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Oct 06, 2017, 07:46 PM
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After watching the 2S performance in the video I have to question why anyone would want to go to 3S other than possibly propping down for lower amp draw and longer flight time (that the extra weight will likely negate). 3S speed on the stock motors (if they survive)/props would probably tax the airframe to the point of needing reinforcement and again, added weight. Maybe I'm wrong on 3S and I hope I am but from what I see in the video I think I'll be quite happy with an out of the box airplane on 2S.

Joe
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Oct 06, 2017, 11:24 PM
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Quote:
Originally Posted by JohnM
Have you tried flying for an additional 2 minutes and then check the resting voltage (after 30 seconds)? If so what was it?
I flew it tonight for 9.25 minutes. The measured voltage was 7.5v and it only took 197mAH on recharging. Is this an indication that the capacity of the battery is becoming less than the claimed 450mAH?

I'll keep extending the time and measuring the voltage/mAH and see what shakes out. How low on the voltage should I go before I quit extending the time?
Oct 06, 2017, 11:43 PM
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Rampage's Avatar
Quote:
Originally Posted by turbojoe
After watching the 2S performance in the video I have to question why anyone would want to go to 3S other than possibly propping down for lower amp draw and longer flight time (that the extra weight will likely negate). 3S speed on the stock motors (if they survive)/props would probably tax the airframe to the point of needing reinforcement and again, added weight. Maybe I'm wrong on 3S and I hope I am but from what I see in the video I think I'll be quite happy with an out of the box airplane on 2S.

Joe
Mostly because I've already got a ton of 3S 480s and 500s from my Viking.
Oct 07, 2017, 12:30 AM
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bhoov128's Avatar
Quote:
Originally Posted by beqok
I flew it tonight for 9.25 minutes. The measured voltage was 7.5v and it only took 197mAH on recharging. Is this an indication that the capacity of the battery is becoming less than the claimed 450mAH?

I'll keep extending the time and measuring the voltage/mAH and see what shakes out. How low on the voltage should I go before I quit extending the time?
If your charger is correct on how much you "put back in" i.e. 197mAh, then you should be getting over 16 minute flight times with that 450....

Pretty easy to extrapolate the timer; it's

( (actual flight time in seconds) * (80% of battery capacity ) ) / (actual mAh recharged)

For your example

(555*360)/197 = ~ 16.9 minutes
Oct 07, 2017, 03:00 AM
I'd rather be flying!
turboparker's Avatar
Quote:
Originally Posted by beqok
I flew it tonight for 9.25 minutes. The measured voltage was 7.5v and it only took 197mAH on recharging. Is this an indication that the capacity of the battery is becoming less than the claimed 450mAH?

I'll keep extending the time and measuring the voltage/mAH and see what shakes out. How low on the voltage should I go before I quit extending the time?
Increase your flight time until you reach the 80% discharge point as measured by how many mAh it takes to recharge. The minimum voltage for LiPos is 3.3V/cell. Anything lower than that will kill the pack in short order, if done more than once or twice. If the rest voltage is under 3.3V/cell after flying to the 80% discharge point, your pack is either shot or it's just a crappy pack. If the plane hits LVC (motor pulsing) before you reach the 80% discharge point, your pack is really saggy under load. If it's relatively fresh, then it's a crappy pack. If it's old and/or has a fair number of cycles on it, then it's starting to fade away.

Joel
Latest blog entry: E-flite 850mm Pitts
Oct 07, 2017, 03:07 AM
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microheli's Avatar
Quote:
Originally Posted by beqok
I flew it tonight for 9.25 minutes. The measured voltage was 7.5v and it only took 197mAH on recharging. Is this an indication that the capacity of the battery is becoming less than the claimed 450mAH?
Yes if the measurements are accurate. 197mah is less than 50% and should in any case over 7.6V.
And you should measure any cell independent because 7.5V can be 3,75V and 3,75V (about 25% left) or 3.8V and 3.7V (50% and 10% left) and the indication of one weak cell.
Quote:
I'll keep extending the time and measuring the voltage/mAH and see what shakes out. How low on the voltage should I go before I quit extending the time?
Make sure that no cell go under 3.7V
Oct 07, 2017, 03:25 AM
I'd rather be flying!
turboparker's Avatar
Quote:
Originally Posted by microheli
....Make sure that no cell go under 3.7V
The safe discharge voltage for LiPos is 3.3V/cell. If you only fly to 3.7V/cell, you're no where near close to an actual 80% discharge.

