Are this A123 real or fake?

The pictures look to be from real A123 cells, but notice the existing spot welds on the lower pictures ( removed from used packs ) , same seller also has in his store :

http://cgi.ebay.com/LiFePO4-48V-15AH-BATTERY-FOR-ELECTRIC-SCOTTER-E-BIKE_W0QQitemZ370215474258QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item56328fd452&_trksid=p3911.c0.m14&_trkparms=65%3A12%7C66%3A2%7C39%3A1%7C72%3A1205%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

.. IF the cells you get are Real A123's and they arrive with good voltages, not bad. but if you order and get the duct tape box with 18650 cells in it... not so good..

edit : checked the other 3 links, those look more credible imo.. so yeah.. looks right other than the 1st one i'm a bit worried about.
 
Get nearly unlimited Dewalt packs for free, dismantle the batteries, discard the 1-2 cells that failed, pass on the remaining good cells to us for a great price.

Kinda like a Chinese version of our Doc.

There is also a supply of brand new never been tab welded M1 cells from the giant A123 stock sell-off after they got rejected for the Chevy volt project. You can find lots of 1,000 brand new still factory sealed packaging cells for ~$5,000usd.

It's interesting that it seems A123 sold the excess inventory ONLY to Asia. :( :x
 
the last one says, that this are brand new cell direct from dewalt factory...his price is 6,3$/cell including shipping...

yes, two say, that they have used cells...

where can i get used dewalt pacs for free... :D ??
 
ypedal, I bought a 48/15 pack from olympics2000888. It weighs 15lbs and works fine. It's too light to be 18650 cells.
 
Tomorrow will be 4weeks and I still didn't get batterys from this ebay seller. I paid 110$ for shipping and still didn't have it. :( It is to much of waiting for them.
 
I bought the pack on April 15. didn't receive it until May 1st. It took them 2 or 3 days to ship it, but the other 2 weeks
were spent on something else. This vendor wouldn't answer any emails after I made purchase.
If you're going to buy from foreigners a common problem seems to be poor communication or playing opposum.
 
i got 16 cells from olympics2000888 and they are good. i have only tested them to 24amps 10C and the voltage sags down to 47V so may be they are old cells or maybe my spot welds are soaking up volts. i am happy so far i will post again when i have some miles on them.
 
how deep can A123s cells be discharged?

Can it go deeper than 80% or better not going under 80%DOD?
 
I don't know how far down you can go. I rode 15 miles on a Aotema brushless kit and the
pack still had 52v. I'm refering to my 48v 15ah pack from olympics2000888.
It's not a good idea to go deep with most kinds of batteries. Has anyone opened up an olympics pack?
Originally, I thought he was using either pouched cells or A123's. The pack is too light/small to be 18650 type or the like.
So far no problems.
 
The latest information I have is that a 18650 A123 cell with a clearly visible black pen mark under the heatshrink, on the stainless-steel body, is an old or rejected cell.

It may well be rejected or old...........but A123 is still A123, of course.

My proof?

Two fold.

First, this:-

http://cgi.ebay.ie/ws/eBayISAPI.dll?ViewItem&item=200508152121&ssPageName=STRK:MEWAX:IT

EBAY VENDOR said:
Important Note:

We promise we sell original and new A123 SYSTEM'S 18650 Cells.

But we are not allowed to provide original packaging. Our packaging is just like in the item picture.

packaging is not a factor to judge if the A123 18650 is original or not. Please note this fact:

Only A123 systems' lifepo4 batteries can reach 30C constant current and 60C peak current.

Other lifepo4 batteries can't reach this high standard!

The sole standard to judge if the battery is original A123 battery is the current rate!!

The key to pick good original A123 18650 is to test the voltage, capacity and internal impedance.

We promise each cell is picked very strictly to ensure the performance.

We want to introduce some bad batteries for your reference. These batteries are with bad quality.

You can see there is an ink mark inside the yellow cover, on the battery metal body.

