Spec sheet for A123 AMP20M1HD-A

[mjcrow]

I had been looking for this for a while, finally found one here http://www.wheelchairdriver.com/pdf-files/specsheetA123.pdf so I thought I'd share

Interestingly they make no mention of rated charging or discharging rates like they do in the 26650M1 spec sheet, maybe there is some differences with the APP, AHP etc versions.

 

[whatever]

thanks for posting
the last graph on cycle life, if accurate is impressive, it also will give anyone getting the seconds ( ebay/cellman etc) ability to roughly calculate how many cycles the cells already have on them.

 

[mjcrow]

Must be a few resellers of the B grade stuff out there, Mavizen recently posted this on their website:

Mavizen/A123 have been made aware of a number of outlets offering A123 Systems products for sale. These outlets claim to be able to offer vast quantities at very low prices. Some of the outlets for unauthorised A123 products include websites, eBay, and Alibaba to mention just a few.

Working alongside A123 Systems Inc, Mavizen has ascertained that these resellers may be supplying quality control failures, intercepted during the recycling process and passed of as new.

We are concerned for the reputation of our product and services as well the safety of those customers who have been led to believe that these cut price channels are authorised and that their supplies are genuine and safe. A123 Systems Inc., does not supply any product other than through authorised channels. These unauthorised traders represent poor value and are supplying a potentially dangerous product.

Aggressive steps have and are being taken to stop these activities. They pose a real danger to would be purchasers, and in some circumstances could lead to a catastrophic failure.

In the meantime, we would like to remind you that Mavizen is an official channel partner of A123 Systems Inc. and all of our products come directly from the factory and are subject to the quality control and performance that delivers the best performance, safely and consistently.

Please let us know of any sources offering A123 products. We appreciate your understanding and help in this matter.

So if the B grade cells prove to be around 95% capacity, then they should have around 2000 cycles left before they reach 90%, (this of course relys upon the user discharging them @ 1C), but who knows how many cycles till they reach 80%, which if the curve continues as it shows would be another 1500 cycles later, so basically 3500 cycles or close enough to 10 years of daily commute. Seeing as my test cells (neutered with tabs exposed) cost me about $28 each shipped, not too bad if I could get 10 years out of them to 80% capacity

 

[liveforphysics]

This who talk about seconds is propaganda from crooks like Azahar/Mavazen.

Second, you can not predict a cells future cycle life from a starting capacity test. Lol.

These cells are sadly a day late and dollar short of being worth buying anyways. Safer stuff with better capacity and 10x better cycle life is available easier.

A123 is dying. Its making last ditch efforts to move yesterdays tech.

 

[jonescg]

...Safer stuff with better capacity and 10x better cycle life is available easier....

Such as.... ...?

 

[theRealFury]

...Safer stuff with better capacity and 10x better cycle life is available easier....

Such as.... ...?

Ill second that, LFP what is the holy grail of battery tech that is easily available at the moment? I thought that A123 was towards the top of the pile?

 

[whatever]

a123 was way ahead of the rest for years, not sure if anyone has caught them up as yet

 

[miniebiker]

This who talk about seconds is propaganda from crooks like Azahar/Mavazen.

Second, you can not predict a cells future cycle life from a starting capacity test. Lol.

These cells are sadly a day late and dollar short of being worth buying anyways. Safer stuff with better capacity and 10x better cycle life is available easier.

A123 is dying. Its making last ditch efforts to move yesterdays tech.

A123 shares up more than 40 percent

http://www.reuters.com/article/2011/08/11/us-gm-battery-idUSTRE77A30D20110811

 

[heathyoung]

So if the B grade cells prove to be around 95% capacity, then they should have around 2000 cycles left before they reach 90%, (this of course relys upon the user discharging them @ 1C), but who knows how many cycles till they reach 80%, which if the curve continues as it shows would be another 1500 cycles later, so basically 3500 cycles or close enough to 10 years of daily commute. Seeing as my test cells (neutered with tabs exposed) cost me about $28 each shipped, not too bad if I could get 10 years out of them to 80% capacity

The self-serving mavizen propaganda aside - where did you get the 20AH versions for that price???

 

[mjcrow]

I don't actually think you could realistically get 10 years out of these cells, and if you really look at any of the spec sheets and claims made by A123, they are always at ridiculously low c rates, and pretty much any cells will give reasonable life with short cycles and low c rates. My main use for these cells initially will be my Lawn mower conversion (that's if they are actually useable, testing will tell that) and that will see really low use, so cells should last a while for that application. I would never even contemplate the US$80 odd + shipping for cells from Mavizen, thats just nuts.

