A123 Cells and a soldered pack

[cell_man]

There seems to be much discussion about fake A123 cells going around so I thought I'd add to the confusion

I have bought a batch of ANR26650M1 2.3Ah cells. I previously sourced some samples from some from some other sources, from Shenzhen and HK. The supplier I will be going with is from another location in China which I will not be disclosing Anyway, I've had a look at the cells I have received and underneath the wrapper they seem to be identical. Here's a pic of a cell I unwrapped:

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It's not easy to make out, but if you look carefully at the 2nd and 3rd pics you should see "A123 Systems" laser etched into the case above the serial number which includes the date of manufacture. This mark has been etched over for some reason so it is not easy to see in the picture but easy enough in the flesh. You can see the case has ends made of a different material from the main body. The main body is non magnetic and appears to be aluminium. The negative end is a small button sized disk which is highly magnetic which is surrounded by a plastic ring which isolated the positive and negative polarities. Below is a picture of the cell with the disk removed. I've already soldered the cell in the picture, ordinarily it has a shiny finish and is quite easy to solder onto. The button in the middle is negative, whilst the ring around it and the entire case is positive. The positive end of the cell has what appears to be a thin disk of some mildly magnetic material bonded in some way to the end piece. The end section is not magnetic, only the thin disk bonded onto it. I would hazard a guess to say that this is to make the job of spot welding the cells a bit easier (it also happens to make soldering them possible as well). It has been stated that these cells are not easy to spot weld, but I have seen thick Nickel tabs spot welded to them using a fairly inexpensive, but quite powerful spot welder. Spot welding copper is a whole other ball game and does require a higher power machine, but I am assured that it can be done by manufacturers of higher spec machines. It remains to be seen the actual improvement in performance copper sheet offers when compared with correctly sized Nickel type tabs.

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None of the cells I received were in shrink wrap that are supposed to signify a non "pirated" cell and many would say they are fake, because that is what a leaked document from the Authorised Retailer has stated. As you can see, the cells I have been playing with would appear to be A123 manufactured cells. The cells I will be supplying in the future do not have A123 Systems on the heat shrink label but do have the Part No. ANR26650M1 on the heat shrink and underneath can be clearly seen, a serial number which includes a date of manufacture, typically 1 year previously or a little less. I have tested a few cells and they have about the correct capacity of 2.3Ah. I've also done some very rough and ready load testing with some power resistors and was able to pull 70 or 80A from a single cell whilst still maintaining a reasonable voltage for LiFePO4 which is being hit hard, of about 2.5V. I put pretty much a dead short across the same cell and was able to get over 250A but terminal voltage was way down at about 1V, so I'm not suggesting this is usable.

I've looked into independent tests of A123 cells and they generally suggest that the spec stated by A123 is a bit optimistic. For reasonable life cycle, the 30C constant rating is likely to end in a premature demise. Anyway I will pull up some of these documents for anyone that is interested when I have a minute. My feeling from the rough and ready tests I've done so far suggest that the cells I have are similar in performance to what independent tests have produced. I suspect the cells I have are not quite as low an IR as cells bought from Enerland or A123 Racing, but they will be much cheaper.

Until I've sourced a spot welder, I was desperate to get some thing put together to have a play. I wanted a pack that would fit with in the triangle of my full suspension bike and decided upon 16S, 4P as that is what I had ordered from a different supplier (I will not be supplying the cells shown in the build below). The cells are linked with 0.2mm copper sheet and are soldered using a 200W iron set to 500degC. I was very careful to minimise the time the iron was in contact with the cells and I'm getting the hang of doing the termination without causing the cells to get overly hot. Cell logs are gonna be used for LVC. Will post some more details later if there's interest. Gotta get off as I need to meet someone. Here's some pics of the rather rough pack I've been playing with:

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[cell_man]

Even though there seems to be no love for anything battery related that isn't HC Lipo these days around these way I thought I'd give you all a bit more info I've gathered on some of the A123 cells available here in China

I just wanted to say, that pack above is just something I was playing with and I wouldn't sell anything looking so rough The cells are some that I bought from a source here in China and they all appear to be genuine with A123 Systems etched into the case under the heatshrink and in this case there has been no attempt to cover the logo as per my above picture of a cell from another source.

