A123 20AHr Pouch Cell Battery Build & Info Thread

Price has come down on the A123 cells with the short tabs. I just purchased 13 cells at $14.70 each from Victpower.

Looking forward to building my own pack. Some really great ideas in this thread and forum. Contest is on to build the easiest to assemble and disassemble, safest and least expensive pack design. LOL.
 
Really great idea from Zappy. He uses 10mm vinyl tubing cut to length to cover the tab connections. That is a simple, easily removable and safe way to keep from having 20 amps flowing thru your body, especially while building the pack. Just ask Michael2008 and see his post above.

Now I need to run down to Home Depot to figure out the best size for the vinyl tubing. Not sure if the 10mm is outer or inner diameter and the best size in English (1/4, 3/8, or 1/2 inch). Guess it depends on how long your tabs are.
 
Michall2008 said:
megacycle,thank you for the short tab testing im now more confident in my shortys.
2012-11-29033212.jpg
Click to expand...


Nice clean job, but OMG those bare, proximate terminals :shock: on the top row give me chills. You may find that vibration makes the screws burrow through the cardboard on the lower row. When I tried this approach last winter, I used shorter bolts to reduce the chance of shorts, and nylock nuts. It was a lot of work though, so I'd be more inclined to buy the same kit ambrose did, or spot-weld the tabs.

-JD

http://endless-sphere.com/forums/viewtopic.php?f=14&t=29959&start=15#p555239

file.php
 
oatnet said:
Nice clean job, but OMG those bare, proximate terminals :shock: on the top row give me chills. You may find that vibration makes the screws burrow through the cardboard on the lower row. When I tried this approach last winter, I used shorter bolts to reduce the chance of shorts, and nylock nuts. It was a lot of work though, so I'd be more inclined to buy the same kit ambrose did, or spot-weld the tabs.
Click to expand...
I posted earlier about my conversation with A123 management about openning a factory window in Michigan. No go on that, but one of the comments about ebikers building batteries (yea, I know..) was that we'd never get it right, that it took the great expertise of the A123 engineers to get a battery right. At the top of their list was VIBRATIONS undoing a pack or wrecking havoc on the cells. I believe them - they did do extensive testing and do in fact know what will kill a battery pack. So don't disregard that news.

One more thing, a definitive NO to welding from me - again I've posted elsewhere. You want a construct that is reversible, so as to reconstruct a pack, removing & replacing just the cells that have died. See Agniusm's kit for the way to go - just buy the kit or see how to engineer a pack that solves both those issues.
 
Are any of these recent builds using electrical insulating seperaters for cells and tabs or pack ends for compression?

Wood, cardboard, pvc, for tab seperaters, why not straw soaked in petrol, same difference.

The cells need to be kept under compression or they can start to swell.
 
I wish i could show you the 20AH puffer i had, it was about 30+% up size and it was more like a sloppy bag either side with solid middle, but suprisingly it took to being compressed back, on its own, sandwiched between 2 peices of formica and didn't vent any innards, luckily, stupid me, thinking on, havnt monitored it, i think its in a pack now :?

There's quite a few references regards keeping all pouch type cells under compression, even this thread doing a search there's a few hits.
From what were informed its not heavy compression, its just restriction of cell expansion.
Most commercial car packs appear to have this.
Luke gave a lot of pointers way back. Hard to find old threads :?

Going back in this thread, discusses it and cell spacers, personally don't like gp plastics and metals for builds when it all could be made of formica or pcb materials http://endless-sphere.com/forums/viewtopic.php?f=14&t=38876&p=568302&hilit=compression#p568302
 
arkmundi said:
One more thing, a definitive NO to welding from me - again I've posted elsewhere. You want a construct that is reversible, so as to reconstruct a pack, removing & replacing just the cells that have died.
Click to expand...

