A123 20Ah Quebec Group buy(Canada) cells ARRIVED 24.57$/cell

[battman]

[If yuo read correctly the A123 documentations you will see that the recomanded temp during charging process is near the ambiant temp.

All from Battery Univercity:
Fast charging of most batteries is limited to a temperature of 5 to 45°C (41 to 113°F); for best results consider narrowing the temperature bandwidth to between 10°C and 30°C (50°F and 86°F). Nickel-based batteries are most forgiving in accepting charge at low temperatures, however, when charging below 5°C (41°F), the ability to recombine oxygen and hydrogen diminishes. If NiCd and NiMH are charged too rapidly, pressure builds up in the cell that will lead to venting. Not only do escaping gases deplete the electrolyte, the hydrogen released is highly flammable. The charge current of all nickel-based batteries should be reduced to 0.1C below freezing.

Thanks. That is generic advice for lithium but you mentioned earlier the A123 documentation indicates a charging temperature "close to ambient". Is "close to ambient" 10°C? The A123 documentation you have that covers charging temperature - if you have it in electronic form could you post it here please? This could be useful information if A123 cells (and the 20AH in particular) have a narrower recommended range than Battery University recommendations.

 

[Doctorbass]

[If yuo read correctly the A123 documentations you will see that the recomanded temp during charging process is near the ambiant temp.

All from Battery Univercity:
Fast charging of most batteries is limited to a temperature of 5 to 45°C (41 to 113°F); for best results consider narrowing the temperature bandwidth to between 10°C and 30°C (50°F and 86°F). Nickel-based batteries are most forgiving in accepting charge at low temperatures, however, when charging below 5°C (41°F), the ability to recombine oxygen and hydrogen diminishes. If NiCd and NiMH are charged too rapidly, pressure builds up in the cell that will lead to venting. Not only do escaping gases deplete the electrolyte, the hydrogen released is highly flammable. The charge current of all nickel-based batteries should be reduced to 0.1C below freezing.

Thanks. That is generic advice for lithium but you mentioned earlier the A123 documentation indicates a charging temperature "close to ambient". Is "close to ambient" 10°C? The A123 documentation you have that covers charging temperature - if you have it in electronic form could you post it here please? This could be useful information if A123 cells (and the 20AH in particular) have a narrower recommended range than Battery University recommendations.

All test done to represent the normal discharge conditions that a123 do are at ambiant: 25 celsius. ( it is on each graph)

DOc

 

[999zip999]

My question about living it on the charger w/bms at always at top charge what it does for longivity of ah.

 

[Doctorbass]

My question about living it on the charger w/bms at always at top charge what it does for longivity of ah.

Leaving any lithium cell at the top cahrge voltage will reduce their life. That's why it is recommanded to cut the charge current when it reach C/20


Doc

 

[battman]

[If yuo read correctly the A123 documentations you will see that the recomanded temp during charging process is near the ambiant temp.

All test done to represent the normal discharge conditions that a123 do are at ambiant: 25 celsius. ( it is on each graph)

DOc

My question was about charging, not discharging. The tests you are referring to may be done at 25 celsius ambient but what is the MINIMUM recommended charging temperature in the A123 documentation you have? Is it 10 celsius like the Battery University website? Is it 25 celsius? Can you just post the documentation here?

 

[pgt400]

Been searching for a good methold to connect & package these cells......as many have bought and many more on the way....any clean, simple, effective ideas?

 

[Doctorbass]

Been searching for a good methold to connect & package these cells......as many have bought and many more on the way....any clean, simple, effective ideas?

That's the next goal.

It will vary alot depending on how much C rate you use. 10C or 20C require alot of surface area from the tab and more pressure against the tab to cary that current.

Lower C rate use will be easyer.. drawing 1 or 2 or even 5C might just require some paperclip to press the cell tab together..

J-L and me are working on that to find our best method for up to 600A use (15C for 2p)

But our main goal is having perfect electrical contact for all cell and having acces to remove one or more cell easy without dissassembling the entire pack. we would like to have the screw to be accessible from the top of teh battery pack not the side

Doc

 

[ohzee]

Yea was discussing this via PM yesterday with someone on the forums who I thought did something quite creative.

if someone could come up with a simple yet effective means to do this I think they would sell like hot cakes.

I know id buy some.