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The only issue I had with these cells was that they were dated from 2007 and 2008 and they just didn't look pristine when I received them. There was signs of some oxidization on some cells with some having some small dents. These cells had just 1 layer of Heat Shrink and has all the right markings except the serial number on the outer packaging, but like I said these are 2 years old plus, so not sure what the situation was with regards to packaging at that time. From what I can gather the cells now generally available in China dated 2009 (cells are not released until almost 1 year after manufacture I've been told) seem to have the logo etched over. I've been assured the cells are A grade cells but I will be making every effort to confirm this by getting all cells independently tested. I have my doubts about cells available with manufacturing dates of 2 years ago plus and have heard stories from people in the know of cells that were supposed to be recycled getting back into the food chain as it were. I've been told the cylindrical A123 cells are primarily manufactured in China, including the larger format 32113 which will be available as High Energy and High Power versions for EV and hybrids. Some independent checks seem to confirm what I've been told, that pouch cells primarily originate in Korea and Cylindrical cells from China.

This week I'll be visiting a testing facility to get the cells I've recently purchased independently checked and visiting a pack assembly factory, so will try to get some pics and post up some info.

I'm not into making false claims and the folks here on ES wouldn't be long finding you out and dishing the dirt, so honesty is the best policy in my book I sold pretty large numbers of pouch cells and there were no serious issues from any customers, the odd small issue was resolved amicably, so I think I've proved myself to be trustworthy

If anyone has any ideas on pack layouts that would work for them or sub packs that could be easily DIYed into bigger packs without special tools, please post up your ideas. I'm all ears and will do what I can to oblige

 

[bzhwindtalker]

I love them
the price will be in what range for raw cells? comparable to lipo nowdays?
if each cell do 50a with reasonable sag and great price, you could start to make some triangle packs for ofroad bikes, 12s4P and 16s4P should sell great if they are cheaper than lipo?


Adam

 

[docnjoj]

That is a right pretty soldering job. Cell_man! Those high wattage irons and some skill really do the job. I hope these cells can become readily availible as I have considered Lipo for my next pack but it seems too "fussy" with all the stuff you need to keep it safe. Good luck on your venture!
otherDoc

 

[amberwolf]

If anyone has any ideas on pack layouts that would work for them or sub packs that could be easily DIYed into bigger packs without special tools, please post up your ideas. I'm all ears and will do what I can to oblige

Since RC Lipo packs are so commonly used, why not emulate that method and make A123 packs in as similar a form-factor as possible, with the same balance connectors (but thicker wires :lol?

Then people that have Lipo setups with adjustable-voltage LVC/HVC equipment could change to A123 if they wished, and/or some existing BMS or balance systems (like the Fechter/Goodrum systems) could be used along with your packs.

 

[cell_man]

Thanks guys for the comments

I love them
the price will be in what range for raw cells? comparable to lipo nowdays?
if each cell do 50a with reasonable sag and great price, you could start to make some triangle packs for ofroad bikes, 12s4P and 16s4P should sell great if they are cheaper than lipo?

Adam

Adam,

I'm still trying to figure out an exact price as I'm still working on how the packs will be offered, total cost of additional testing and additional material. I will try to do my best, but there's only so far I can go. All the cells will be tested, matched and put together into a pack for a very competitive price. For sure a triangle pack is on the cards and I wish I didn't stick the above pack together quite so well. That glue is too damn strong.

That is a right pretty soldering job. Cell_man! Those high wattage irons and some skill really do the job. I hope these cells can become readily availible as I have considered Lipo for my next pack but it seems too "fussy" with all the stuff you need to keep it safe. Good luck on your venture!
otherDoc

Thanks Doc looking back at the pics I think it looks terribly rough, but I just had the cells sat around and thought I'd give it a go until I have a spot welder. I've since found out the disk on the positive end of the cell is a sheet of Nickel 200 and the negative tab is nickel plated steel. When it comes time to source your new pack I would hope to have something that works for you.

If anyone has any ideas on pack layouts that would work for them or sub packs that could be easily DIYed into bigger packs without special tools, please post up your ideas. I'm all ears and will do what I can to oblige

Since RC Lipo packs are so commonly used, why not emulate that method and make A123 packs in as similar a form-factor as possible, with the same balance connectors (but thicker wires :lol?

Then people that have Lipo setups with adjustable-voltage LVC/HVC equipment could change to A123 if they wished, and/or some existing BMS or balance systems (like the Fechter/Goodrum systems) could be used along with your packs.