That's just silly, thinking the spot-welded tabs are irreversible :lol: I keep seeing you speak with such authority about these cells - exactly how many packs have you built with the a123 prisimatics? How many different assembly methods have you tried? How long have you been working with the a123 prisimatics? How often have you experienced the need to replace one of these cells? Because all I see is the (1) pack you built a few months ago :? , and you just posted you don't understand the compression requirements. One would expect you to have actually tried the assembly method you are expressing an opinion on...

-JD
 
My last 24S pack I made with agniusm's kit has only given me 15ah and today 14ah from a full charge.

That's about 20 miles with a 24mph average.. I did pull 20ah from it not long back.. I am right now about
to check out what the cell's are doing with my multi meter..hoping that it's obvious where my problem lies.

Well all cells are 2.94-3.02 so the problem cell is not obvious. Looking at the cell top's I don't see any
puffing etc.. Wondering now how I am gonna find my problem.

I have pulled 20ah out of this pack a month or so ago , but this is now with a new controller pulling more amps.
I may need to use my 20s20ah pack and see what my results are.
 
Are they taking charge ok? What's your regime?
Can't remember, you running cell logs, can you monitor cell volts on the move?
 
hey guys thanks. I am runnin a evaessemble high power BMS and use it to charge.

So yea it's hard for me to monitor voltages while using the battery. I do have a watt meter
i was thinking id use it tomorrow when I charge the pack to see how much goes back in.
 
arkmundi said:
oatnet said:
Nice clean job, but OMG those bare, proximate terminals :shock: on the top row give me chills. You may find that vibration makes the screws burrow through the cardboard on the lower row. When I tried this approach last winter, I used shorter bolts to reduce the chance of shorts, and nylock nuts. It was a lot of work though, so I'd be more inclined to buy the same kit ambrose did, or spot-weld the tabs.
Click to expand...
I posted earlier about my conversation with A123 management about openning a factory window in Michigan. No go on that, but one of the comments about ebikers building batteries (yea, I know..) was that we'd never get it right, that it took the great expertise of the A123 engineers to get a battery right. At the top of their list was VIBRATIONS undoing a pack or wrecking havoc on the cells. I believe them - they did do extensive testing and do in fact know what will kill a battery pack. So don't disregard that news.

One more thing, a definitive NO to welding from me - again I've posted elsewhere. You want a construct that is reversible, so as to reconstruct a pack, removing & replacing just the cells that have died. See Agniusm's kit for the way to go - just buy the kit or see how to engineer a pack that solves both those issues.
Click to expand...

Im yet to build but i think the vibration point is valid for ebikes. For me more so because i dont do suspension and i have highly corrugated roads to travel along....and even without those, a bicycle goes through many more impact events (paths,gutters,potholes, being dropped !) than a car with its specially made roads and highly engineered suspension. hmmmm. So how to compress cells and keep them snug with minimal movement - agnisiums kit is good for me in this regard....and the osn


Im looking forward to hearing more about the osn kit.
 
I used the white rails from verical blinds the cheap ones from Lowes for a 12s pack. It's a tight fit with taperware tub lids and yoga foam. The first pic shows the bottom rail with the u-shape cut out to fit in the triangle and the top rail bolted to the top tube. This has the cells suppendit without pessure on side crimp edges of the cells as they are suppendit without touching or resting on the sides on the bottom rail meaning the crimped foil of the cell. The rear pack lays flat with yoga foam and tupper top and bottom with a wood bottom. I also have a white rail to fit at the end you see to get just enough compession so to speak. Still looking for a way for the compression of the pack with out making more size ? This is limited to 12s or less but it is a package and out of the trash stuff so to speak it's a double I-beam with a convectz top so is very strong and can be flex alittle to fit the triangle. AW you must love the recycleing part. Just give me a good dumpest full and see what we can do.





