jimw1960
10 kW
webfootguy said:
That looks like one of the "short tab" cells like I got samples some from Linda Lin. He says in the ad he has several to sell.
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A123 20AH cells source?
- Thread starter neptronix
- Start date
That looks like one of the "short tab" cells like I got samples some from Linda Lin. He says in the ad he has several to sell.
miro13car
100 kW
bigmoose
1 MW
Texas what do you think about ultrasonic welding the Al-Cu tabs for the connection?
miro13car
100 kW
I don't have any A123 cells , picture is from EV falcon web site.
webfootguy,
what do you think , what happened to the tabs?
oatnet,
what do yoyu think?
toolman,
what do you think?
look at tabs.
They offer them for 70 dollars.
But shipping is rather cheap not like others.
meter does shows amost 0.5miliOhms, but what happened to tabs, never saw tabs like that.
CM
webfootguy,
what do you think , what happened to the tabs?
oatnet,
what do yoyu think?
toolman,
what do you think?
look at tabs.
They offer them for 70 dollars.
But shipping is rather cheap not like others.
meter does shows amost 0.5miliOhms, but what happened to tabs, never saw tabs like that.
CM
jimw1960
10 kW
$70 is a little pricey, but might be worth it to not have to deal with China. He was charging $80 just a few weeks ago. A123rc.com now has the 15Ah version for as low as $41 if you buy 100--free shipping, too. As far as those tabs in the picture, I would assume that was a cell he used for testing.
webfootguy
100 W
The 0.5 milliohm implied in the picture is probably wrong at worse and misleading at best. A123Systems themselves spec these cells as <2.0 milliohm and the testing I have done puts the cells I got between 1.5 and 2.0 which on spec as far as I can tell (i.e. you will get some loss to heat at very high current draws).
If the picture is representative of what you are getting, then the cells have clearly been gotten by disassembling some existing pack (perhaps used for some OEM testing) or the guy beat the tabs up in testing the cells. If from old packs, it might not be all bad as long as the cells have useful life left (early failures would have been removed for example). But, if the cells have been abused until they no longer match each other (some good, some at half capacity for example) then you will have problems trying to build a series pack out of them. One way to mitigate this is to purchase some additional units beyond what you need to test/match the cells to your purpose but at $70 a pop, that can get pricey. Any warranty or claim on capacity?
If you pay with Paypal or a credit card, you have a way to get your $$ back if you get shipped crap cells (do not meet spec or do not look like the picture). If you wire the money, you are taking all the risk and I assure you that is the last you will ever see of your money regardless of what they ship you. I bought 2 x 20 Ah cells from a123rc.com. Both cells tested at 100% of capacity and did not have any marks on the tabs indicating they were pulled from a pack. Mine also said Made in USA while others got the ones made in Korea. A123rc.com takes Paypal which for me was reason I bought from them. I have had good luck with ebay transactions when I bought something that was not as described using Paypal (seller never responded to me or to Ebay) so they gave me 100% of my money back (and in that case, told me to keep the product). I was just asking for a discount on the price for a "used" product in that case.
If the picture is representative of what you are getting, then the cells have clearly been gotten by disassembling some existing pack (perhaps used for some OEM testing) or the guy beat the tabs up in testing the cells. If from old packs, it might not be all bad as long as the cells have useful life left (early failures would have been removed for example). But, if the cells have been abused until they no longer match each other (some good, some at half capacity for example) then you will have problems trying to build a series pack out of them. One way to mitigate this is to purchase some additional units beyond what you need to test/match the cells to your purpose but at $70 a pop, that can get pricey. Any warranty or claim on capacity?
If you pay with Paypal or a credit card, you have a way to get your $$ back if you get shipped crap cells (do not meet spec or do not look like the picture). If you wire the money, you are taking all the risk and I assure you that is the last you will ever see of your money regardless of what they ship you. I bought 2 x 20 Ah cells from a123rc.com. Both cells tested at 100% of capacity and did not have any marks on the tabs indicating they were pulled from a pack. Mine also said Made in USA while others got the ones made in Korea. A123rc.com takes Paypal which for me was reason I bought from them. I have had good luck with ebay transactions when I bought something that was not as described using Paypal (seller never responded to me or to Ebay) so they gave me 100% of my money back (and in that case, told me to keep the product). I was just asking for a discount on the price for a "used" product in that case.
lesdit
100 W
I've ordered some cells from a guy selling on ebay, the ones with no tabs at all !
He shows examples of having peeled back on the envelope and attaching an eyelet terminal.
Should be ok for lower current usage, such as a push bike conversion. I'll see.
Qty price is less than $20 per cell, but again, there are no tabs exposed at all.
He shows examples of having peeled back on the envelope and attaching an eyelet terminal.
Should be ok for lower current usage, such as a push bike conversion. I'll see.
Qty price is less than $20 per cell, but again, there are no tabs exposed at all.
miro13car
100 kW
webfootguy,
thank you for your in depth opinion.
I was wondering why those tabs were so strangly scarred/mingled , now I think they were maybe crimped or clamped in the pack. In at least 5 pictures in various web sites I never saw tabs of A123 flat cells like that, all pictures show smooth tabs , maybe shorten but smooth surface of tabs.
He says cells are new. Go figure.
If it comes to specs he provides , they say Ir less than 1 miliOhm.
Just open the file/picture next to pictures of cell.
Go figure again, so what should I believe as factory specs?
MC
thank you for your in depth opinion.
I was wondering why those tabs were so strangly scarred/mingled , now I think they were maybe crimped or clamped in the pack. In at least 5 pictures in various web sites I never saw tabs of A123 flat cells like that, all pictures show smooth tabs , maybe shorten but smooth surface of tabs.