Agreed, the balance wires are very thin. I bought some pre terminated ribbon cables with the correct pins, so they are very handy, but they're only available in that very small size. It's ok for a cell log or a conventional BMS, but not much more. I'll use the appropriate sized cabling for the application, or as big as I can fit in the connector

It will take a little time but I do hope to have some different form factors that work for different people and at least initially will be happy to offer packs built to order for no additional charge until I have established some standard products. I'm really going to have to broaden my horizons a bit wider if I'm going to be successful with these cells as it seems most on ES can't see beyond LiPos charms.

The last couple of days I've been getting some cells tested and was pleasantly surprised by a few things. Here's me testing the internal resistance of a cell:

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I was quite happy to find that the cells all had very respectable IR between approximately 6 and 8mohm, with the spec sheet stating 8mohm. I've now ordered my own IR tester and will be checking every cell prior to packing.

All the cells I've ordered for the initial order will be tested and grouped with max variation of 25mA within groups. Cell capacity is typically 2200mAh to over 2300mAh on the cells tested so far. The machine below can test over 250 cells at 1 time. All the cells that are shown in the pic below are duplicated on the rear of the unit. It still takes a long time to get the cells tested, even with this kind of equipment.

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The more I've tested these cells and the more I found out about the supplier and the supply chain, the more confident I am of the quality of these cells These cells are sourced through 100% legitimate means. They are new, pristine and individually tested to confirm performance. I'll try to offer good prices and hope to reduce those prices as I can, but I want people to recognise that these cells are a premium product that can be relied upon.

 

[boostjuice]

WoW! Battery testing Pron. Did you buy that equipment or is it on loan? These pictures should stop Armin flapping his gums about cell fakery

I had a go at soldering some S/H A123 26650 cells myself but i just hated the amount of heat i put into them and the mess i made (even though i was using one of these to minimize heating duration. If you can make a professional looking triangular pack to fit in a pre-specified triangular area using tab welded termination i would be very interested.

 

[cell_man]

WoW! Battery testing Pron. Did you buy that equipment or is it on loan? These pictures should stop Armin flapping his gums about cell fakery

I had a go at soldering some S/H A123 26650 cells myself but i just hated the amount of heat i put into them and the mess i made (even though i was using one of these to minimize heating duration. If you can make a professional looking triangular pack to fit in a pre-specified triangular area using tab welded termination i would be very interested.

For sure, you need a big old soldering iron to wet the positive end, negative isn't so bad. I've got spot welding recommendations from A123 and it is recommended that when soldering onto the nickel joining the cells, the cell ends must not exceed 150degC for a max of 5s. Of course you are not supposed to solder directly, although I think you can get away with it. A combination of a big 200W iron, set to 500degC, abrading the cell before commencing, applying additional flux and keeping each stage to the shortest possible time seem to work out ok for me, but having said all that, it's a damn site easier and quicker to spot weld a pack that it is to solder.

At the moment I'm paying a company to do the testing for me in addition to the cell costs. I want to start getting some more equipment but no point rushing into it. At the price I'm paying for testing, I'd be a long time paying off for the test equipment, even if I ignored the work required to do the testing and run the equipment. Will be looking into a suitable spot welding machine ASAP. I really need to find some nice enclosures as well, so much to do. Will have to stop myself from spending so much time on the computer, it just eats up your day.

I definitely hear you on the triangle pack. The type shown on ebike.ca is probably the most effcient use of the available space for a frame mounted pack, but with the cells being 65mm long, the pack could be a bit bulky if 2 across end to end. That was why I went with the way I did above with 4 side by side. Drop me a line if you are serious about putting a triangular pack together and I'll see what I can do

 

[texaspyro]

I've got spot welding recommendations from A123

Can you share any of those? I have built my own FET based spot welder (see http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=582 and http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&p=282544&hilit=spot.jpg#p282544) and would love to know what they recommend.

For that matter, if anybody has any, I would love to get my hands on a few dead A123 cells to torture.

 

[texaspyro]

I've got spot welding recommendations from A123

Can you share any of those? I have built my own FET based spot welder that can run rings around $20,000+ commercial units (see http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=582 and http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&p=282544&hilit=spot.jpg#p282544) and would love to know what they recommend.

For that matter, if anybody has any, I would love to get my hands on a few dead A123 cells to torture.

 

[cell_man]

It's getting a bit late here. I'll dig out the sheet and post some info tomorrow. Give me a nudge if I forget

 

[richmpdx]

The possibility of having a source for quality A123 cells/packs is quite appealing. While the HC lipo packs have some advantages, the properties and long life of A123 LiFeP04 cells still makes them desirable to many. Either fully assembled packs with BMS or even 4P or 5P or other sized units that could be assembled by the purchaser into custom packs would be great. The structural stability of the welds/units is crucial, there have been many problems with broken connections/welds for packs made out of lots of small cells. In any case, looking forward to hearing more about this.

