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Old Jan 27, 2013, 09:52 AM
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Optimum charge rate

My Hyperion batteries state not to charge faster than 6C. Fair enough.

However, is there a charge rate that is better for the battery's health than the fastest allowed? Can you charge a LiPo too slowly?
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Old Jan 27, 2013, 10:26 AM
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Originally Posted by kallend View Post
My Hyperion batteries state not to charge faster than 6C. Fair enough.

However, is there a charge rate that is better for the battery's health than the fastest allowed? Can you charge a LiPo too slowly?
This has been covered over and over and over again. In short No and No. Some people still believe that charging faster then 1C shortens the life but in practice no one has found that to be true on modern lipos. Majority of people charge at 3C-5C I would say.
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Old Jan 27, 2013, 08:17 PM
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Originally Posted by grimbeaver View Post
This has been covered over and over and over again. In short No and No. Some people still believe that charging faster then 1C shortens the life but in practice no one has found that to be true on modern lipos. Majority of people charge at 3C-5C I would say.
Couldn't agree more. Newer designs have better chemistry and construction which makes for lower internal resistance. This improves discharge and charge capacity.
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Old Jan 29, 2013, 07:40 PM
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Originally Posted by grimbeaver View Post
This has been covered over and over and over again. In short No and No. Some people still believe that charging faster then 1C shortens the life but in practice no one has found that to be true on modern lipos. Majority of people charge at 3C-5C I would say.
Based on the number of questions on this exact topic over the past few days, maybe the "over and over again" needs to be somewhere easy to find instead of buried among thousands of posts in dozens of different threads.

Just a friendly suggestion.
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Old Feb 02, 2013, 10:59 AM
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Does charging at 5c mean 5amps, or is there a conversion to figure what amp you should charge at
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Old Feb 02, 2013, 11:03 AM
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5C means 5 x capacity in Ah.

e.g. - a 2200mAh pack charged at 5C would be: 5 x 2.2 = 11A.

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Old Feb 02, 2013, 11:05 AM
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Originally Posted by xfatdannx View Post
Does charging at 5c mean 5amps, or is there a conversion to figure what amp you should charge at

5C = 5x the battery capacity.
For instance a 4000 mah battery would be a charge rate of 20 amps at 5C.
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Old Feb 02, 2013, 11:09 AM
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Originally Posted by xfatdannx View Post
Does charging at 5c mean 5amps,
Not really.

"C" X pack capacity (ah or mah/1000) = max charge rate

5C, 2,200 mah pack = 11 amp max charge rate. 5 ("C") X 2.2 (2,200/1000) = 11

"C" in this case meaning the manufacturers' recomended max charge rate, NOT the (usually more visible) advertised discharge rating.
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Old Feb 02, 2013, 02:16 PM
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perfect, thanks guys. My batteries can not charge at their max rate anyway bc my charger can only do 6a. Very good to know, i appreciate it.
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Old Feb 02, 2013, 07:39 PM
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What is the reason for not being able to charge at as high a C rate as the battery can be discharged?

i.e., why can a 25C battery not be charged at a 25 C rate?

Just wondering.
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Old Feb 02, 2013, 07:48 PM
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Most chargers cannot do such except on very small cells. Understand that most 25C rated packs cannot even tolerate a 25C discharge without damage. That said, I have charged a 2200 mAh pack at 30 amps before and it simply entered CV stage almost immediately. Still using said pack.
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Old Feb 02, 2013, 09:14 PM
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Most chargers cannot do such except on very small cells. Understand that most 25C rated packs cannot even tolerate a 25C discharge without damage. That said, I have charged a 2200 mAh pack at 30 amps before and it simply entered CV stage almost immediately. Still using said pack.
Mark
So, is there really any reason to not charge at the max C rate posted for the battery?

Is there a significant difference in reversing the process of discharge vs recharge?
Why has it traditionally always been the recommendation to do a slow charge?

Sorry - there are always more questions then answers. If there weren't then no one would progress.
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Old Feb 02, 2013, 10:03 PM
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Originally Posted by midnite View Post
So, is there really any reason to not charge at the max C rate posted for the battery?

Is there a significant difference in reversing the process of discharge vs recharge?
Why has it traditionally always been the recommendation to do a slow charge?

Sorry - there are always more questions then answers. If there weren't then no one would progress.
From the materials science point of view there is DEFINITELY a difference between charge and discharge in the microstructures developed in the electrode materials.

Just like there's a difference between hailstones and snowflakes although they are chemically the same.
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Old Feb 02, 2013, 10:27 PM
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From the materials science point of view there is DEFINITELY a difference between charge and discharge in the microstructures developed in the electrode materials.

Just like there's a difference between hailstones and snowflakes although they are chemically the same.
If you care to - please expand - in very simple terms, one is just the reverse of the other. Why should the process in one direction be done faster more safely than the other? There's an obvious limit but if there's a difference in the microstructures developed at a reasonable speed why can it not be equal in either direction?

From the following site - http://www.mpoweruk.com/life.htm
- is this quote - "Trying to force too much current through the battery during the charging process results in surplus ions being deposited on the anode in the form of Lithium metal. Known as Lithium plating, this results in an irreversible capacity loss. At the same time, maintaining the higher voltages needed for fast charging can lead to breakdown of the electrolyte which also results in capacity loss."

There is a correlation to charging faster than 1 C and shortened battery life. But what is the correlation to speed of discharge and battery life? Why cannot they be the same? I understand there must be a complicated response to do this question justice - but if anyone has a quick and dirty answer that provides some specifics that will satisfy a curious mind then ...

After all - you can fill a glass full of water as fast as you can empty it - no change in chemical structure though. So what are the differences in battery charge and discharge?
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Old Feb 03, 2013, 03:26 PM
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Originally Posted by midnite View Post
If you care to - please expand - in very simple terms, one is just the reverse of the other. Why should the process in one direction be done faster more safely than the other? There's an obvious limit but if there's a difference in the microstructures developed at a reasonable speed why can it not be equal in either direction?
Same reason as dissolving sugar in water to make sugar solution can be done faster than crystallizing solid sugar from sugar solution. Same reason that melting quartz can be done in a few seconds, but crystallizing quartz from the molten state takes months.

And in terms of speed, just think of the difference between slowly cooled steel and steel that has been quenched in cold water.
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