He says cells are new. Go figure.
If it comes to specs he provides , they say Ir less than 1 miliOhm.
Just open the file/picture next to pictures of cell.
Go figure again, so what should I believe as factory specs?
MC
olaf-lampe
10 kW
Regarding the Ir measurment: maybe the Ir-meter assumes to test a 12v battery and therefor the Ir is shown roughly 4 times lower than regular?
-Olaf
-Olaf
lesdit
100 W
Regarding these 'leaked' or 'back door' 20ah cells, are there any data sheets as well? I want to make sure that I charge them safely, etc.
I don't feel extrapolating from other a123 product is right.
I don't feel extrapolating from other a123 product is right.
webfootguy
100 W
The only place I have seen anything official looking is here: http://mavizen.com/A123.html
Specifications: 20 Ah Cell Specification:
--------------------------------------
Normal Voltage: 3.3V
Capacity (1C to Vmin=2.0V): minimum 18.5AH, typical 20Ah
Whr/Cell: 64.6
Dimensions(mm):7.2 x 161 x 227
Weight (kg): 0.495
Volume (l): 0.263
Operating Temperature: -30c to 55C
Storage temperature: -40C to 60C
Number of Cycles : minimum 300, typical 2000
Max Discharge (SOC and Temp dependent): 300Amps
Max Charge (SOC and Temp dependent): 300Amps
Wh/kg: 130.5
Wh/Liter: 245.6
Self Discharge @ 25C: <2%/month
Dimensions (mm) 7.25 x 160 x 227
Weight (g) 496
Nominal Voltage and maximal / minimal discharge voltage (recommended and critical) 3.3 nom, 3.6 max, 4.0 critical. 2.0V min, 1.0V critical
Nominal Capacity: 18.5Ah min, 19.6ah nom
Internal resistance: 2 mOhm nom
Specific Power (nominal, W/kg): 2400
Specific Energy (nominal, Wh/kg): 131
Maximal current discharge rate: 300A cont, 750 peak
Charge conditions: maximum voltage, charge current CC-CV to 3.6V. 300A max, 600 peak
Cycle life: Min 300 cycles, typ 2000
lesdit
100 W
Thanks,
I also read somewhere that a peak charge voltage of 3.5 and a low of 2.5 will keep a123 cells comfortable. I hope this is true for the 20ah version, not just the cylindricals.
I also read somewhere that a peak charge voltage of 3.5 and a low of 2.5 will keep a123 cells comfortable. I hope this is true for the 20ah version, not just the cylindricals.
jimw1960
10 kW
I charge mine to 3.65 and they quickly come to rest around 3.55 after removing the charger.
miro13car
100 kW
webfootguy,
thanks for specs,
but
EVfalcon specs says clearly Iresistance nom 0.5mOhm?????
MCM
thanks for specs,
but
EVfalcon specs says clearly Iresistance nom 0.5mOhm?????
MCM
Then from what I've seen of these cells either they're lying or they're measuring them in a very different way (DC and AC IR tests result in very different numbers...though I don't remember atm which way the numbers skew).miro13car said:
frodus
10 kW
miro13car said:
[sarcasm] I've NEVER heard of a distributor skewing specs on a product.... Mavizen MUST be wrong [/sarcasm]
Wait a minute, does FalconEV have a contract with A123? ooops, didn't think so. I'd trust the specs from a company that actually has a legitimate contract with A123, over a distributor with somewhat of a reputation for misinformation.
Why doesn't FalconEV post on this forum anymore? Does anyone know? hehehe
miro13car
100 kW
frodus,
I must agree with what you say, BUT
did anybody buy any cell from Mavizen??
At A123RC they run out of 20Ah cells.
Cellman doesn't have any.
I must agree with what you say, BUT
did anybody buy any cell from Mavizen??
At A123RC they run out of 20Ah cells.
Cellman doesn't have any.
frodus
10 kW
yeah, actually they did. Crodriver bought 1000 of them from Mavizen.
http://www.diyelectriccar.com/forums/showthread.php/new-source-a123-cells-58298.html
http://www.diyelectriccar.com/forums/showthread.php/new-source-a123-cells-58298.html
jimw1960
10 kW
curious said:Anyone willing to contribute some personal time and arrange a small group buy from Mavizen ?. I need at least 25, perhaps 40-50 pcs.
Isn't Mavizen located in the UK? That would make shipping charges pretty high and after buying cells from China, I sick of all the hassles of dealing with customs. They're still bugging me for paperwork from 30 cells that I bought over two months ago. Why can't a US company like A123 have a single reliable retail outlet in their own damn country. Sorry for the rant.
OMG! Now we have our own customs that want to give us hard time. Perhaps it is time to move to some reasonably civilized SE Asia place. I kind of like the food there (except insects, dogs and cats :? ).jimw1960 said:
I know that A123 had some patent issues that restricted them from selling products in US but I do not know the details and how this was resolved. Lack of official US distributors is extremely frustrating. And it looks like a start of a dangerous trend...
wojtek
100 kW
jimw1960 said:curious said:Anyone willing to contribute some personal time and arrange a small group buy from Mavizen ?
Isn't Mavizen located in the UK? That would make shipping charges pretty high and after buying cells from China, I sick of all the hassles of dealing with customs. They're still bugging me for paperwork from 30 cells that I bought over two months ago. Why can't a US company like A123 have a single reliable retail outlet in their own damn country. Sorry for the rant.
Mavizen Limited, Noble House, Mount Hill Lane, Gerrards Cross, Bucks, SL9 8SU United Kingdom
999zip999
100 TW
Yea I only eat American cat and dog at the local Aasian resturant.
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