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  #11  
Old 02-02-2012, 09:59 AM
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Default Re: A123 20Ah pack configuration question

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Originally Posted by rwaudio View Post
I'm charging to 3.65 at 38A that terminates at 0.9A and discharging to 2.25v with a 38A constant current.
The PL6 will do everything automatically. You can actually hook up to 16 PL6's together and control them all from one PC interface.
I think I'll order some additional ones like you say. How do they connect together and how does the interface on the computer change when you have several of them all hooked together? I'm thinking of getting 3 more to have 4 total.

Could you use a higher cut off voltage like 2.85V to save time, then correlate an average of the existing curves to predict the capacity instead of running it all the way to 2.25V? You may not save that much time, but times 500 it could add up.
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  #12  
Old 02-02-2012, 10:43 AM
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Default Re: A123 20Ah pack configuration question

I didn't read all the details so excuse me if this has been covered but I just want to mention that you don't need multiple PL units to do more batteries. I have a PL 8 and I do 6 cells connected in series, at one time. With balance and charge leads connected, you can get individual IR readings and individual capacities. You can balance charge or not depending on settings. u can finish at top or bottom or anywhere u like . . on the voltage scale.
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Old 02-02-2012, 11:30 AM
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Default Re: A123 20Ah pack configuration question

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Originally Posted by DIYguy View Post
I didn't read all the details so excuse me if this has been covered but I just want to mention that you don't need multiple PL units to do more batteries. I have a PL 8 and I do 6 cells connected in series, at one time. With balance and charge leads connected, you can get individual IR readings and individual capacities. You can balance charge or not depending on settings. u can finish at top or bottom or anywhere u like . . on the voltage scale.
An important point for me would be to know the time it takes. I thought the PL6 could only deliver 40A max. If this is distributed over multiple batteries like 6 since that why it has its name that the amperage would go down and the whole process would take longer.

I haven't used my PL6 yet so I'm not positive about this. My goal here is to measure the capacity while bottom balancing the pack. The idea of 6 batteries at once might be useful. Meaning instead of changing the batteries out every 45 minutes, I could change 6 batteries out every 270min (6*45min). This may be work investigating for working with a large number. I still think that I'll need multiple PL6s in order to complete 500 in a reasonable amount of time.
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Old 02-02-2012, 11:41 AM
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Default Re: A123 20Ah pack configuration question

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Originally Posted by kakheath View Post
An important point for me would be to know the time it takes. I thought the PL6 could only deliver 40A max. If this is distributed over multiple batteries like 6 since that why it has its name that the amperage would go down and the whole process would take longer.

I haven't used my PL6 yet so I'm not positive about this. My goal here is to measure the capacity while bottom balancing the pack. The idea of 6 batteries at once might be useful. Meaning instead of changing the batteries out every 45 minutes, I could change 6 batteries out every 270min (6*45min). This may be work investigating for working with a large number. I still think that I'll need multiple PL6s in order to complete 500 in a reasonable amount of time.
yes, your maximum current in and out is still the same. It's the repetitive set up time that may be reduced. It may depend on your connection method but for me, it was a huge improvement. I did 135 cells and let them cycle twice before ending at a specific voltage.

One other thing I found very helpful was to pre-sort according to voltage. If you are doing in series set up. If they are fairly close in voltage, the whole process is shortened dramatically. This is because they must balance before the higher current charge/discharge cycle. I had cells that were in batches kind of and had several different voltage levels. When I grouped them accordingly the process was much quicker. I just went over them with a DVM and put piece of tape on each with the voltage. Then I would grab 6 that were close. At the end I had a handful that were all over the map and I would use a few resistors to bring them in line because I found it was worth the time.

I numbered each and noted IR and capacity in a log. I also saved the files on PC.
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Old 02-02-2012, 11:57 AM
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Default Re: A123 20Ah pack configuration question

thinking about it now, I may have led u a stray. I'm not sure if I got individual capacities or not. I was more interested in individual IR. . . That may be a problem for you if you are grouping according to capacity. Since mine is a high output application, I was grouping according to IR. I can go back and check or maybe RWAudio knows off top of his head since I think he was interested in grouping by capacity.
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Old 02-02-2012, 12:02 PM
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Default Re: A123 20Ah pack configuration question

Quote:
Originally Posted by DIYguy View Post
I didn't read all the details so excuse me if this has been covered but I just want to mention that you don't need multiple PL units to do more batteries. I have a PL 8 and I do 6 cells connected in series, at one time. With balance and charge leads connected, you can get individual IR readings and individual capacities. You can balance charge or not depending on settings. u can finish at top or bottom or anywhere u like . . on the voltage scale.
I did try that as well, and didn't get consistent results. During discharge it will stop the lowest cell and only discharge at 1A to the cut off point which is not the same as the 38A setting I was using. Perhaps I didn't have it configured properly to do it this way but that was just my experience.

