for a better contact. Or would it matter as with a alumium buss bar in the center as i'm only drawing 60amps. How many amps can be drawn thru this pack build on a 12s ? I just going to follow his foot steps as it has a good place for sense wires and end termanals.

[999zip999]

Sorry Jonescg There is 4 builds going on in this thread from Jd's to Drutledge's and a few tab connect's. I like it kiss and to be able to repalce a low cell as they did come out the back door.

[ambroseliao]

Got my 14 cells from Oatnet so will be starting my pack build.


https://lh5.googleusercontent.com/-GMa9EC15cPA/T-cWTQMUIcI/AAAAAAAAR9g/vlozCo0BTys/s144/photo%25201.JPG

[999zip999]

Wish my cells could hold 33.09v. What if there was a 33.09v and 20ah cell.

[ambroseliao]

Oops. I have high hopes for these cells. Perhaps a bit too high. Corrected now! Thanks for catching it!

[salty9]

Don't laugh too hard, this question is asked from ignorance. Would it be useful to include a pressure sensor in
a pouch cell battery?

[999zip999]

Don't even think compesion is that much of a biggie as just compession is enough. If a cell goes to puff it's becase it's inside the cell and more persure wouldn't stop it. I think I'm right ? It's worth talking about.

[dnmun]

.

[999zip999]

O.K. how much compesion is needed ?

[toolman2]

O.K. how much compesion is needed ?

about the amount you can get by taping them as tight as you can by hand, with end plates from say 1.6mm fiberglass sheet or similar.
i would prolly not bother with a readout of the cell pressures, what if you were distracted by one of the 24 readouts whilst riding and had an accident..

[jamo96]

How wide is the widest bit which you can put these cells in a box? I assume that you can fold the skirt around the actual cell?

[oatnet]

The "skirt" is already folded, so go with the number you already have for width.

I've charged these cells loose on a desk - albeit in parallel at a slow rate - and seen no sign of swelling.

[ohzee]

Yea the compression posts confused me as I just used different types of tape to hold my battery together.

Something I had happen in one of my 12s packs I had build before.. One of the cells swelled so bad I had to tear
apart the battery and remove it. It was ballooned as much as the cell possibly could go. This is 1 out of 32 cells
I had bought so I still feel great about these cells. It started when I discharged as that's when I noticed it.

Still my 20s pack is working flawlessly and I expect the next pack I build will as well.

[999zip999]

I think there is something wrong inside a cell when it swells and compession will not stop it from going bad. But will stop the pack from expanding and tearing tabs or deforming the pack. The buss bar should be taken off first then take the compession plates off last. If you take the plates off first and a cell or two expand they will tear the others taps as they are bolted togethere at the buss.

[ambroseliao]

How wide is the widest bit which you can put these cells in a box? I assume that you can fold the skirt around the actual cell?

You can fold the crimped portion of the pack a bit. I measured one of my A123 20Ah cells and the width you requested is almost exactly 6" or 15.2mm.

See below:

CF9iL.png (18.89 KiB) Viewed 699 times

updated to correct typo!

[docnjoj]

How wide is the widest bit which you can put these cells in a box? I assume that you can fold the skirt around the actual cell?

You can fold the crimped portion of the pack a bit. I measured one of my A123 20Ah cells and the width you requested is almost exactly 6" or 15.2mm.

See below:

CF9iL copy.png

I'm sure it is a typo but didn't you mean 15.2 cm=6"?
otherDoc

[ambroseliao]

Right! Oops. let me fix it.

Edit: It's now corrected. Thanks.