A123 20AHr Pouch Cell Battery Build & Info Thread

[999zip999]

Ohzee i'm just going to run bareback as I have 74v konion That works fine so as no need to rush.

[ohzee]

Cool keep us updated bud..

[deVries]

Thought this post should be in this thread too...

I'm not sure if it was this thread or another thread on 20ah a123s that I mentioned I had a spark on one pack when a metal object touched an aluminium tab and part of the plastic outer case. I've just finished off a 48v 20ahr a123 pack and I found the source of this spark.
The plastic outer sleeving of the cells appears to have a connection to the copper in the pack. There is a very very thin ( a few microns) clear plastic that is the first layer touching the the inner cells/tabs. If you interfer with the plastic outer covering when connecting cells together there is a very good chance of developing a short.
I'll give a bit of detail how I found the issue.
In my 48v pack, I needed to disonnect in the middle of the pack for charging ( using turnigy/hobbyking chargers) so that I have two 24v packs for charging.
The high amp switch inbetween the two 24v packs when 'off' I was still getting some voltage going through the pack, hence there was a short somewhere.
The source of the short was where I had punched a hole in the aluminium tab, since my tabs were very short, the hole I punched for a bolt went maybe 2mm across the plastic at the base of the aluminium tab.
After the bolt was done up tight it turns out the outerplastic ( having a connection to the copper somehow) was shorting with the aluminium tab.
With a very small screw driver i could see a tiny spark if I touched the aluminium tab and where the plastic outer casing had been interferred with by my hole punching. I think the aluminium within the plastic outer covering ( probably vapour deposited) being very thin layer of aluminium ( or similar metal) can carry a tiny current ( probably high resistance) so even though its a tiny current the voltage across the short could be quite high.
Any how if any one else has issue with some hard to find shorts, check the outerplastic covering in particular anywhere where its been cut, I landed up using nuetral cure silastic along any parts of the outer plastic that might be potential problem.
Because the plastic layer that insulates the aluminium outer plastic from the cells is only a few micron thick I suspect others will also see similar problems.
Cells that haven't had tabs cut shouldn't be a problem but any of the seconds that have very short tabs may have this issue.
A picture of what i've tried to describe would help I know, will try to organise one.

[999zip999]

o.k. charged my 24s twrice. The first run at 25amp was disapointingS. it went down fast. The second charge a little better, but. I stopped at 3.34v. They charge fast at 12a. to 3.59v then my 1420 shut off at 100%, all very even. Running bareback and all keep balance, but go flat fast. So a couple more cycles. Sorry can't down load pic's. ?

[cwah]

o.k. charged my 24s twrice. The first run at 25amp was disapointingS. it went down fast. The second charge a little better, but. I stopped at 3.34v. They charge fast at 12a. to 3.59v then my 1420 shut off at 100%, all very even. Running bareback and all keep balance, but go flat fast. So a couple more cycles. Sorry can't down load pic's. ?

How many AH or WH can you pull out of the 24s pack from full charge (3.6V) to empty (3.2V)? Is it the Victpower cells?

[dnmun]

lifepo4 is fully charged at 3.65V and considered fully discharged at 2.1V.

[999zip999]

These are victpower cells from the mid west group buy and just want to bring life to them NO ah test as I can feel in my seat they need a few cycle's to get them filled up. Plus they are in tupperware tubs looking for some armor. Waiting for my updated Lyen 12 fet to run my 2810. So no hurry.

[999zip999]

I made the box for the triangle 12s and 12s in tupperware on the rack. Maybe hang on the front ? The third charge as 24s is great 34mph with a bmc 600hs 30amp. 2150 watts. All well balance after ride 8ah. The 1420 balance prefect to 3.59v. Maybe will be better after a few cycles. Maybe go with the 2810 and a 12fet lyen ? Happy.

[999zip999]

24s as two 12s A123 Off charger 84v. Put it on the bike it drop to 80v. and stay's at 78v on the ride for 17,966mah close to 18ah. cells off charger 3.59v after ride 3.2v and it's all done 76v. almost 18ah. bmc 600hs at 27amps. It likes to live at 78-76v. ? That's where the cells live. No bms.

[ohzee]

Some battery porn figured id take a pic of what I have in my office now.

