Is 80% discharge safe for Li-Po batteries??

Is 80% discharge safe for Li-Po batteries??
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Is 80% discharge safe for Li-Po batteries?? - 10/3/2006 12:09:12 AM

xalm04

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Joined: 9/13/2004
From: Quito, ECUADOR
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Hi, recently I bought a TP 4200 set of batteries which has 34 flights so long. I have been very careful about their capacity usage and never discharged more than 3200 mAh (around 75%). Is this a good practice?. If I discharge them up to 80% is safe for longevity? Can I make few discharges over 80% (for capacity test purpose) or it affects its performance in the future? BTW when I charge batteries in the field (at about 1.25 C) it takes around 10% more capacity than those charges I made in my home after the battery has rested for a few hours, is this normal? Thanks.

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Xavier Almeida

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RE: Is 80% discharge safe for Li-Po batteries?? - 10/3/2006 3:04:08 PM

exeter_acres

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Joined: 9/22/2004
From: Johns Creek, GA, USA
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depends....the voltage is more important than the mAh...IMHO...
if you are discharging 3400 mAh, but the voltage is dropping below 3v per cell...then it is a problem...
if you are discharging 4200mAh, but the voltage is staying over 3v per cell....then you are fine.....

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RE: Is 80% discharge safe for Li-Po batteries?? - 10/3/2006 3:13:02 PM

xalm04

Posts: 77
Joined: 9/13/2004
From: Quito, ECUADOR
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Thanks very much for your information. So if my batteries are having more than 3V per cell it's OK, but I have 2 questions, first, this voltage (over 3 V) must be measured under charge or with the battery resting? And the second is what is IMHO? I'm not familiar with some abreviations in English. Do you recommend full discharge from time to time to test battery capacity?

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Xavier Almeida

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RE: Is 80% discharge safe for Li-Po batteries?? - 10/3/2006 3:17:59 PM

exeter_acres

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From: Johns Creek, GA, USA
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IMHO = in my humble opinion

and yes...the test should be done under load.. if you have a digital charger, you can just use that...
and I do not discharge my lipo's as it is hard on the batteries... they just don't need it....

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RE: Is 80% discharge safe for Li-Po batteries?? - 10/3/2006 3:19:19 PM

can773

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From: Calgary, AB, CANADA
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quote:

ORIGINAL: xalm04

Thanks very much for your information. So if my batteries are having more than 3V per cell it's OK, but I have 2 questions, first, this voltage (over 3 V) must be measured under charge or with the battery resting? And the second is what is IMHO? I'm not familiar with some abreviations in English. Do you recommend full discharge from time to time to test battery capacity?

The biggest indicator that you have discharged too much will be heat, if your packs are getting hotter than normal, you are probably discharging them too low. 3.7 v/cell resting voltage (checked after the packs have cooled down) or 80% whichever comes first is also a good test but each brand and chemistry varies a bit. Discharging them deeper than that on a regular basis is probably going to take a bit of life off them.

If you want to check battery capacity, discharge to about 3.3V/cell. There is almost no capacity left after that anyways.

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Chad Northeast

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RE: Is 80% discharge safe for Li-Po batteries?? - 10/4/2006 4:28:45 PM

xalm04

Posts: 77
Joined: 9/13/2004
From: Quito, ECUADOR
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quote:

ORIGINAL: can773

The biggest indicator that you have discharged too much will be heat, if your packs are getting hotter than normal, you are probably discharging them too low. 3.7 v/cell resting voltage (checked after the packs have cooled down) or 80% whichever comes first is also a good test but each brand and chemistry varies a bit. Discharging them deeper than that on a regular basis is probably going to take a bit of life off them.

If you want to check battery capacity, discharge to about 3.3V/cell. There is almost no capacity left after that anyways.

Thanks Chad. I check battery condition after each flight and always I have 3.74 - 3.78 V per cell, so I believe I´m treating them well. I have read in some of your posts that you use batteries to 95% of their capacity, and notice almost no drop in performance. How many cycles do you have in those batteries?

I chose TP 4200 due to weight limitations, so that´s why I have to be very carefull on capacity usage, but after 34 flights I notice that at this altitude the capacity usage is lower than at sea level, maybe I have to switch to higher pitch props. Normally I´m using 2900 - 3200 mAh per P07 flight, in all wind conditions.

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Xavier Almeida

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