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Old Oct 13, 2014, 02:58 PM
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Question
Lipo battery capacity rises 1/2 hour after use

Hi,

I have a Zippy compact 1000mah 25C LIPO and using a Hobbyking Cellmate 7 to check the battery level right after use on foamie trainer aircraft. The plane has a an turnigy 1100kv motor (max current is 18A) - most of the time I'm around half throttle.

Right after 10 minutes of use I check the battery level and the reading shows 14%. Half hour later I check it again and I notice the capacity is 29%.

The battery does not seem to be puffed, never felt is was hot.

Is it normal for a lipo battery's capacity level to rise afterwards?

Thanks!



Thanks.
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Old Oct 13, 2014, 03:04 PM
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Florida
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Yes, it is normal. After disconnecting from use and left to rest a few minutes, the open circuit voltage will increase a bit.
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Old Oct 13, 2014, 03:04 PM
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The capacity doesn't really rise but the voltage does and since the capacity reading is derived from the voltage reading, it appears to rise.
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Old Oct 13, 2014, 06:06 PM
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Thanks!
The LIPO is 3S for 11.1 Volts. When fully charged the voltage reading is 12.6 volts. How low can voltage go before I stop using it? Is the safe threshold 11.1 V or can it go even lower.
I've read elsewhere safe theshold is no less that 11.1 V since that is 3.7 V / cell. But the voltage cut off in the ESC is often times less 3.7 V / cell.
With the ESC I'm using the low voltage threshold can be set to low / high - both of these setting are less than 3.7 V / cell. So that leads me to believe the low voltage threshold is even lower than that.
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Old Oct 13, 2014, 06:37 PM
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For maximum life, you shouldn't go below about 11.2V resting voltage, which is the voltage you measure after the battery has had a few minutes to recover. The minimum voltage under load will depend on the internal resistance of the cells and the amp draw of the motor.
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Old Oct 13, 2014, 08:57 PM
Space Coast USA
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Quote:
Originally Posted by dropout View Post
Thanks!
The LIPO is 3S for 11.1 Volts. When fully charged the voltage reading is 12.6 volts. How low can voltage go before I stop using it? Is the safe threshold 11.1 V or can it go even lower.
.
Set the LVC at a voltage that leaves your pack at 3.7+V/cell after landing and disconnected. It probably will be anywhere between 3.0 and 3.4V. Depends on the C-rate draw of your setup. The higher the C-rate draw the lower the pack voltage will drop during discharge and the more it will rebound after landing. There is no "one LVC setting" for all applications.
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Old Oct 14, 2014, 12:41 AM
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Quote:
Originally Posted by hoppy View Post
Set the LVC at a voltage that leaves your pack at 3.7+V/cell after landing and disconnected. It probably will be anywhere between 3.0 and 3.4V. Depends on the C-rate draw of your setup. The higher the C-rate draw the lower the pack voltage will drop during discharge and the more it will rebound after landing. There is no "one LVC setting" for all applications.
Hoppy I just bought a HK low voltage alarm which goes off quite loud at 3.3 volts. I thought this was a little low but maybe it's set just right if the voltage will rise afterwards.

Pat
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Old Oct 14, 2014, 01:02 PM
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The voltage will absolutely rise afterwards.
After that alarm goes off, what is the voltage of the pack 5 min after disconnecting it from the plane? Anything over 3.7V/cell is OK.
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Old Oct 14, 2014, 01:22 PM
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Hoppy I haven't tried it in the plane yet. I've only connected it to check it out. A lot of reviewers said the cut out voltage of 3.3 was too low but if it settles at around 3.7 then that's fine. 😁
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Old Oct 14, 2014, 04:31 PM
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That's correct.
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Old Oct 15, 2014, 03:13 AM
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United States, MI, Grand Rapids
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Quote:
Originally Posted by coongoola View Post
Hoppy I haven't tried it in the plane yet. I've only connected it to check it out. A lot of reviewers said the cut out voltage of 3.3 was too low but if it settles at around 3.7 then that's fine. 😁
Check your documentation on the tester/alarm, the ones I have can be set to 0ff...or 2.7v-3.8v, maybe your alarm voltage can be set to...
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Old Oct 15, 2014, 03:19 AM
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Originally Posted by brentg View Post
Check your documentation on the tester/alarm, the ones I have can be set to 0ff...or 2.7v-3.8v, maybe your alarm voltage can be set to...
Brent this is only a cheap HK unit... nothing fancy at all, and I'm pretty sure that you can't change the voltage cutout. It seems fixed at 3.3v.

Pat
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Old Oct 15, 2014, 04:40 AM
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Oh ok, I thought you had the HK /GT clone cell check/alarm..
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