How much is getting tested & matched A123 20ah cells worth?

I just heard back from Nancy at OSN Power. The price of their A123 cells with full tabs went up to $35 each for the "A grade" cells. She also said they are running low on this inventory.

Does this mean that the supply of first quality A123 cells made in the USA is finally drying up?

Also, does the factory in Korea only make cells with short tabs? Anyone know what the tabs lengths are? These tab lengths are shorter than the full tabs but how do they compare with the cut tabs on the salvaged cells with holes in them?
 
RayGo said:
Also, does the factory in Korea only make cells with short tabs? Anyone know what the tabs lengths are? These tab lengths are shorter than the full tabs but how do they compare with the cut tabs on the salvaged cells with holes in them?
Click to expand...
Tabs are short not by manufacture, but salvage as they are cut out of bonded battery packs. No one knows when the supply will dry up. Could be happening, or it could be years. If you want an A123 AMP20 pack on the cheap, play it on the safe side and buy your cells now.
 
Hi Luke,
liveforphysics said:
With respect to the NMC cells, the for sure the best cells in the world right now use NMC, but that doesn't mean because it's NMC it will be amazing automatically. The chemistry alone determines maybe <30% of a cells characteristics (safety, cycle-life, calendar life, C-rate, etc). The other 70% of how that cell is going to perform is up to folks designing the cell (a very big factor simply being the quality of the solvent used). What I'm saying is, you can have some really doggy NMC cells with crap life and bad sag and crap, OR, you can have amazing NMC cells with crazy energy density and 10,000cycles and awesome safety etc. Hopefully these are leaning more towards awesome than sketchy, but don't automatically assume just because it's NMC based that it's automatically going to kick-ass until you test them.
Click to expand...
If the 20C cells are really 20C isn't that a pretty good indication the cells are pretty good?
 
20c at what voltage sag? How many cycles do they actually last if you put them thru that alot? Those are two other questions that would matter to say fi they are "good", relative to other NMC.

Another question that would be important is what happens hwne you abuse the cells, such as overdischarge or overcharge. Ideally that would never be allowed to happen, but in our world here on ES, we know it will. ;) Liveforphysics can probably tell us how the EIG NMC used in the Zero fares under such conditions, and possibly other types he may have tested before picking that one.
 
I have only seen the outside of the magic NMC box ( LFP ) and don't know what's inside but think no battery that small and powerful exsits. So must be something else inside. Next I must grab that box and crack it open and realiy take a look.
Free the battery world and made batteries for the people.
What's up with John's NMC's some new new's please ?
My girlfriend still down in Costa Rica but can't get her to spy on him as she went to surf. As a surf nazi on dawn partol.
 
Talked with Victpower last night. They asked me to stop by their factory. It is a long way from Beijing, but I will see if my wife is up to it. It will be 3 months from now though. If any of you ebike business types have specific interests you need researched/visited PM me with the details. A little travel expenses should cover it. As long as there is a train which runs nearby, and I can get it all done in the time I am there. Don't worry, trains are fairly cheap.

Victpower also has a seller/branch in Beijing which I will see about having my cousin stop by. I can do that anytime. I think he can sniff out the nature of things. They sell these batteries in China as well. Of course.

I have this suspicion that if China knows how, and is able to make something useful...they don't just stop to make some guy happy. The balance of power is on technical innovation throughout human history, snivelling lawyers are just the squeeking wheels, and they are really only interested in their own grease.
 
I only got the 4 A123's, so not happy that more of those Korean built cells haven't become available, and that I didn't buy more when I had the chance.

I got the NMC's also, but have yet to get them on a bike which is my only way to load test them.
 
Hi,

999zip999 said:
Are you implying that the made in USA cells have the defect and the korean cells are better ?
Click to expand...
It's not an implication. It's a fact that a bunch of cells made in the U.S., in MI, had a manufacturing defect.
 
999zip999 said:
Are you implying that the made in USA cells have the defect and the korean cells are better ? Remenber USA is your home country.
Click to expand...

The bad machine of the 4 cell making machines in the US factory with no way to distinguish which cells came off of which machine is what led to A123's ultimate demise, though the idiocy of management assured it would never succeed like it should have. The nature of the defect was such that failure could occur at any point, so just like RC Lipo a USA made Amp20 cell can never be trusted.

AFAIK the Korean factory had no such issue, so yeah for me that makes the Korean cells significantly better. Higher than normal self discharge rate or IR, or less than spec capacity, ie the things reasonable to expect of grey market cells is one thing, but an impossible to detect manufacturing defect that results in a catastrophic failure is quite another. It wouldn't matter if cells came from a relative's factory, my opinion would be the same.

It won't stop me from using the USA made Amp20's, but only because my setup is such than my bikes are never inside the house and I charge, store, and use them in locations where a catastrophic failure can't hurt anyone.

John
 
Thanks John i was hoping to get out of your shell. Yes I had a dud out of my 25 @ 40- 60 amps not to hard on this pack ? The USA thing was just to get some talk Thanks good luck.
 
imag0553c.jpg


I did some test with my 28s3p A123 pack from victpower, I believe the IR is a good indicator of how good a pack is, and maybe it says something about the number of cycles too ?
Anyway I have the following numbers.