18650-dcjs2.jpg

18650-dcjs3.jpg




The second part of my proof is this: I have been buying these batteries and have come across, quite often, the same black mark that the above vendor/seller speaks of.
However, I then received a shipment of these cells which featured not one but TWO layers of heatshrink/plastic. This gave the battery a very new, very shiny exterior.
Peeling off one layer....hey presto, the black mark becomes visible again under the next layer.

So it's obvious something is afoot. The guys selling this old/rejected stuff know that the above seller has put the word out and are now covering their tracks.

Personally, I have reason to believe that the VPower and Cammy packs are made from rejected A123 cells. I know that my 36v 20Ah battery was a heavy mother that could easily put out 29Amps- which is all the controller could handle. If you look at the Cammy that one user had an issue with and pulled the wrapping off, you can see those tell-tale bright yellow stickers.
 
Also, can anyone prescribe a quick test for measuring impedance and/or resistance, plus their discharge rate? Anything simple and home-made, I am not looking for exact figures, merely a sort of yes-or-no test.

THANKS! :D :D
 
The Mighty Volt said:
Also, can anyone prescribe a quick test for measuring impedance and/or resistance, plus their discharge rate? Anything simple and home-made, I am not looking for exact figures, merely a sort of yes-or-no test.

THANKS! :D :D

These cells are 1.1Ah rated and are used in the 18V dewalt nano packs.

These pack have 12 of them in 6s2p.

They are 18650 format ( same as konion)

Their C rate is the same as the 26650 M1 2.3Ah cells

so that give 30A continuous and 60A burst for 10 sec.

The Effective DC internal resistance @ 50% SOC ranged from 36-39 mohm.
 
ça va Doc ?

Yes....I know this information already, but how do I test a cell I have, to see if it comes close to these figures? Just even a home-made test for resistance/C rate.

Thanks!
 
The Mighty Volt said:
ça va Doc ?

Yes....I know this information already, but how do I test a cell I have, to see if it comes close to these figures? Just even a home-made test for resistance/C rate.

Thanks!

to barely measure RI you need two differnet load for the cell you want to measure.

You just need to draw let say 1A using a resistor of 5W

and then draw 10A with another resistor and measure the voltage of the cells while connected to these load.

( yo can chosse your own resistor valur for sure .. just ensure it's at least 5 or 10 time different)

then knowing the two voltage you measure substract the highest with the lowest and divide that value by the amp difference you had.. ex:

measured 1:

measured current: 1A
voltage was 3.56V


measure 2:

measured current: 10A
voltage nmeasured: 3.44V


now you do the math:

(3.56 - 3.44) / (10 - 1)

= 0.12 / 9

= 0.013

The measured Ri is 13 miliohm.


The best is to measure RI at 50% soc.. but you can decide also to know the RI at the SOC you desire....


Doc
 
You need a good voltmeter (ideally at least 3 decimal places... I use 7.5 digit HP 3457A's) and a known load resistance. A lamp is NOT a valid load resistance. It varies wildly with voltage/temperature/etc. You never know what its resistance is. Even those rectangular ceramic "sand" power resistors are terrible loads (I found that out when I used them as a load on my CD tab welder that I added a CBA type cell analyzer mode to... their resistance can vary well over 20 percent with even moderate self heating). I have found those Dale "gold" aluminum cased power resistors to be very stable with temperature. This test does not depend on knowing the test current, just the load resistance and cell voltage. Note that Rload should include the resistance of the leads to the cell.


Ok now to the test:

Ideally you want a load resistor that will load the cell to around at least 1C. Connect the load resistor to the battery. Give it some time to drain off the surface charge of the cell (monitor the voltage at the cell and when it somewhat stabilizes). Measure the voltage AT THE CELL. Call this Vload. Remove the load and quickly measure the cell voltage. Call this Vcell. Calculate Vdrop = Vcell-Vload. The cell Ir = (Vdrop * Rload) / (Vcell - Vdrop)
 
Have bought some of the A123 18650 cells from ebay, first tried to discharge them with 3A instantly the voltage sag under 2 volts, then tried with 1A discharge and got approx 1AH capacity, so no way they are from A123, just regular cheap chinese LIFEPO4 cells
 
@Doc and Texaspyro: Thanks a lot for your help, I plan to do that soon! I will post the results here for the so-called A123 cells and compare them with a cell I know to be A123. I just need to get some resistors now for the job.

