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Old Jan 09, 2013, 09:19 AM
Rockin' & Flyin'
Saxguy1000's Avatar
Virginia Beach
Joined Dec 2009
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I'll send you the Excel sheet! See your pm.
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Old Jan 09, 2013, 10:50 AM
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DaveNH's Avatar
United States, NH
Joined Nov 2012
72 Posts
Quote:
Originally Posted by 1Pilgrim View Post
I would appreciate hearing how accurately the equation predicts your battery's performance.
Assuming my charger readings (Thunder AC6) are accurate, the formula and what it reports are pretty far off. (#1, and # 2&3 are 2 different batteries)
Might be the charger, even it's reading don't seem consistent, it shows the battery at 3.78v remaining took more than the one that was at 3.76v, I would thing it would take less?

1. 3.78v, sheet predicted 296.98mAh, charger indicated it supplied 380mAh
2. 3.76v, sheet predicted 324.94mAh, charger indicated it supplied 370mAh
3. 3.74v, sheet predicted 351.44mAh, charger indicated it supplied 423mAh
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Old Jan 09, 2013, 11:14 AM
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United States, CO, Longmont
Joined Jan 2013
67 Posts
I broke a ball of the swashplate when trying to remove link, the tail rotor and fin aren't looking so hot either, sheesh.

Can anyone recommend a good source for spare 120 SR parts?
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Old Jan 09, 2013, 11:39 AM
Rockin' & Flyin'
Saxguy1000's Avatar
Virginia Beach
Joined Dec 2009
2,817 Posts
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Originally Posted by dferrey View Post
I broke a ball of the swashplate when trying to remove link, the tail rotor and fin aren't looking so hot either, sheesh.

Can anyone recommend a good source for spare 120 SR parts?
The cheapest with shipping price you can get on eBay. HopMeUp out of NC is usually the cheapest for me, but I live in a neighboring state.
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Old Jan 09, 2013, 11:43 AM
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United States, CO, Longmont
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Originally Posted by Saxguy1000 View Post
The cheapest with shipping price you can get on eBay. HopMeUp out of NC is usually the cheapest for me, but I live in a neighboring state.
Thanks, funny, I've just been looking at HopMeUp and yeah, the prices look very good.
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Old Jan 09, 2013, 11:54 AM
Rockin' & Flyin'
Saxguy1000's Avatar
Virginia Beach
Joined Dec 2009
2,817 Posts
Quote:
Originally Posted by DaveNH View Post
Assuming my charger readings (Thunder AC6) are accurate, the formula and what it reports are pretty far off. (#1, and # 2&3 are 2 different batteries)
Might be the charger, even it's reading don't seem consistent, it shows the battery at 3.78v remaining took more than the one that was at 3.76v, I would thing it would take less?

1. 3.78v, sheet predicted 296.98mAh, charger indicated it supplied 380mAh
2. 3.76v, sheet predicted 324.94mAh, charger indicated it supplied 370mAh
3. 3.74v, sheet predicted 351.44mAh, charger indicated it supplied 423mAh
The problem may be that it's hard to tell how full it is even after it registers 4.2. As I'm charging, the battery will go up to 4.2 quickly, but the mah are continually loaded long after it reached the voltage max. It also would vary depending on how long the battery sat before using and the temperature outside. Interesting, though.
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Old Jan 09, 2013, 12:05 PM
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United States, NH
Joined Nov 2012
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Originally Posted by Saxguy1000 View Post
The problem may be that it's hard to tell how full it is even after it registers 4.2. As I'm charging, the battery will go up to 4.2 quickly, but the mah are continually loaded long after it reached the voltage max. It also would vary depending on how long the battery sat before using and the temperature outside. Interesting, though.
We might be trying to put a specific number on something that is just to much of a variable.
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Old Jan 09, 2013, 01:34 PM
Look ma, no hands!
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United States, WI, Sheboygan
Joined Aug 2011
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Quote:
Originally Posted by DaveNH View Post
We might be trying to put a specific number on something that is just to much of a variable.
Granted, but comparing actual to predicted on 435 flights I only found a half dozen "outliers" i.e. predicted values that were more than 5% off. I could account for at least a couple of the outliers; there were times when I interrupted the charging cycle (lower mAh "put back") or charged at a slow rate for the entire charging cycle (higher mAh "put back").

