Found some A123 AMP20M1HD-A cells at a scrapyard today. How to take care of them?

[CUDAcores89]

Hey folks, i'm building a new electric bike to use to commute to and from where I work every day. I need to build a new battery for the ebike of course, since my old one was sold off to the new owner (after I installed a proper BMS of course, too many idiots out there).

The best place I know of for cheap, high discharge lithium cells in my case and situation is the 18650s inside drill batteries. The other choice is going with a lipo battery, but for my circumstances used drill batteries are MUCH cheaper than the HK lipos.

To elaborate, I frequently visit a scrapyard near my home that take lithium ion batteries, and I get to buy lithium batteries there by the pound. I was planning to go there and buy a ton of lithium drill batteries for $1.50 a pound, build a high discharge pack together and call it a day. Until I saw these:


If you read the title, they are A123 systems AMP20M1HD-A "pouch" cells. They had 5 of these weird 7S packs that looked like this when I got them home:
'

I chose to buy these instead of the drill batteries.
One of the five 7S packs had a really puffed cell, so I just removed it.

After taking apart all the packs, I had a pile of cells that looked like this:


I will test each and every cell to make sure it will get close to 20AH to eliminate any old cells with high IR or any other weird problems from reusing already used batteries just like I already do when I am testing 18650 cells for reuse.

Now I have a new set of problems that I need help with:

1. The tabs on these cells are aluminum, so I can't solder them. Is there any way for me to bolt the tabs together or something since I can't solder them?

2. After reading a bit on the forums here, these cells need to be compressed. Is that true and if so, how would I go about doing that? Although apparently if your load is small enough, cell compression isn't needed?

3. How should I add foam padding to these cells? I know that this is really important to do with pouch cells because they have no structural integrity like cans.

One more thing. I bought roughly 34 of these A123 20AH cells (subtracting the puffed cell) for a total cost of $60. There's no way I would ever be able to find that low of a price for an ebike battery anywhere online, so that's why I like to go around my local area for batteries. Many of the batteries that turn up at this scrapyard I go to are replaced on a calendar schedule by businesses rather than when the battery actually dies for good. If you are running a hospital, you can't have a battery fail on you if it's the difference between life and death. A ton of the batteries I see there are medical battery packs.

 

[Voltron]

Yes, you can bolt them together. Jonescg used custom pcb with slots for the tabs to poke thru and nuts mounted on the boards to secure them, searching his builds will be a great resource for any pouch cell project.

And yes on compression to reduce puffing. I don't have specific numbers... But they sure out a lot of effort into it on commerical car packs. A system when you can let the compression off is good for later rebuilds. It took me hours to yank out a pack that had puffed itself tightly into a big metal battery box on one of my maxi scooters.

 

[CUDAcores89]

Thanks for the help.

I was thinking for compression, couldn't I just use some pieces of 1x6 pressure treated lumber cut to the right size in combination with hose clamps? Seems like a pretty cheap and easy way to do it considering commercial packs use steel ribbon cables running around the pack as a forum of compression.

Then again, if a cell catches fire, wood certainly won't help the case. Although the battery will be inside of a nylon bag, so this might just be a moot point.

I don't have access to many tools so my options for doing something like building a super-fancy custom battery box are limited.

 

[Voltron]

I'd see if you can find a fiberglass or similar panel to cut up.. stiff but thinner than wood. Ratchet straps might work too, with the wider straps spreading the load, if the mechanism isnt too big.

 

[spinningmagnets]

Good deal, those are great cells. If you have any left over, a 4S pack makes a pretty good "solar suitcase" 12V pack. Make up some kind of compression plates to press them together. Maybe 3/4-inch plywood?

 

[999zip999]

I bolted my rabs togethere with aluminum and plastic alternating blocks same size as the tabs with two long bolts for each tabs or 4 bolts all together threaded stock. I put cents wires on my 12s pack they can check what a cell meter. I cut up a plastic container put it on the outside of the pack and wrapped it with duct tape. Wallah is compressed. 1124 cycles 4.5 years later . Compressed. I bulk charge with meanwell 24v and hp 12v power supply @ 16amps. I have a thru the sense wire balance charger used it 3 times. Use as 16s as my two 12s or 24s is heavy. I can use at 90amps. Good luck
There's some good threads on ES for A123 20 ah cells you our pouch cells

 

[amberwolf]

If it's helpful:

Wb9k posted a fair bit of useful info about these cells in various threads.

There are also a number of posts and threads about interconnect methods for these.

Not all the threads will be relevant, so you'd have to poke thru and see what is, but if you search on A123 in thread titles and display by thread, it'll at least bring up most of the ones about these cells. (it'll also bring up the A123 cylindrical cells, but should be easy to see which are those and skip them).

 

[spinningmagnets]

Agniusm was making assembly kits for these cells. You might ask if he is still selling them?

http://endless-sphere.com/forums/vi...id=e7ed1e959ab43987a156becbaa2553f5&start=650

 

[miro13car]

weird,
those cells are missing info on the top
every A123 20Ah I saw has :
- designation of machine on which it was manufactured and 2 digits of production year.

 

[999zip999]

1 aluminum 1 Copper tab. Cannot be solder. Just as long as they are full tabs and not cut out of a car pack with short tabs and a second tab welded on can be dangerous .