As to where I got them for that price, the guy who sells them on ebay here http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=250888450176 has a Taobao site (basically a Chinese version of ebay) where he sells two versions of the neutered cells, "unstripped" http://item.taobao.com/item.htm?id=9184129718 and "stripped" http://item.taobao.com/item.htm?id=10178995858. I went with the stripped as 25Y extra is only about $4 and less work for me. You have to buy through a Taobao agent, I contacted 7 of them and only 1 was willing to ship batteries, so I used them, they generally charge about 10% commission, but you can pay with paypal and they were actually really good to deal with, they found out for me for example that the stripped cells are cells that they have tested (not sure how they "test" them though) and found to be "useable", the unstripped ones are basically untested and could be completely dead, your risk. They also sent me a photo once they had received them from the seller. The company I used was Taobaotrends http://www.taobaotrends.com/, although they have just consolidated with their sister site http://www.taobaotrading.com/ . I can post some pics of the cells if you like.

 

[heathyoung]

If there was an easy way to terminate these, you would definitly be on a winner - the tabs are very short, even with the stripped version - I suppose you could use a special aluminium solder, like you would use on old-school lipo batteries, and a custom PCB.

Post up some photos, these are an interesting cell, and if the termination issues could be sorted, a pretty useful source.

 

[mjcrow]

Pics

Larger image Link http://www.mjcmedia.com.au/photos/_MG_2432.jpg

Larger image Link http://www.mjcmedia.com.au/photos/_MG_2434.jpg

Larger image Link http://www.mjcmedia.com.au/photos/_MG_2437.jpg

Larger image Link http://www.mjcmedia.com.au/photos/_MG_2438.jpg

Exposed tabs are average of 7mm high, so surface area of approx 3sq cm per tab per side. I am thinking of using copper bar, threaded to take a screw each side of the tabs.

 

[amberwolf]

If you haven't read it already, there is a thread specifically about terminating these packs, from back when Cell-man was able to get them. I don't have a link, but it should be easy to find via google's site search.

 

[mjcrow]

I have read that thread with interest, also someone here (can't remember who) was spot welding them with some success. I really liked the way CroDriver put his pack together here http://www.vst-cars.com/index.php?option=com_content&view=article&id=66&Itemid=61, obviously I wont be going to this level of sophistication, but with short tabs I think clamping with solid copper is probably my best bet, also the chances of a dud cell are pretty high, so being able to swap out cells would be an advantage.

 

[isaac_alaska]

that is by far the largest vehicle BMS or battery pack i have ever seen. The city i live in has the world's largest battery, it takes up a city block . but the one in the car is a close second wonder if he's selling copies of his BMS system?

 

[mjcrow]

He builds nice stuff, that's for sure, I think for his third pack he used cellman's cells.

 

[amberwolf]

Somewhere, I have seen some large-format pouch cell like the A123 that has what look like brass tabs welded fully (not just spots, but full clamped-welds) across the full length of the existing tabs. Since they're brass, they could be used to either clamp together or solder, easily enough.

 

[jimw1960]

I have messed with a few of these tabless cells and found one very important thing to be careful about. The foil pouch material on these cells is connected to the negative anode side of the battery. It is separated from the positive terminal by a thin layer of teflon and is also coated with a plastic layer on the outside. On the regular tab cells the teflon insulator sticks out from under the foil about 1mm up the terminal to keep them well separated and there is plenty of tab to work with without getting your termination too close to the foil pouch material. On the short tabs, when you grind down the foil material and its underlying teflon insulator on the positive termainal, you don't have so much room to work with and it makes for a potential short circuit if any solder or screwed-on terminal lugs should come in contact with the pouch foil. Therefore, it is very important that any kind of solder or clamp used on the positive terminal have at least 1mm of clearance from touching the foil pouch material. Any overlap and it could touch the now-exposed edge of the foil or wear through the outer coating and short out the battery.

 

[zEEz]

ADDENDUM:

I read the taobao offer of the chinese guy selling this untabbed cells:
he is showing in photos the Internal Resistance tests that are confirming Rint
of around 2 to 9 milliohms per cell ...
Not too good, not too bad, but definitely tolerable values ... :wink:

have fun!