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Old Oct 05, 2008, 06:52 PM
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Melbourne, Australia
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Quote:
...I once connected a fully charged and a fully discharged pack (100% charge difference), and the current was about 2C initially
That's "2C" not "2A" right ? So if they were 1000mA packs it would have been about 2A or 3300mA packs about 7A ?
Quote:
While the resting voltages might have a considerable difference, as soon as a pack is charged, its voltage rises rapidly, and the voltage of a discharged pack decreases rapidly, this making the actual voltage difference of 2 connected packs fairly small.
Yes, this is the key. About the middle 80% of the discharge curve is very flat so the voltage differences amongst several partially discharged packs are likely to be small. This is also combined with the fact that you are charging via the thin balance leads which will act as resistors reducing inrush current.
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Old Oct 06, 2008, 05:05 AM
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Yeah, I tested it with 2 2s 850mAh packs, and the current was around 1.7A.
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Old Oct 07, 2008, 02:24 AM
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I assume that was with lipo.

Since A123 have more voltage drop under load,
I would expect the current should be even lower.
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Old Oct 07, 2008, 08:07 AM
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I can test it tonight...
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Old Oct 07, 2008, 05:52 PM
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Excellent thread Julian! Thanks for the well thought out and detailed explanation of parallel charging LiXX. This is sure to become a helpful and often cited reference.

- David
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Old Oct 07, 2008, 06:35 PM
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Quite so! Well done Julian. I have added a link to this thread in the "How to" section of this popular reference page: http://www.helifreak.com/showpost.ph...71&postcount=1
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Old Oct 13, 2008, 03:16 PM
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Hi!

I just connected a fully charged, and a fully discharged 4s 1100 A123 pack.
The initial current was 10A (not more than my usual charge current), and it rapidly decreased. After a minute, I had less than 2A.
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Old Oct 13, 2008, 04:09 PM
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Quote:
Originally Posted by Julez
Hi!

I just connected a fully charged, and a fully discharged 4s 1100 A123 pack.
The initial current was 10A (not more than my usual charge current), and it rapidly decreased. After a minute, I had less than 2A.
Your usual charge current is 9C ?!?!

Dan
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Old Oct 14, 2008, 03:01 AM
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Quote:
Originally Posted by Julez
Hi!

I just connected a fully charged, and a fully discharged 4s 1100 A123 pack.
The initial current was 10A (not more than my usual charge current), and it rapidly decreased. After a minute, I had less than 2A.
Thanks :-)
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Old Oct 14, 2008, 07:44 AM
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Quote:
Originally Posted by Dan Baldwin
Your usual charge current is 9C ?!?!

Dan
Yes?
A123s don't mind
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Old Oct 26, 2008, 02:11 AM
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Julez,

I have begun following your thread with Junsi over at the iCharger forum, and was very impressed with your knowledge and devotion in assisting with the development of the 1010b and 106B+ chargers. I very much appreciate that you took the time to help others like myself begin to comprehend what it is we need and why, thank you!

In reviewing your parallel charging method as outlined in this thread, I was hoping you or another knowledgeable member could point me in the right direction.

I have (4) brand new 3S 20C 2200 Zippy's that have never been charged.

I am looking to purchase a charger that will charge and balance all four packs simultaneously, and yet use them separately or individually.

I noticed you referenced this pic as being another good example of parallel configuration or connection:
http://www.rcgroups.com/forums/showp...postcount=1895

This is exactly what I am looking to do.

Can you tell me what charger I should be looking for? Is there a single charger that is capable of what I am seeking? Is there any danger or folly in what I am asking to be able to do?

Thanks again Julez, for your knowledge and patience.
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Old Oct 26, 2008, 03:15 AM
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To charge 4 x 3s 2200 in parallel as 3s4p 8800 at 1C you need a charger capable of at least 100W output at 8.8A. The iC106B+ (6s, 250W/10A) would be ideal. You would need top make up an appropriate balance-charge adapter to connect the balance leads of all the packs in parallel and a matching main lead adaptor, as shown in the first post of this thread.
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Old Oct 26, 2008, 03:34 AM
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Quote:
Originally Posted by kgfly
To charge 4 x 3s 2200 in parallel as 3s4p 8800 at 1C you need a charger capable of at least 100W output at 8.8A. The iC106B+ (6s, 250W/10A) would be ideal. You would need top make up an appropriate balance-charge adapter to connect the balance leads of all the packs in parallel and a matching main lead adaptor, as shown in the first post of this thread.
Thank you kgfly, it's hard to understand why not many people have heard about this already, if it is as simple as this. I am most surprised that manufacturers aren't selling parallel cables as an option or included equipment, why aren't they touting this as a selling feature?

Is there anything else I should be cautious or aware of when charging in parallel?

Will the life expectancy of the packs be diminished in any way?
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Old Oct 26, 2008, 04:06 AM
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It is not an off-the-shelf solution and many are reluctant to take a risk that they might get it wrong and cause a disaster. Given the potential bad outcomes with LiPo batteries being cautious is wise. I have gone down the path of having more chargers rather than charging more packs in parallel on the one charger, in part due to my interest in the chargers themselves and in part because until recently I too was concerned that the initial inrush current might be damaging. Having learned more and having moved part of my fleet to A123, I am no longer concerned about that aspect.

If you are concerned, send a PM to Rampman on this forum, he makes a parallel charging adapter board which guarantees to limit the cell-to-cell current to 1A, which is bound to be very safe IMO.
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Old Oct 26, 2008, 04:40 AM
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Joined Aug 2007
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Hi

The Cellpro 4S charges through the balance leads ., I guess you know that

If I wanted to parallel, charge and balance , 4 off 3S 900Mah batteries


can I just connect ( charge ) to one balance lead, and connect the others together, in parallel
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