A123 20AHr Pouch Cell Battery Build & Info Thread

[dnmun]

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[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 680 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.

[agniusm]

I was thinking of going with brass because it solders easily. The solder is really just there to keep the block from moving when you fold the tabs over and tighten down. The other benefit of brass is I have chosen 6.3 mm square brass bar (standard size) so no additional machining is needed - just drilling and tapping. I have improved the design of the PCB a bit too so that I have room for two 7-pin JSTs and a 6 pin JST (19s all up). So the blocks will need to be able to conduct reasonably well.



Anyway, the cells cost a fortune, so I don't think it will matter right now

Edit: Added top secret PCB design which is going to earn me billions

Hi. I would reconsider using brass. Have you calculated resistance on brass? I did and it is less than aluminum. Second is weight, trust me it adds a ton to the pack, bad for EV use. If you going to use brass flat bar to connect cells in 3,4,5P configuration which i bet is meant for cars and bikes you will have problems regarding conductivity. I tested mine with 211amps and my blocks which are just clamping tabs get worm. Solitons and zillas go beyond 1k amps Just my point of view.

[ladz]

It seems there has been a lot of discussion and confusion about where to source these 20ah pouch cells. There also seem to be at least two common revisions, the AMPxxx ones and the APPxxx ones.
I'm going to put together 2x 8s1p stacks of these (if I can successfully buy the cells!) to make 48v. I have a fabrication shop, so constructing the box and mounting/wiring will be easy after reading all the great ideas people post.
There was a group buy that happened in April.
There is ebay.
There is Victpower
There is a123rc
There are some random people on Taobao.

After reading a lot, the easiest and most sure thing seems to be buying them from a123rc to ship to USA. They are also one of the few to answer email.
Are there any other group buys or reliable sources besides this?

[ambroseliao]

They are not online right now! Website 404.

http://www.a123rc.com/

[oatnet]

They are not online right now! Website 404.

http://www.a123rc.com/

Wtf, that is the correct URL... Wonder if they are having computer issues, or vanished into the night.

[jonescg]

Hi. I would reconsider using brass. Have you calculated resistance on brass? I did and it is less than aluminum. Second is weight, trust me it adds a ton to the pack, bad for EV use. If you going to use brass flat bar to connect cells in 3,4,5P configuration which i bet is meant for cars and bikes you will have problems regarding conductivity. I tested mine with 211amps and my blocks which are just clamping tabs get worm. Solitons and zillas go beyond 1k amps Just my point of view.

The brass won't be taking any of the current - the 1.6 mm copper plate goes on top to clamp the tabs down - this is what will be taking the current. The brass is simply there to provide good tension when tightening the copper down. Brass is a pain to work with, but that's why I'll get a fabrication shop to do it for me. The other benefit of brass is that it can be soldered down onto the pads on the PCB to hold it in place. Then, traces can be run from the pads to serial sockets.

As for weight, yes, I know it gets heavy, but the brass component of my car battery will really only be adding 3 kg to the whole 25 kWh pack. The copper will be an additional 7 kg, so 10 kg all up. I don't think it will matter much on a 950 kg car.

[agniusm]

Hi. I would reconsider using brass. Have you calculated resistance on brass? I did and it is less than aluminum. Second is weight, trust me it adds a ton to the pack, bad for EV use. If you going to use brass flat bar to connect cells in 3,4,5P configuration which i bet is meant for cars and bikes you will have problems regarding conductivity. I tested mine with 211amps and my blocks which are just clamping tabs get worm. Solitons and zillas go beyond 1k amps Just my point of view.

The brass won't be taking any of the current - the 1.6 mm copper plate goes on top to clamp the tabs down - this is what will be taking the current. The brass is simply there to provide good tension when tightening the copper down. Brass is a pain to work with, but that's why I'll get a fabrication shop to do it for me. The other benefit of brass is that it can be soldered down onto the pads on the PCB to hold it in place. Then, traces can be run from the pads to serial sockets.

As for weight, yes, I know it gets heavy, but the brass component of my car battery will really only be adding 3 kg to the whole 25 kWh pack. The copper will be an additional 7 kg, so 10 kg all up. I don't think it will matter much on a 950 kg car.

Ok, missed that part, was looking at the image . Copper will be best for this and 10kg is nothing for sure.

[999zip999]

I order from McMaster for the Drutledge build tuesday 2pm and got it 4pm wed. Wow. Charging 6s with 4 voltfreacks 3.65v2a. Have a hyperion but love those little things for A123 and headways voltage. See how long this takes.

[999zip999]

I found 1/4 od x.170 poly tube I think for ice cube maker. Perfect even fit's thru the punch hole in the tabs ( paper punch ) one peice.

[ohzee]

Yea I used the same stuff for my build worked pretty good for me.

[999zip999]

My fluke 113 won't pickup the 3.32v, But my free ( coupon ) H.F. m.m. does ? ? Can't wait for those voltfreaks and hooked up the 1420 for 11a on 6s to 3.62v. An old 10in. carbide 40t on a chop saw cuts the 1/4in. alumiun bar just fine.

[999zip999]

Drill the holes in the tabs a little bigger as to free them up. Do I use the grease ? What grease ? local hardware stuff or home depot or forget it ?

[docnjoj]

I'm waiting for my agniusm kits to arrive but in the meantime I;'ve used my No-Ox ID-A on all my plugs and outlets outdoors and by the pool. It seems to really help conductivity since when I do a before and after with a Killowatt meter the current draw seems to be about 1 amp in 10 lower. Maybe a fluke but I will swear by this stuff and use it on my 12S battery when the kit comes. Seems like good stuff.
otherDoc

[ambroseliao]

I bought some Noalox in preparation for my A123 build. Has anyone else used this stuff?

http://www.idealindustries.com/prodDeta ... dId=noalox

Ambrose

[999zip999]

Yes Ambro i think that's the stuff from home depot. Is there some high temp. or something ?

[999zip999]

O.k. the drills don't work for the tabs even the drill point, but from dewalt little different center drill. I use a 3m paper pouch wit the two outer punches taken out, perfect. The bule plastic the drill drifted even in a dril vise with 3/32 pilot hole ? No problem. The 3/32 drill for the 4/40 is small so ream the hole with the drill or find the right drill. Put a wooden cloths clip on 6s parelle at 3.6v for balance.