Rich

 

[cell_man]

The possibility of having a source for quality A123 cells/packs is quite appealing. While the HC lipo packs have some advantages, the properties and long life of A123 LiFeP04 cells still makes them desirable to many. Either fully assembled packs with BMS or even 4P or 5P or other sized units that could be assembled by the purchaser into custom packs would be great. The structural stability of the welds/units is crucial, there have been many problems with broken connections/welds for packs made out of lots of small cells. In any case, looking forward to hearing more about this.

Rich

Thanks Rich. Yes I agree that there is definitely still a place for quality A123 cells and packs. For sure the terminations need to be made properly, but I am sure that if the correct spot welding machine is used with the correct thickness of termination material, the connections will be very robust. I've also been using some high temperature hot melt glue and that stuff is strong.

 

[cell_man]

The welding recommendations/guidelines include and are likely required due to the quite thick nictel tabs that are generally used:

Pressure: 7kg force per electrode
Squeeze: 250ms
Weld Time: 5ms
Weld Power: 5kA
Hold: 250ms

Positive terminal is 0.2mm Ni-200 laminated to 1.0mm Aluminium
Negative terminal is 0.8mm Nickel plated steel

When soldering leads onto the cell, the terminals must be kept below 150degC and soldering must take no more than 5 seconds.

The cells vent from the positive end cap and not the negative as it would appear by looking at the negative terminal. At least 1mm gap at the cell end is recommended to allow the cells to vent. No more than 40lbs of force axially down on the terminals.

The recommended welders are Miyachi Unitech models.

 

[MitchJi]

Hi Paul,

When soldering leads onto the cell, the terminals must be kept below 150degC and soldering must take no more than 5 seconds.

An earlier post stated or implied (I forget) that soldering is only recommended for the tabs, not the cell. Which is correct?

 

[cell_man]

Hi Mitch,

the guidelines state:

"All welding guidelines must be followed when attaching tabs or leads. If soldering leads on the cell, the cell terminals must be kept below 150degC, and soldering must take no more than 5 seconds"

I think this could be interpreted in different ways. I only received this info the last couple of days. My personal feeling for what it's worth is that it's possible to solder a connection without heating the cell excessively but it takes the right tools and technique. I was thinking about buying a resistive soldering iron, as they claim to introduce much less heat into the part being soldered, but they are expensive and the process will be slow. For now, I'm thinking a good quality Spot Welder is the best tool for the job.

 

[liveforphysics]

Mitch- Any cell can be soldered and not be damaged if done correctly. Takes a very powerful iron, good prep, and some skills.

Mfg's like to always discourage soldering cells because if you don't know wtf you're doing, you can wreck your cells. Cell soldering isn't for clowns.

 

[Karolis]

Bought 100W iron for 6$, made my own flux from small percentage HCl and AAA battery's body which contain Zn A flux left a little bit acid, because iron tip was eaten after 80pcs of cells soldering, (ofcourse iron tempereture helped a lot in that eaten proces) but bought new iron tip for something like 0,7$ and soldered all 100pcs to the end. Tried original Weller acid flux "ZnCl" and it didn't worked as mine. With 100W iron it was pretty easy, because after 5s of soldering process you could touch your face with soldered place of the cell and it felt like it was only warm. For cell interconnection used desoldering braid 4mm http://www.rcl.lt/index.php?id=2&lang=en&begin=12&acc=show&fid=507&pcode=ILYDS5&pmode=&frame=3

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[cell_man]

Hi Karolis,

have you got any more pics of the completed pack? The way you've done it looks pretty effective. There's just 1 thing you've done that was unnecessary. If you look at my previous post:

"The cells vent from the positive end cap and not the negative as it would appear by looking at the negative terminal. At least 1mm gap at the cell end is recommended to allow the cells to vent."

So there is no need to leave a hole for that little thing that looks like a vent on the negative terminal, it's not. The cells vent by splitting on the positive end, so you need to ensure the cells have enough space to split. The standard spot welded terminals used in the fat packs add to the confusion as they appear to allow a space for the centre of the cell to vent. That is not the purpose of the design :wink:

 

[Karolis]

Yeah, I know that they went through negative. I Didn't make more photos. But configuration is 2 pack of 8s5p and one 4s5p.