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Old Dec 01, 2012, 01:10 PM
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Routinely discharging packs to 3.3V(+/-) is not recommended. Usually it is done for two reasons: 1) Determining capacity and 2) Safe-ing a pack to work on.
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Old Dec 01, 2012, 02:09 PM
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Quote:
Originally Posted by seefest View Post
Quick question about cycling discharge voltage. When cycling a lipo pack, should they be discharged to 3.3v or 3.0v?
I've had chargers that discharged to 3.0v but my PLA 8 is configurable. Its default is 3.3v, but can be set lower. Thanks in advance.
If you are taking about discharging to storage voltage, 3.85V / cell is where you want to be.
Never discharge below 3.70V / cell.
It will shorten the life of your packs.
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Old Dec 01, 2012, 08:22 PM
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Beg to differ li-ion or li-poly - basically the same thing can run down to 3.0v per cell. for rc application maybe better to stay at about 3.3v
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Old Dec 01, 2012, 08:33 PM
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Anyone is welcome to use lipos down to a resting voltage of 3 volts , but other than radio batts they are "worthless" at that level. Even radio batts can be "worthless" if they are taxxed heavy.

RevoJohn, would you say there's no damage to lipo at 3 volts resting? I'm considering long term storage at that voltage level.
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Old Dec 01, 2012, 08:35 PM
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Originally Posted by REVOJohn View Post
Beg to differ li-ion or li-poly - basically the same thing can run down to 3.0v per cell. for rc application maybe better to stay at about 3.3v
You and the WoodCrafter are both correct but you are talking about two different voltage circumstances.
The WoodCrafter is saying 3.7V standing voltage after the flight or non-loaded.
You I assume are talking about an under load voltage of 3.0/3.3V during the flight.
Both are right.
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Old Dec 01, 2012, 09:20 PM
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It's recommended that LiPo batteries NOT be cycled, but new ones should be run through about a half dozen 'run' cycles before they can be expected to operate at full capacity.
Also, a charged LiPo pack, of approx 3.98vDC per cell should never be 'peak' charged.

The info contained in the recommended links in my most recent post covered the subject of proper storage conditioning of LiPo battery packs.

http://www.rcgroups.com/forums/showp...&postcount=178


I've noticed that the voltage of new LiPo packs is normally 3.75-3.81/cell.
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Old Dec 02, 2012, 04:57 AM
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Originally Posted by hoppy View Post
You and the WoodCrafter are both correct but you are talking about two different voltage circumstances.
The WoodCrafter is saying 3.7V standing voltage after the flight or non-loaded.
You I assume are talking about an under load voltage of 3.0/3.3V during the flight.
Both are right.
agree. 2 different cicumstances and operation modes

yes lipo can run down to 3.0 but not 3.0 after you come back from a flight because you would have gone well below that during your flight.............
a pack sitting at 3.0 no load......no problem.
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Old Dec 02, 2012, 07:01 AM
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Originally Posted by REVOJohn View Post
agree. 2 different cicumstances and operation modes

yes lipo can run down to 3.0 but not 3.0 after you come back from a flight because you would have gone well below that during your flight.............
a pack sitting at 3.0 no load......no problem.
A pack sitting at 3.0V no load is no problem? At what C-rate would you have to discharge the pack at to have it at a no load voltage of 3.0V and not go below 3V under load?

My guess would be 0.05C. What use would that be to us? That's why a no load voltage of 3.7V after flying is the goal. That's what a flyer will usually see operating at reasonable C-rates and leaving 20% in the tank.

3V no load is not a good number to live by IMO.
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Old Dec 02, 2012, 08:39 AM
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Originally Posted by hoppy View Post
A pack sitting at 3.0V no load is no problem? At what C-rate would you have to discharge the pack at to have it at a no load voltage of 3.0V and not go below 3V under load?

none. you can;t. i said sitting at 3.0v no load. means you can;t go down any further.


My guess would be 0.05C. What use would that be to us? That's why a no load voltage of 3.7V after flying is the goal. That's what a flyer will usually see operating at reasonable C-rates and leaving 20% in the tank.

3V no load is not a good number to live by IMO.
\

.....for flying yes you are right. i'm talking about no load and standard operation range of lithium. 3.0 - 4.2; you are talking about the useful operation of lithium under flight load which yes of course is heavy we all know.............but you did not define that in your original comment thus i make the clarifications here
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Old Dec 02, 2012, 08:43 AM
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I agree, the discharge rate would have to be very tiny. As we all know, the difference between open and loaded voltage gets wider as the current goes up. Speaking about a loaded voltage is as one poster coined, "a moving target" and can range from meaningless to spot on accurate. The resting voltage is key , not the loaded voltage. I'm not saying anything new here.

John, however is saying that 3.0 resting is ok. I guess I have heard a lot of people state that same figure now that I think about it. I'm going to check that out soon enough. I've always used 3.5 as my bare minimum.
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Old Dec 02, 2012, 10:04 AM
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Originally Posted by REVOJohn View Post
\

.....for flying yes you are right. i'm talking about no load and standard operation range of lithium. 3.0 - 4.2; you are talking about the useful operation of lithium under flight load which yes of course is heavy we all know.............but you did not define that in your original comment thus i make the clarifications here
My comments/definitions were based on the use of LIPOs by RC flyers as this is a RC forum.
The problem with stating that 3V no-load is OK is that without defining the C-rate necessary to obtain that 3V no-load could lead many down the wrong path. Unfortunately, few planes could stay in the air trying to run them down to 3V no-load as the batteries would be completely empty.
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Old Dec 02, 2012, 11:15 AM
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My comments/definitions were based on the use of LIPOs by RC flyers as this is a RC forum.
Exactly, We are not in a laboratory here.
This is an RC forum, so lets stick to how these batteries are used in our hobby.
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Old Dec 02, 2012, 05:19 PM
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well i wouldn;t say labortory but general consumer electronics vs rc hobby stuff definitey. funny that most people you see on the forums are petrified of lipo but they are probably carrying one in their pocket everday of the week. just that lipo was never meant to be for rc........but it works.....within careful limitiations.
as per of revolectrix, we'll be making lipo educational vidoes within the next few weeks
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Old Dec 02, 2012, 06:08 PM
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Nominal voltage for a LiPo battery cell is 3.7vDC, and a fully charged LiPo cell voltage is 4.2vDC.
A LiPo battery cell should never be discharged below 3.0vDC or charged beyond 4.2vDC, because to do so will most undoubtedly cause irreparable damage!

The purpose of the LVC circuitry of an ESC is to protect the battery pack from the consequential damage of inadvertent discharge beyond 3.2vDC per cell (under load). The cell then 'bounces back' to approx 3.4vDC per cell once the load is removed.


I've been tracking the maintenance and performance of all of the batteries that I use in my RC planes, and support equipment for five (5) seasons now, and one of the things I've noticed is that LiPo cells recover an additional 0.04vDC per cell within 24 hrs after use.

http://www.rcgroups.com/forums/showp...9&postcount=24

Most of my batteries are 3S 1P 2200 mAh 25-30C LiPo. I have an average of 88 cycles(documented) among four (4) of my oldest LiPo packs. One of them, alone, has just over 170 cycles on it since July, 2009.
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Old Dec 03, 2012, 10:41 AM
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Originally Posted by hoppy View Post
Routinely discharging packs to 3.3V(+/-) is not recommended. Usually it is done for two reasons: 1) Determining capacity and 2) Safe-ing a pack to work on.
Thats what I meant. Sorry if I wasn't clear. For determining capacity reasons.
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