 

[mistercrash]

There's been good discussions on that matter in this thread with examples of what some people did. http://endless-sphere.com/forums/viewtopic.php?f=14&t=36780

 

[oatnet]

Been searching for a good methold to connect & package these cells......as many have bought and many more on the way....any clean, simple, effective ideas?

I am so glad the price has reached a point where these cells are being widely adopted.

I've been spot welding the a123 prisimatics with good success.
Click here for the thread on Spot-Welding the tabs on a123 prisimiatics

Before that in 2010 I was doing a simple 3-fold crimp that pulled 100a from these cells for 90 seconds, without the tab heating up. Both sides of the tabs have a lot of surface area, so compression works great.
Crimping a123 Prisimatic cells

I'll be builiding my next pack 5p or 6p, which means connecting 10 or 12 tabs in a row. I might do something similar to the power takeoffs in my spot-welding thread, but put aluminum spacer blocks between each pair of tabs so they all stay at the same height.

-JD

 

[cassschr1]

I'm gonna try using high density plastic about 7mm thick between each cell by the tabs (160x26x7 mm). Drill 4 holes , one on each side of tab. then use delrin rod 1/4 " thick, cut to length needed, thread the rod, and tighten. Also make rectangle tabs for the balance wires. Hope fully theres a pelican or storm case the correct size. Your thoughts please!

 

[mistercrash]

oatnet, you're crimping method is the cheapest, simplest, most elegant solution I've seen yet. It doesn't ad weight to the pack and it is still possible to change just one cell if need be. I love it.

 

[agniusm]

I will start making this kit for connecting A123 prismatic cells: http://endless-sphere.com/forums/viewtopic.php?f=14&t=38545&p=562221#p562221. It adds some weight to the pack but will make it clean to install with few basic tools and easy to swap cells without the need to use solder.

 

[docnjoj]

This sounds like a great idea, Agniusm. do you have a price and available date for shipping?
otherDoc

 

[999zip999]

Back to charging. If using a bms it will charge to 3.7-3.85v to bleed down. With the charger on and balancing for hours. the cells being more at hvc. this will lower cell life ? If so living a ping on the charger for days or always to balance would lower cell life ?

 

[miro13car]

Doc,
one question since you did not publish any A123 20Ah cells pictures you receved:
do cells have any letters printed in the CENTER on either side?
A 123RC ones have right in thecentre printed "B".

 

[Doctorbass]

Doc,
one question since you did not publish any A123 20Ah cells pictures you receved:
do cells have any letters printed in the CENTER on either side?
A 123RC ones have right in thecentre printed "B".

Please go back to the few first pages of that thread and read! :wink:

You can clarely see i'm showing my cells in this video:

[youtube]ZtQvmURq3nQ[/youtube]


This video too :

[youtube]UPTRoLKlHpg[/youtube]


Here:

and Here:

Do you still think i did not posted any pictures or video?

The cell i got also have a B printed right in teh center of the cell

Some have A2 and A1 also in the middle.

I dont know what it mean.. and i doubt it could be the grade...


Doc



Doc

 

[Doctorbass]

Back to charging. If using a bms it will charge to 3.7-3.85v to bleed down. With the charger on and balancing for hours. the cells being more at hvc. this will lower cell life ? If so living a ping on the charger for days or always to balance would lower cell life ?

Yes this reduce the cell life by a given margin.. i can not say how much.. but it does. Any lithium cells dont like to be sustained at HVC for long time

This is true that the ping BMS that is pushing the cells to up to 3.9V until all cell are equalized is reducing their life. BUt i never did any "destructive" test for testing that.

Doc

 

[miro13car]

Sorry Doc.
I admit I DID NOT watch your videos carefully.
However , do you see any connection between those letters and measured capacity?

 

[agniusm]

Hi, i have got cells from Victpower last year and did the capacity test. It was one cycle thou. Here is a list including lettering on the cells. Interestingly one cell went flimsy (gel feel inside and nasty smell??!!) after one charge/discharge cycle, another one softened up but not as much. I started using my pack as of yesterday, 12S 20AH took me 34km.
Here is the link for spreadsheet to compare:https://docs.google.com/spreadsheet/ccc?key=0Ap6NVZIdTBFOdE1zXzN3ZzhyYkoxb0g2WjJuSmdiX2c#gid=0

 

[Doctorbass]

UPDATE 8 APR 2012


I did a 5C ( 100A) continuous discharge test until 2.0V lvc at 22 degree C ambiant for the first 10 cells i have.

