What IS correct lithium cut off voltage?

What IS correct lithium cut off voltage?
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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> What IS correct lithium cut off voltage?

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What IS correct lithium cut off voltage? - 7/8/2003 7:43:05 PM

WLB

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Joined: 2/11/2002
From: Waterloo, IA, USA
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I have read you should stop flying and recharge lithium flight packs when under a 1 amp load they reach anywhere from 6 volts to 7.1 volts. What is THE correct voltage for recharge? Also what is the never go below voltage? Thanks.

What IS correct lithium cut off voltage? - 7/8/2003 7:48:53 PM

Red Scholefield

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Joined: 12/8/2001
From: Newberry, FL, USA
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All the testing I have been doing on Lithium-polymer is done with the charge voltage clamp set at 4.2 volts/cell with a 0,5C current limit - charge terminated when current drops to 0.03C. On discharge - up to 10C with voltage cut off at 3.0 volts/cell.

The 3.0 volts cut off gives you a good saftey margin yet if you look at the curve the voltage is dropping rather fast at this point so you don't loose much capacity.

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What IS correct lithium cut off voltage? - 7/9/2003 2:28:28 AM

Posts: 177
Joined: 12/29/2001
From: Salt Lake City, UT, USA
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Red when you get to the large packs (replacement for 20,24 or 30 nicad cells) does the speed controler ie Hacker ESC 77-3P OPTO take care of this cut off. What chargers are available to handle this size of a pack as I understand that if not charged properly that a fire can result. What life could you expect from a pack, I read up to 500 cycles which would be about $1.00 per flight ( $500 is the price on Esprit Models web site) as Gary W put it it is not cheap to go to electrics. But at a $1.00 foe 10 to 20 minutes is not to bad. Thanks.

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What IS correct lithium cut off voltage? - 7/9/2003 4:33:14 AM

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From: Elverta, CA, USA
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I understand the no fly voltage is 6.8-7.0V under a 1.5 amp load depending on who you talk to.

I have read that discharging these cells to and below 2.5V per cell or 5.0V per battery pack may cause permanent damage to the cells. One should never allow these cells to get this low. In the event you inadvertently leave the switch on you might look hard at the battery pack thereafter.

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What IS correct lithium cut off voltage? - 7/9/2003 5:19:42 AM

Red Scholefield

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From: Newberry, FL, USA
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[QUOTE]Originally posted by bpannier
Red when you get to the large packs (replacement for 20,24 or 30 nicad cells) does the speed controler ie Hacker ESC 77-3P OPTO take care of this cut off. What chargers are available to handle this size of a pack as I understand that if not charged properly that a fire can result. What life could you expect from a pack, I read up to 500 cycles which would be about $1.00 per flight ( $500 is the price on Esprit Models web site) as Gary W put it it is not cheap to go to electrics. But at a $1.00 foe 10 to 20 minutes is not to bad. Thanks. [/QUOTE]

Lithium is the new kid on the block. I don't think anyone has a good handle on the capability and limitations particularly in the sizes you are talking about.

6 lithium in series . . . when you consider they are a constant voltage device is scary when you start thinking about keeping them balanced.

I am running just two in series and am using a tap to be able to measure each cell after a few flights to make sure they have not drifted apart. This gives me the capability of charging each individually to bring them back in balance.

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Red S.
AMA 951 Leader Member
Disclaimer: What I have written here are my thoughts and in no manner shape or form reflect the views of RCU

(in reply to WLB)

What IS correct lithium cut off voltage? - 7/9/2003 7:28:42 AM

Posts: 177
Joined: 12/29/2001
From: Salt Lake City, UT, USA
Status: offline

THANKS I think I will wait for a while. and stay with the nicads it was for weight as my 24 cell pack is a little over 3lbs and it was suggested to go to 30 cells which would add more weight. Should not have gone to the TOC and watched Gary and Steve sure was inpressive. Also 5200 feet and 90 plus does not help either.

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