Unloaded voltage of random cell (3P) = 3.31V and with 105A load it is 3.21V so the Internal Resistance = 0.95mOhm but since it is a 3p Pack it is 2.85 mOhm per cell

A second test at a random cell at the 28s3p pack : unloaded = 3.30V and with 330A load it is 3.00V 2.72mOhm.

can someone confirm if I am doing this the right way ?

And does this still sound like good cells ?

It sounds like they are not performing like new cells, but still good enough to last a few years ? What do others think ?
 
What IR equipment are you using to take measurement?

Am I foolish in assuming a four probe measurement is needed to get a good reading under load.

Doc around?
 
I measured it with a voltmeter directly to the tab and made the load with an amp clamp around a few meters of 10 Awg silicon wire and made a shortcut from tab to tab.
For the 330A measuring I used about 2 meters of 8 Awg silicon wire. Both give me about the same results.
 
:shock: :shock:

2m of 8 gauge shorting a 28s3p A123 pack :?: :?: :shock:

I know i'm crazy but not as far as that!! :mrgreen:

did your 8 gauge wire was in water?... that's serious power!... about 100V and 300A... 30kW in that short wire?.. I am surprized that the wire did not exploded!
Hmm.. unless you did that test to 1s :lol: .. wich make more sense

OK. so for the accuracy of your measurement, what is important is to ensure that the probe location you pick the voltage measurement and also the time you leave it under load.. the delta V is changing while the load is sustained... best is to make it with two different loads and not just one load and open circuit voltage.

2.85 seem to be 4 times higher than what i have measured with my AC RI Hioki meter.. wich would correspond to about 3 times in DC.

I would recheck them and have a probe location far from the load connections and also as close as possible to the original cell tab

best is to apply a 1kW load ( hair dryer, mant 200W bulb in parallel etc) to the 28s pack wich would correspond to about 10-15A load and measure the voltage to every 1s3p cells junction. bt that way you will get the right RI. but youagain, best is to use two different loal devel.. ex: 1kW and 2kW and use the delta V between both and use the delta current between both


Doc
 
No ! Not 2m 8AWG at 100V :mrgreen: That would be insane :shock:

At only one cell I did the test, and I tested a few of them, and all of them were about 2.8 mOhm

I measure at the tab, and about 2 sec with 2m of 10 or 8 AWG, I forgot, and a load of 330A for only about 4 sec.

I want to order more 7s3p from victpower but I want to be sure that these complete packs are still good enough for at least 1000 cycles.

Btw I get about 54 AH out of the 3P pack from 3,65v to a LVC at 2.5v that is still about 18ah per cell.

Any thoughts on this ??
 
Bazaki said:
No ! Not 2m 8AWG at 100V :mrgreen: That would be insane :shock:

At only one cell I did the test, and I tested a few of them, and all of them were about 2.8 mOhm

I measure at the tab, and about 2 sec with 2m of 10 or 8 AWG, I forgot, and a load of 330A for only about 4 sec.

I want to order more 7s3p from victpower but I want to be sure that these complete packs are still good enough for at least 1000 cycles.

Btw I get about 54 AH out of the 3P pack from 3,65v to a LVC at 2.5v that is still about 18ah per cell.

Any thoughts on this ??
Click to expand...


The 54Ah you get is acceptable. The average capacity i got is about 18.7Ah at 100A dishcharge if i remember.

what is really important is to have the voltage sensing of your discharge device to be connected at the right place!.. you must have the sensing wires connected to the cell tab.. in order to get all the mAh measured, you have to ensur ethat the LVC that your dishcarge system is not the voltage at the end of the high current cables otherwise if you have let say 0.1V loss per wire, that's 0.2V lower LVC than the real lvc so the discharge process cut too son and it result that you dont measure all the mAh the cell can do. The diference is minimal but if you are looking for accurate capacity test, i would suhhets to ensure the lvc is properly measured.

In my case i'm using two parallel load tester: the first i sthe CBA III at 10A using 10AWG cables and the main is the CC-400 at 90A with 4AWG cables. The one that snese the right voltage for LVC is the CBA III.

Doc
 
54aha123.jpg


Well, I gave the Icharger 5 cycles with 20A charging and about 5A discharging.
Each cycle was the same and I got 54 Ah in and out. A discharge with 100A would have been better, but then I have no LVC and there is a risk I will forget to disconnect at 2,5V
 
And a discharge curve ( goes to 54ah at a second page )

discharge54ah.JPG


Anything odd ? Or looks like a typical A123 curve ? :wink:
 
looks ok, capacity is specifically measured at .1C so you would have to keep it under 2A to match the spec. i see 10% difference between .1C and .8C on the ping packs and you can add 3-5% from 2.5V(@.3C) to 2.1V(@.1C) as well so i think you are very close to 20Ah, jmho.
 
Are A123 cells available again? Where is the best place to buy them to avoid counterfeits? Seems to be a bit involved to buy this product .. :)
 
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