My latest 24s build with agniusm's kit and an evaasseuble 100/150 Amp BMS A123 20ah pouch cells
20s build using compression and a ping high power BMS A123 20ah pouch cells
small one on the left 12s headway 10ah with a cellman low power BMS

[potatorage]

So I've assembled my pack but I just realized I'm retarded, since I folded the positive tab over the negative one, making soldering on balance leads extremely difficult. What are some other ways of attaching balance leads?

[ohzee]

Can you screw a small screw into it ? Post a pic and it would be easier to come up with a better solution.

At least you got it all together ok.

[docnjoj]

When I messed up the traces on my first 6S build I had to screw the wires at the blocks with one of the button screws. I works fine and Cellog shows all 6 cells are fine.For the second 6S pack I clear nailpolished the traces and at 4 cells finished no problems at the euroconnector.
otherDoc

[oatnet]

So I've assembled my pack but I just realized I'm retarded, since I folded the positive tab over the negative one, making soldering on balance leads extremely difficult. What are some other ways of attaching balance leads?

You would be challanged to solder the balance wires to the tabs even if they were not folded, which is why we are folding instead of soldering tabs. If you look at my guides for folded tabs (linked earlier in this topic), you will see I put the balance wire in with the first fold. You could probably pull back the last fold, insert the balance wire, and fold it down again. Unless you are doing some extreme charging/balancing, that will be plenty of contact to carry the current.

[megacycle]

So I've assembled my pack but I just realized I'm retarded, since I folded the positive tab over the negative one, making soldering on balance leads extremely difficult. What are some other ways of attaching balance leads?

Have you got a photo of that issue?

[potatorage]

The positive tab is always folded over the negative tab. I purchased some solder that contains flux advertised for soldering to aluminum, but the joints are extremely difficult to make and it takes forever. Not to mention they aren't very solid either.

[ohzee]

heck id get a small heavy duty whole punch and just attach some small bolt/nuts.

I think trying to solder is out of the question.

[megacycle]

To get around soldering if your having problems, a lot of us are , could put lead between tabs and clamp around tab with a u shape of say copper, and I'm not sure were you live but some countries use earthing clamps to bond items to earth they are a small C clamp with screws for clamping to thin guage items and usually have a ring lug for connection could make them if your your handy, bent copper and set screws.
Another way is a termi-foil crimp (the weapon of choice ) if you can get some, squeeze on tabs, secretions bite in.
Good luck.

[teklektik]

Another way is a termi-foil crimp (the weapon of choice ) ...

Termi-Foil crimp! Who knew?

termiFoilCrimp.jpg (6.35 KiB) Viewed 764 times

[docnjoj]

Another way is a termi-foil crimp (the weapon of choice ) ...

Termi-Foil crimp! Who knew?

termiFoilCrimp.jpg

They were in a thread (this one?) a while back when Peter Perkins posted about them. They ain't cheep and dont exaactly fit the tabs. Also the crimp tool is about 1000 USD. I believe there was some discussion about trying to make a proper crimp tool from locking pliers. Luckily agniusm came through before anyone got too serious about them, but the idea seems sound.
otherDoc

[teklektik]

They were in a thread (this one?) a while back when Peter Perkins posted about them.

Oops - caught as a casual tail-of-the-thread reader!
You are quite right - here's the post - Thanks!

[agniusm]

Why cant it be drilled 3mm and balance wire bolted through?

[megacycle]

If you did end up sourcing termi-foil, which are like $0.50 each or a sample, could be less than a bolt price and are made for foil connections, similar to this and can be pressed on in a vice, besides Agniusm is right about a bolt, termi-foil punctures the tab too, same as a bolt hole would, just won't look as sexy IMO.

[EVPowers]

I've been down the termifoil path guys, and they require a minimum 2,000 piece order.
Price to the consumer would be about $1.25-$1.50 per connector.
Also there is a 12-14 week lead time.

I'd do it, but I'm not sure I'd ever be able to recoup the money.
Anyone wanna' go in on it with me? (Half serious here.)

I have some at my shop and it can be a bit tricky to correctly crimp.
Their "official" crimping is $600+.

You can make a poor man's termifoil connector with some copper and a hammer and nail.
I have pics somewhere around here.

[megacycle]

http://www.futureelectronics.com/en/Tec ... ICS5513395

Go half, 1/3rds, sorry 1/5ths dont need that many yet, got $50 spare.

Because we're on balance leads it only has to take say 10 amps max.
So maybe could use copper foil and a meat tenderizer half