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Is this normal?

Old 03-20-2011, 01:51 AM
  #1  
Southpaw
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Default Is this normal?

I'm relatively new to the Lipo field so I have to ask...

I have a couple packs that I fly with that have less than 10 flights each.

They both seem to have one cell that will drop off rapidly compared to the other two.

One will drop the cell to 0 volts while the others have 3.6 left. I understand this is bad.

The other pack will drop to 3 volts leaving the other two at 3.6. I balance charge and check voltages pretty regularly.

Any thoughts or suggestions?

Other than take them out back and make another destructive YouTube video.

They are 20c packs of different brands and are not really being used near their limits.
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Old 03-20-2011, 02:35 AM
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flydiver
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If you are flying to LVC and you have an ESC with a low setting (many brand name ESC have poor LVC settings - yes, they do). You are over discharging the lipos. Near the end of capacity the voltage drops off VERY FAST! The cells with remaining voltage could be very near exhausted while the bad one obviously is. The bad one has taken some extra hits now and is even worse off. It won't improve.

That said, 3.6/3.6/0 is NOT healthy, ever. 3.6/3.6/3.0 isn't so hot either.
Try flying a couple minutes less. Do not fly to LVC. Be prepared to discard those packs. In the meantime watch them carefully and consider them suspect.

FWIW, just because a pack 'claims' to be 20C doesn't mean it is 20C. There's hardly a pack out there that can actually measure up to marketing BS. It's a safe bet you can de-rate almost anything by 20%.
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Old 03-20-2011, 04:31 AM
  #3  
kyleservicetech
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Originally Posted by Southpaw View Post
I'm relatively new to the Lipo field so I have to ask...

I have a couple packs that I fly with that have less than 10 flights each.

They both seem to have one cell that will drop off rapidly compared to the other two.

One will drop the cell to 0 volts while the others have 3.6 left. I understand this is bad.

The other pack will drop to 3 volts leaving the other two at 3.6. I balance charge and check voltages pretty regularly.

Any thoughts or suggestions?

Other than take them out back and make another destructive YouTube video.

They are 20c packs of different brands and are not really being used near their limits.
Read my thread below on electrifying 70 sized glow models to electric. Chapter XIV covers "How to Kill a Lipo".

http://www.wattflyer.com/forums/showthread.php?t=45222

Hopefully this will help explain what can happen.
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Old 03-20-2011, 04:01 PM
  #4  
Southpaw
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That's some good info, definately worth saving. I noticed there are some more expensive ESC's out there that hook up to the charge port to monitor individual cells for the LVC.

Now I understand why.
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