Joel
Latest blog entry: E-flite 850mm Pitts
Oct 07, 2017, 03:44 AM
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microheli's Avatar
Quote:
Originally Posted by turboparker
Increase your flight time until you reach the 80% discharge point as measured by how many mAh it takes to recharge. The minimum voltage for LiPos is 3.3V/cell. Anything lower than that will kill the pack in short order, if done more than once or twice.
Yes but this is the voltage under load and impossible to measure if you not have telemetry which this brick not have. A no load voltage of 3.7V is good value to stop flying and come much earlier than the LVC (pulsing motor) with damage the battery more or less and is only the last protection and should avoided. A 450mah battery in this application even with full throttle is only a load of 6C and the most actual batteries are very deep discharged when they reach the 3.3V LVC value.
Oct 07, 2017, 03:47 AM
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microheli's Avatar
Quote:
Originally Posted by turboparker
The safe discharge voltage for LiPos is 3.3V/cell. If you only fly to 3.7V/cell, you're no where near close to an actual 80% discharge.
This mean the voltage with no load that he measured and 3.7V with no load is near and mostly under 80% discharge.
Last edited by microheli; Oct 07, 2017 at 03:54 AM.
Oct 07, 2017, 08:52 AM
**I'm Battman**
RCBABBEL's Avatar
Chris explains it in further detail...
http://www.tjinguytech.com/charging-how-tos/80-rule

Roger
Oct 07, 2017, 03:08 PM
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bhoov128's Avatar
Quote:
Originally Posted by RCBABBEL
Chris explains it in further detail...
http://www.tjinguytech.com/charging-how-tos/80-rule

Roger
Thats a lotta words to get to the pretty simple formula I posted
Oct 07, 2017, 03:32 PM
I'd rather be flying!
turboparker's Avatar
Quote:
Originally Posted by RCBABBEL
Chris explains it in further detail...

Roger
Yup!

As he notes - one should never rely on voltage to determine LiPo discharge-depth, as it is HIGHLY inaccurate & varies GREATLY between packs. The ONLY true measure of discharge-depth is to go by how many mAh it takes to recharge, divided by pack capacity.

I've been going by the 80% rule as measured above ever since I started flying electrics a decade ago. I always get 300+ cycles from my Hyperion & TP packs, and I charge them @ 5C.

Joel
Last edited by turboparker; Oct 07, 2017 at 03:41 PM.
Oct 09, 2017, 05:16 AM
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Oct 09, 2017, 09:10 AM
**I'm Battman**
RCBABBEL's Avatar

3s


Quote:
Originally Posted by turbojoe
After watching the 2S performance in the video I have to question why anyone would want to go to 3S other than possibly propping down for lower amp draw and longer flight time (that the extra weight will likely negate). 3S speed on the stock motors (if they survive)/props would probably tax the airframe to the point of needing reinforcement and again, added weight. Maybe I'm wrong on 3S and I hope I am but from what I see in the video I think I'll be quite happy with an out of the box airplane on 2S.

Joe
---

Joe,

I've been thinking about your Q over the weekend.
My answer is simple.
It's all about performance!

The awesome thing is...
Almost all of the UMX airframes can handle the added power.
Many require no mods at all.
I do everything I can to not add weight to my planes.
Some of the early UMX planes needed a cf rod added the the horizontal stab.
Horizon has since added that.

I also add as little batt weight as possible.
That's why I mostly fly 3S 120s & 180s.
2S 330: 17g
3S 180: 18g
I trade flight time for killer performance!

I love how these UMX planes fly on max throws w/max power!!

Roger
Oct 09, 2017, 12:27 PM
**I'm Battman**
RCBABBEL's Avatar
Fly How You Want To Fly

HH email title today.

I say, Amen brother!!

Roger


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