@Artoz: that doesn't surprise me. What does surprise me is why don't they just sell them as cheap LiFePo4?? Why bother with the pretense? Most people will happily pay $1 for a cheap LiFePo4 battery anyways.

Regards
TMV
 
texaspyro said:
This test does not depend on knowing the test current, just the load resistance and cell voltage. Note that Rload should include the resistance of the leads to the cell.


Ok now to the test:

Ideally you want a load resistor that will load the cell to around at least 1C. Connect the load resistor to the battery. Give it some time to drain off the surface charge of the cell (monitor the voltage at the cell and when it somewhat stabilizes). Measure the voltage AT THE CELL. Call this Vload. Remove the load and quickly measure the cell voltage. Call this Vcell. Calculate Vdrop = Vcell-Vload. The cell Ir = (Vdrop * Rload) / (Vcell - Vdrop)





Thanks for some added details, I did now specified everything since there is a lot of other thread where I spoke about that with more clarifications.

But there is just some of them I disagree with.

It was proven that DC internal resistance measurement are more precise when doing measurement at TWO different load level than just one load level compared with the no load voltage.

Read on the Battery University, Sandra lab website and A123 technical literature, etc

The problem with single load level is HOW can you ensure that the time you wait for the no load V measurement is the best delay?.. 5 sec, 30 sec, 1 minutes.. etc… The voltage vary in time and increase when you release the load… that add inaccuracy in the measurement.

I have both Ri meter type and the two level load give a lot more accurate and repeatable measurement results.

I was surprised to see that many single load level Ri meter on the market use DIFFERENT time delay for the no load measurement!!!.. How can you ensure wich is good?.. 2 sec?, 15 sec etc… since the voltage you measure is influenced by that determined delay !


The load resistance value is not really important.. it’s the measured current and the corresponding voltage at the cell tab.

You can have a 1 ohm, or a 1.21 ohm etc.. the resistor precision is useless… you only need to draw a current to the cell that is in an appropriate range for the RI measurement. So by measuring just the current you don’t need to care with the resistance loss of the wiring, contact etc…..

For sure the resistor wattage MUST be appropriate and being at least 3 times higher than the power you will draw. To ensure is stay in the spec range

Ex: lifepo4 cell measured first with a 1.1 ohm resistor :… and you measure 2.8A and 3.400V..

That mean your total load resistance is 3.400 / 2.8 = 1.214 ohm…… including every wiring and loss ( you don’t need to care about the real ohm of the resistor !!).. just take the current and corresponding voltage value!

Repeat that two times with a different load and do the math.

Yes The Ri at known C rate is important… but the most important is to know the RI at the C rate YOU will use your battery !

This is the spec you will use… This is what you need to know.


Unless you do some opensource battery test and want to compare with the manufacture official specs.

Doc
 
I built a nice cell test fixture using an HP3457A 7.5 digit multimeter and GPIB conttroller. It has three load resistors it can switch in to do Ir measurements at three currents. It can measure Ir down to a micro ohm or so. It does 4-wire resistance measurements so I can easily measure the load+wire+relay+contact resistance for the calculations. Otherwise use a good resistor and heavy contact wires and live with the inaccuracy.

For most people doing casual testing the single load resistor test using a voltmeter works pretty well and can be done manually. Testing at around a 1C load is OK and does not tend to cause too much heating in the load and usually causes enough of a voltage drop to be easily measurable. Testing at the load current that you will be using is a better idea, but can be quite a bit more difficult.

I connect the voltmeter directly to the cell (It must not be at the ends of the wires at across the load), apply the load resistor until the voltage stabilizes (it will always be falling, but should stabilize somewhat). Then, while looking at the meter remove the load and check what the voltage pops up to. It will keep rising, but the value you want is the first full meter reading cycle after removing the load.
 
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