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Old Aug 19, 2013, 07:01 PM
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PiperRon's Avatar
Joined Feb 2013
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How Much Battery Do you Use; Flight Time

I fly mostly 3s 2200 batteries. 30C. I normally fly them down to about 11.5volts or about 3.80 per cell. Some at the field say I can go down to 10.5volts. I get about 7.5 minute flights with various throttle settings.

How far down do you drain your batteries.??

EDIT; I just found another thread containing the same sort of question. Reply here if you wish.
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Last edited by PiperRon; Aug 19, 2013 at 07:08 PM.
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Old Aug 19, 2013, 08:11 PM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,209 Posts
Same as you.

Some don't know what they're talking about.

mw
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Old Aug 19, 2013, 08:11 PM
Dude, I do fly all day long!
rcalldaylong's Avatar
San Jose, California
Joined Dec 2007
5,825 Posts
Quote:
Originally Posted by PiperRon View Post
I fly mostly 3s 2200 batteries. 30C. I normally fly them down to about 11.5volts or about 3.80 per cell. Some at the field say I can go down to 10.5volts. I get about 7.5 minute flights with various throttle settings.

How far down do you drain your batteries.??

EDIT; I just found another thread containing the same sort of question. Reply here if you wish.
Yep. many many threads on this already.

10.5v is too low. You should go no lower than 11.1 or 3.7v/cell resting voltage.
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Old Aug 19, 2013, 08:34 PM
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1320fastback's Avatar
USA, CA, Oceanside
Joined Jul 2008
3,228 Posts
I try to fly to where they come down near storage voltage.. Give them a simple balance and pack them away.

If you want to fly longer just get more batteries. With what they cost now days theirs not really any reason to deplete them.
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Old Aug 20, 2013, 08:01 AM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,214 Posts
Hello!

I've already said it, and I'll say it again:

Judging the capacity by voltage is a problematic thing. The voltage does not only depend on the remaining capacity, but also on the load, the IR of the battery pack, it's temperature and so on.
You'll never get anything accurate here.

The resting voltage might be a better approach, but this way, you'll always have to stop the motor. Try this with a heli- or multicopter.

I've always said that the best way to determine the capacity is to use telemetry with a capacity sensor.

I'm doing this since 2008, and it is truly fantastic.
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Old Aug 20, 2013, 09:19 AM
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New Zealand, Canterbury, Christchurch
Joined Jun 2013
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Try to go for 3.7 resting, if they end up below 3.6 it's time to think about turning the timer back a little or easing up on the collective.
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Old Aug 20, 2013, 09:49 AM
Registered User
United States, WI, Slinger
Joined Mar 2006
489 Posts
Quote:
Originally Posted by Julez View Post
Hello!

I've already said it, and I'll say it again:

Judging the capacity by voltage is a problematic thing. The voltage does not only depend on the remaining capacity, but also on the load, the IR of the battery pack, it's temperature and so on.
You'll never get anything accurate here.

The resting voltage might be a better approach, but this way, you'll always have to stop the motor. Try this with a heli- or multicopter.

I've always said that the best way to determine the capacity is to use telemetry with a capacity sensor.

I'm doing this since 2008, and it is truly fantastic.
You don't need telemetry, that's overkill big time. I often use my EagleTree Systems data logger to get a feel for the current draw and after that it's fly, charge, check how much goes back in, repeat. If you want to make it overly complicated that's your right. I've been flying electrics for 30 years and I firmly believe in the KISS philosophy, Keep It Simple Stupid.


Mike
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Old Aug 22, 2013, 06:30 AM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,214 Posts
Quote:
get a feel for the current draw and after that it's fly, charge, check how much goes back in, repeat.
I learned never to rely on feelings. The problem with your setup is, you know how much capacity was used only after you landed.
If you got your feeling wrong, it might not be beneficial for the life of you battery pack. And if you change the prop, timing, or motor, you have to check things all over again.

This is like judging one's speed by the amount of speeding tickets one gets. I prefer to have a speedometer.

Telemetry means for me that I plug a $20 sensor between the pack and the esc. No other expenses or additional devices needed. As a result, I get accurate readings of the used capacity right on my transmitter screen. No mor guessing or wondering how much might have been used, no more testing and logging. Just flying with the pleasant feeling that everything is alright, and land when the 80% alarm goes off. It's that simple.
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Last edited by Julez; Aug 22, 2013 at 06:38 AM.
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Old Aug 22, 2013, 02:18 PM
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ggcrandall1's Avatar
USA, GA, Marietta
Joined Aug 2005
5,557 Posts
Julez,
What transmitter are you using?
Glen
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