HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 07, 2005, 12:41 PM
Registered User
Joined Apr 2005
1 Posts
Low Current and LiPo Low Voltage Cutoff?

I've searched but not found a great answer...

So, I've been playing with my first 2S 1200ma lipo on a Hyperion E-Meter and a cdrom motor. Haven't put it in a plane yet...

There is a heckuva difference in voltage at say 4C (wide open) discharge as opposed to 1C (1/3 throttle). The voltage doesn't drop as much at low throttle.

With a Lipo, typical LVC is 3.0V/cell, however, I have heard that you should not charge a Lipo that is reading less than 3.3V/cell. I therefore assume that the 3.0V cutoff is dependant on voltage drop due to load, and the resting voltage needs to be somewhat higher.

So, my question is this: If I'm just tooling around the yard at part throttle, is it possible to over-discharge my LiPo?
cserwin is offline Find More Posts by cserwin
Reply With Quote
Sign up now
to remove ads between posts
Old May 07, 2005, 01:16 PM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,812 Posts
Quote:
Originally Posted by cserwin
I've searched but not found a great answer...

So, I've been playing with my first 2S 1200ma lipo on a Hyperion E-Meter and a cdrom motor. Haven't put it in a plane yet...

There is a heckuva difference in voltage at say 4C (wide open) discharge as opposed to 1C (1/3 throttle). The voltage doesn't drop as much at low throttle.

With a Lipo, typical LVC is 3.0V/cell, however, I have heard that you should not charge a Lipo that is reading less than 3.3V/cell. I therefore assume that the 3.0V cutoff is dependant on voltage drop due to load, and the resting voltage needs to be somewhat higher.

So, my question is this: If I'm just tooling around the yard at part throttle, is it possible to over-discharge my LiPo?
ESCs LiPolys and LVC explained here.
To see how volts under load varies visit there.
everydayflyer is offline Find More Posts by everydayflyer
Reply With Quote
Old May 07, 2005, 04:11 PM
Registered User
Terry Rigden's Avatar
UK, Bedworth
Joined Apr 2004
2,636 Posts
Yes but that doesnt answer the original question (and I had been wondering the same thing)

So what is the safe cut off voltage at say
2C 3c 4c etc

Terry
Terry Rigden is online now Find More Posts by Terry Rigden
Reply With Quote
Old May 07, 2005, 05:02 PM
Registered User
IA-Flyer's Avatar
United States
Joined Nov 2003
1,495 Posts
3.7v per cell is very safe at all those discharge rates, the only problem is flight times could be very short!


Try “soft cutoff” at around 3.4v per cell.
Look for an after flight no-load voltage of 3.7v per cell.
Adjust the voltage higher or lower depending on your results.
IA-Flyer is offline Find More Posts by IA-Flyer
Reply With Quote
Old May 07, 2005, 06:04 PM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,812 Posts
Quote:
Originally Posted by terry.rigden
Yes but that doesnt answer the original question (and I had been wondering the same thing)

So what is the safe cut off voltage at say
2C 3c 4c etc

Terry
THe safest LVC to use with LiPolys is one which results in an open cell voltage of atleast 3.5 volts per cell with 3.7 volts per cell being much easier on the cells / batteries. THe voltage under load does not rally mater that much as long as the battery spring / bounches back above these levels as soon as the load is reduced / removed. A high drain / load when removed wiil cause the battery to spring back more than if a light load was removed.
There is no magic numbers other than open cell / resting voltage.
As LiPolys are improved and are able to discharge a greater percentage of their capacity above 3 volts per cell under load it become easier to over dischage them to the point that they will not recover to 3.5-3.7 volts when the laod is removed. Not deep discharging LiPoly cells in general add greatly to their life expendency.
Example: Last summer I used E Tec 1200 Classic LiPolys rated at 6C and flew to a LVC of 7.2 volts or 2.4 volts per cell ,soft cutoff. This did not unduely harm the batteiries and was a common recommended practice at that time.
Apogeee ,Tanic and Thunder Power all now clearly state not to use a LVC of less than 3 volts per cell with any of their current LI Poly batteries.

LiPolys ,ESCs and LVC.

Charles
everydayflyer is offline Find More Posts by everydayflyer
Last edited by everydayflyer; May 07, 2005 at 06:18 PM.
Reply With Quote
Old May 08, 2005, 11:22 AM
Registered User
Terry Rigden's Avatar
UK, Bedworth
Joined Apr 2004
2,636 Posts
Thanks guys that clarifies thing a lot.

regards

Terry
Terry Rigden is online now Find More Posts by Terry Rigden
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Lipo Low Voltage Cutoff andyg Batteries and Chargers 1 May 19, 2005 07:31 PM
What happens when a Lipo hits the esc low voltage cutoff? Rackey Batteries and Chargers 7 Jan 05, 2005 08:27 AM
Lipo flyers who don’t use low voltage cutoff rush Batteries and Chargers 42 Dec 29, 2004 05:14 PM
Lipo's and Voltage Cutoff aplphabandaid Batteries and Chargers 3 Jan 13, 2004 11:28 AM
Corona-3S lipo and CC35 voltage cutoff? ICRSHLTS Electric Heli Talk 11 Nov 03, 2003 09:59 AM