I would get a true capacity on the first cell to discharge but once the first cell hit the low cut off it messed up the results for the remaining cells. During charging it does work, but if the cells are very far off the whole balancing thing doesn't work very well with cells of this capacity. Shunting a maximum of 1A doesn't do much on a 38A charge if the cells aren't at the same SOC.

I gave up on that and went to a single cell, if you have any tips on how to do that better I would be happy to hear them. For me getting a capacity number under the same conditions every single time is more important than shaving off a bit of time.
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Old 02-02-2012, 02:31 PM
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Default Re: A123 20Ah pack configuration question

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Originally Posted by rwaudio View Post
You can actually hook up to 16 PL6's together and control them all from one PC interface.
Is there a special cable that is used to connect multiple PL6s together? I have the USB interface for my first one. I'd like to order these cables with the extra units.
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Old 02-02-2012, 03:01 PM
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Default Re: A123 20Ah pack configuration question

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Originally Posted by kakheath View Post
Is there a special cable that is used to connect multiple PL6s together? I have the USB interface for my first one. I'd like to order these cables with the extra units.
servo extension and y cables.
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  #19  
Old 02-07-2012, 05:50 AM
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Default Re: A123 20Ah pack configuration question

Quote:
Originally Posted by rwaudio View Post
I did try that as well, and didn't get consistent results. During discharge it will stop the lowest cell and only discharge at 1A to the cut off point which is not the same as the 38A setting I was using. Perhaps I didn't have it configured properly to do it this way but that was just my experience.

I would get a true capacity on the first cell to discharge but once the first cell hit the low cut off it messed up the results for the remaining cells. During charging it does work, but if the cells are very far off the whole balancing thing doesn't work very well with cells of this capacity. Shunting a maximum of 1A doesn't do much on a 38A charge if the cells aren't at the same SOC.

I gave up on that and went to a single cell, if you have any tips on how to do that better I would be happy to hear them. For me getting a capacity number under the same conditions every single time is more important than shaving off a bit of time.
Well, my batteries arrived and they look great. They all have Made in USA on them and have brand new full size tabs. I'm not sure if I'm using the correct settings, but I managed to charge, discharge and charge again a single cell. I'm using a power supply instead of a 12V battery, so I appear to be limited to 10A up and down. This is terribly slow at about 2 hours each. [IMG]file:///C:/TEMP/moz-screenshot.png[/IMG][IMG]file:///C:/TEMP/moz-screenshot-1.png[/IMG]

rwaudio, when you said you were using a block of A123s in 4s3p for a 12V power supply, how did you get started? Did you balance them individually first or just hook them up and charge them as a pack before balancing? I've measured the initial as-received battery votage of each one and they all appear to be at 3.27-3.28V consistently. Charging the first one up took about 10Ah, so mine appear to be half charged as well. The first cell capacity was 18233mAh. This was from 3.65 to 2.5V. I'm not sure if I'm doing this correctly. so if you have any tips on how to do this more efficiently, I would appreciate it greatly.
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  #20  
Old 02-12-2012, 01:34 PM
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Default Re: A123 20Ah pack configuration question

Quote:
Originally Posted by rwaudio View Post
I did try that as well, and didn't get consistent results. During discharge it will stop the lowest cell and only discharge at 1A to the cut off point which is not the same as the 38A setting I was using. Perhaps I didn't have it configured properly to do it this way but that was just my experience.

I would get a true capacity on the first cell to discharge but once the first cell hit the low cut off it messed up the results for the remaining cells. During charging it does work, but if the cells are very far off the whole balancing thing doesn't work very well with cells of this capacity. Shunting a maximum of 1A doesn't do much on a 38A charge if the cells aren't at the same SOC.

I gave up on that and went to a single cell, if you have any tips on how to do that better I would be happy to hear them. For me getting a capacity number under the same conditions every single time is more important than shaving off a bit of time.
rwaudio, I assembled a 4s3p set of my batteries as a power supply and still seem limited to 10A charge and discharge. Can you tell me why I can't change the setting to 40A? Can you send me your pl6 file so I can check it out? I've been talking to a guy from Quantum Hobby, where I bought my PL6, and he seems convinced that I can do 6 at a time and get the individual capacities if I use his "special" connecter set. We'll see. So far I've tested about a half a dozen down to 2.5V and they ranged from 18.2 to 18.9Ah. I'm not sure how much extra will squeeze out if I go down to 2.25V or even 2.0V.
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