I also had batteries that were well managed, i.e. almost never discharged too far, allowed to cool to ambient before charging and never recharged too fast.

I agree that this whole exercise may be purely academic anyway. The closer a battery is to fully charged or fully discharged the less accurate the predicted "put back" will be, but why bother to charge if the battery is near full and why wait to charge until the battery is near empty? Just use a timer and bypass the algebra.
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Old Jan 09, 2013, 01:48 PM
NotAnotherMomentLostToSei zures
Chap1012's Avatar
United States, MA, Malden
Joined Mar 2008
11,115 Posts
80% Rule=Fun. It doesn't get any easier

This will be my last post on the subject....*YAY*
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Old Jan 09, 2013, 01:54 PM
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United States, NH
Joined Nov 2012
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Quote:
Originally Posted by 1Pilgrim View Post
Just use a timer and bypass the algebra.
My mathematically challenged brain thinks this is the best idea yet
But I do like to somewhat understand the technology I'm working with, and how to prolong its life and not treat it poorly, and with lipos, treating them badly usually doesn't end well.
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Old Jan 09, 2013, 02:11 PM
Look ma, no hands!
1Pilgrim's Avatar
United States, WI, Sheboygan
Joined Aug 2011
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Originally Posted by Chap1012 View Post
80% Rule=Fun. It doesn't get any easier

This will be my last post on the subject....*YAY*
"YAY" indeed!
Rule #2 Never leave well enough alone!
Rule #3 Why use one syllable/word/sentence/paragraph when three will do?
Rule #4 If it ain't broke, break it!
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Old Jan 09, 2013, 04:29 PM
Rockin' & Flyin'
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Virginia Beach
Joined Dec 2009
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Break it... Yes--my credo.
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Old Jan 09, 2013, 04:46 PM
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United States, CO, Longmont
Joined Jan 2013
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Originally Posted by Saxguy1000 View Post
Break it... Yes--my credo.
If by credo you mean the results of my "skillful" flying technique, then, yeah, that's my credo as well .
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Old Jan 09, 2013, 06:20 PM
Heli's rule!
dacaur's Avatar
Midvale, Utah, USA
Joined Mar 2005
8,624 Posts
The problem with your formula 1Pilgrim, is that its plotted based on your batteries and your heli, at your altitude. Different helicopters (some will draw more amps, asome less, depending on how new the motor is and other variables like lubrication, etc), at different altitudes are going to have different amp draws, (it takes more power to fly at higher altitudes) so the formula is going to be off for anyone but you. I guess someone at the same altitude might get close, but again, a worn motor or warped rotor could easily throw it off. When you batteries degrade a little more, or you replace your motor, or go on vation to a different altitude, your formula will not be as close any longer....

Thats the problem with creating a formula based on a set of data, because if the data changes, the formula no longer works.

Math hurts my brain anyway, I'll just set a timer and let my charger decide how much power to put in my batteries...
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Old Jan 09, 2013, 08:26 PM
Look ma, no hands!
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United States, WI, Sheboygan
Joined Aug 2011
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Originally Posted by dacaur View Post
The problem with your formula 1Pilgrim, is that its plotted based on your batteries and your heli, at your altitude.
As I said, this is really an academic exercise; like Mike said I time my flights and just go fly. I did make a point of mentioning the type and condition of my batteries and the management principles I follow. I also asked for feedback from other pilots so I can find out the extent to which the variables you mention affect the formula. It gives me something to do on these long winter nights!
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Last edited by 1Pilgrim; Jan 09, 2013 at 08:41 PM.
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