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Old Jan 04, 2005, 11:37 AM
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Rackey's Avatar
Savannah, Ga
Joined Apr 2002
130 Posts
What happens when a Lipo hits the esc low voltage cutoff?

I am new to lipos and recently aquired some polyquest 3s 2100 batteries. I have been flying them but have never hit the programmed low voltage cutoff in my CC-25 and have been very careful not to. However, I have triggered the low voltage cutoff when using Nmhi and Nicads and what I find is that if I immediately kill the throttle and wait a few seconds the battery will recover somewhat which can give me some limited throttle for landing. Do lipos react with a limited recovery in the same way? Or is it dead stick every time you hit the low voltage cut off with a lipo.

Thank you for reading.
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Old Jan 04, 2005, 11:44 AM
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Willoughby, Ohio
Joined Apr 2004
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You'll get the same effect. When the esc cuts out, the pack voltage will rebound. However, unlike nimh and nicd, if you keep doing it, you may damage the pack. I would recommend powering back up ONLY to bring it in for a landing. There's no reason to push it, you'll just damage the pack and possibly have a "hot" situation on your hands.

matt
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Old Jan 04, 2005, 02:44 PM
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fly4fun's Avatar
Gilbert AZ
Joined Jun 2001
9,323 Posts
Ditto of What Matt Said.

Also I recommend Soft Cut off instead of Hard Cut off. With Soft the RPM Starts to surge and sage but you have enough power to bring her in and land. With Hard Cut Off your power is lost to the motor and you might be force to do a dead stick landing if your flying to low and not have enough time to regain power and land.

David
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Old Jan 04, 2005, 04:37 PM
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Savannah, Ga
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Thank you for your advice and swift replies.
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Old Jan 04, 2005, 06:23 PM
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Chicago Midway, Illinois, United States
Joined Jul 2003
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Also suggest you read the Castle description of the controller settings PDF

http://www.castlecreations.com/docum...20Settings.pdf
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Old Jan 04, 2005, 07:19 PM
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Savannah, Ga
Joined Apr 2002
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Thanks flatfour the reference, the explanation is very comprehensive. However, I do not have a phx link. My origional question was really a Lipo battery question but the answers have caused me to think about hard vs soft cut-off. I have had my CC-25 programed for a 9 volt hard cutoff and have used hard cutoff with my Nicads and Nimh packs as well. The hard cutoff seems to me to announce the final approach in a very dramatic way. My initial thinking was that I might miss the signals of a soft cut off. I don"t (not yet) do any 3d and keep things high. I will experiment and feel it out. Thanks again.
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Old Jan 05, 2005, 07:51 AM
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fly4fun's Avatar
Gilbert AZ
Joined Jun 2001
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Rackey If you do not do any low level aerobatics or 3D Flying then hard Cut Off is fine. Also if all you do is fly floater type airplanes then Hard Cut is perfect. Hard Cut Off with a Heli Yikes!

David
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Old Jan 05, 2005, 08:27 AM
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Haralson County GA. USA
Joined Oct 2004
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Quote:
Originally Posted by fly4fun
Rackey If you do not do any low level aerobatics or 3D Flying then hard Cut Off is fine. Also if all you do is fly floater type airplanes then Hard Cut is perfect. Hard Cut Off with a Heli Yikes!

David
I have not flown Hellies for a number of years now however my son and I do fly 3D Fomies a great deal. We only use soft cutoff and it works extremely well.
The only point that I feel is worth noting is that with soft cutoff it is not a good idea to cruise / float around at low throttle when reaching what most likely is the end of your batteries capacity. If I am flying a setup which provides normal 15 minute flights then once I reach the 10 minute point I make a point of punching the throttle to WOT every so often to see if motor is pulsed ( soft cutoff).

Charles
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