GEDC0171.JPGGEDC0172.JPG
Ya the top rail is always bolted to the top tube with 1/2 inch plastic pipe to wall holders. Them wrapped under brake and shifter wires and over the top tube with velcro 6 straps as I have a roll of 30ft. I have been carriering for 25 yrs I knew I would find a use. I can only get 12s in the triangle with this design.
 
About minimizing vibration and movement .... there are lots of methods posted. If you're embarking on a build, I'd consider your strategy, to prolong the life of your pack. I don't believe its movement of the whole pack that's a problem, but movement of the cells relative to each other. When one's jagging up while the others are jagging down kind of thing. If the tabs are firmly fixed to each other (like in Agniusm's kit) and you tape or shrink-wrap the remainder, I believe you'll be OK. :mrgreen:
 
i just asked victpower for a price for 28 cells. price is 14.75 for a cell with SHORT tabs.
before ordering i want to make sure: i read of no problems with those cells. but they are more difficult to put together to a pack, aren't they? i think the best way is to fold a piece of copper and push 3 selfsecuring m3 screws thru it.
i'm afraid to destroy the tabs when making the holes for the screws, as they are so tiny.
what do you think?
 
izeman said:
i just asked victpower for a price for 28 cells. price is 14.75 for a cell with SHORT tabs.
before ordering i want to make sure: i read of no problems with those cells. but they are more difficult to put together to a pack, aren't they?
Click to expand...
No, not with Agniusm's kit, which many of us have used. In fact, event the short tabs needed further trimming to be the right size to fit the kit. But you have it right, that the tab size is a factor in the method of construction, and not otherwise. The cell capacity and electrical conductance are up to full spec.
 
arkmundi said:
izeman said:
i just asked victpower for a price for 28 cells. price is 14.75 for a cell with SHORT tabs.
before ordering i want to make sure: i read of no problems with those cells. but they are more difficult to put together to a pack, aren't they?
Click to expand...
No, not with Agniusm's kit, which many of us have used. In fact, event the short tabs needed further trimming to be the right size to fit the kit. But you have it right, that the tab size is a factor in the method of construction, and not otherwise. The cell capacity and electrical conductance are up to full spec.
Click to expand...
good to know. i don't plan using agniusm's kit, but using bended copper plates and screws. but who knows. none of those methods seem perfect for me.
 
I got the package from OSN today and am pleased. The circuit boards are carefully cut and Probably done with a CNC cutter of some sort since the lettering is also cut into the boards. Looking at the numbering on the board, it looks like the 12S board that I have is actually a 16S board cut down to 12. The lack of a B+ etch is also evidence of this.

image.jpg

image.jpg

There are also many bags of copper clips (30 in total), stainless steel nuts and bolts and lock washers...

image.jpg

The copper strips are neatly folded over and the holes are cleanly punched out.



This will make it fairly easy to assemble an A123 20Ah pack. I'll be using a couple of Cell Log battery monitors with those tiny terminal rings.
 
cassschr1 said:
When you do, don't let the bottom edge of copper touch the top edge of cell foil.
Click to expand...

If I understand you right, that would be hard since the fiberglass board is between the cell foil and the copper strips.
 
cassschr1 said:
When you do, don't let the bottom edge of copper touch the top edge of cell foil.
Click to expand...
As a precaution against any future shorting, I place a strip of electrical tape across the top of the cells before assembling them into a pack. Cut a length of tape the width of the cell. Cut two slits for the tabs. You get the idea. Takes all of a minute or two.
 
I used a regular hand held paper punch 3/16 in diameter. It is easier to start the holes with a 1/8 punch first. This was in full tab cells, but you still should have about 10mm tab length to work with and the hole is only 4.5 mm or so when finished. Worked out fine for my agniusm packs.
otherDoc
 
I was thinking might be able to get stainless pot rivets through those clamps instead of bolts, they would look pretty specky and low profile, though can't standardize the pressure applied and have to drill them to remove them.
Otherwise mushroom head bolt with a countersink nut to get around this ugly bolt sticking out business.
 
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