Here is the results:

Cell 1: 18.48Ah temp at the end: 52.7 celsius
Cell 2: 18.26Ah temp at the end: 51.8 celsius
Cell 3: 18.37Ah temp at the end: 52.0 celsius
Cell 4: 18.42Ah temp at the end: 52.3 celsius
Cell 5: 18.45Ah temp at the end: 52.5 celsius
Cell 6: 18.40Ah temp at the end: 52.0 celsius
Cell 7: 18.73Ah temp at the end: 53.2 celsius
Cell 8: 18.70Ah temp at the end: 51.7 celsius
Cell 9: 18.37Ah temp at the end: 51.6 celsius
Cell 10: 18.40Ah temp at the end: 52.1 celsius

Conclusion for the 10 first cells tested at 5C continuous: the capacity variation is 2.55%

 

[miro13car]

agniusm,
can you spare me reading all your threads and tell me how you measured capacity,what equipment?
I did 20A untill 2V cut off tests on CBAIII for my 12 cells from A123RC and results are rather misarable. Only 2cells reached 19Ah on 2Vcut off.
All my cells are marked B in middle.
I tend to conclude that those letters mean grade, your results confirm that.

 

[dnmun]

nonsense, they don't confirm anything. more likely they just indicate which production line they came from. you guys are always cooking up fantasies about how these cells are defective. no wonder jack called this place "endless fear". what does it take to get you to understand that? JD even had a video of the manufacturing operation.

there is nothing wrong with these cells, i think the doc has proved it beyond anyone's wildest distortions.

 

[Doctorbass]

agniusm,
can you spare me reading all your threads and tell me how you measured capacity,what equipment?
I did 20A untill 2V cut off tests on CBAIII for my 12 cells from A123RC and results are rather misarable. Only 2cells reached 19Ah on 2Vcut off.
All my cells are marked B in middle.
I tend to conclude that those letters mean grade, your results confirm that.

miro13car, there is a BiiiiG PROBLEM with the uncompensated CBA:

The the voltage measurement of the CBA is not really accurate since at 20A the resistance loss in the connections make the CBA thinking that the voltage is lower than the real voltage on the cell !!

Usually accurate test equipment will have a kelvin connection ( 4 wire method) so the voltage reading is not made by the same wire than the discharge current circulate and it eliminate the voltage drop across the wire and contact loss.

You can test that. Just make a 20A test and measure the voltage on teh cell tab directly with a good multimeter and also watch the voltage that the CBA is displaying.

What i mean is that your CBA might trip the LVC too soon ! Due to the bad voltage measurement described above, It "think" the cell reach the LVC but i bet that it is still above.. like around 2.5V or so...

The new CBA III program allow you to compensate for that error in a calibration section of the program. If you watch carefully all info i provide in my test video, i explain that compensation and also show that the voltage difference of mine between the cell tab and the program display is only 30mV at 100A ! :wink:

I bet after you will have corrected that and also will have doubelchecked that the current calibration also is ok on your CBA, you will measure a more realistic and higher capacity :wink:

Never forget that the accuracy of your results depend on your instrument... and that your instrument result depend on how you operate your devices :wink:


Doc

 

[agniusm]

agniusm,
can you spare me reading all your threads and tell me how you measured capacity,what equipment?

I bought that iCharger 206b, charged up each cell to 3.65V and then discharged it to 2.00V with balance wires connected. I bet its not accurate, but good enough for me.

nonsense, they don't confirm anything. more likely they just indicate which production line they came from. you guys are always cooking up fantasies about how these cells are defective. no wonder jack called this place "endless fear". what does it take to get you to understand that? JD even had a video of the manufacturing operation.
there is nothing wrong with these cells, i think the doc has proved it beyond anyone's wildest distortions.

Where do you get that bitterness towards people here? There is nothing wrong if cell is b grade, it only means that it did not met requirements. Same as with solar cells, they make them same as i was told and then sort out regarding quality and output which cells will be 265W and which 240W although they were made on the same line possibly on the same hour.
Now, there are bad cells out there and i had them, mine were marked as Korean. For fact "Dnmun" will not agree or trust anyone as he has magic powers to breath in life to dead cells but thats another story

Oh and if i get a cell that shows 18AH, fine with me, remember that for A grade cells you will pay 99USD a piece from mavizen or 65USD if purchase 1000pcs. I dont think 2AH worth 69USD
As long as they are alive, i am happy paying 30USD per 18 ah cell.