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Deterioration in Power — ESC?

Old 11-03-2018, 11:10 AM
  #1  
DarZeelon
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Default Deterioration in Power — ESC?

I have a CN BestOne 25A Guard ESC in my Hummer model.
It is identical for all practical purposes to old Turnigy Sentry 25A item.

It has an extra connector to sense per-cell voltage (to extend the useful life of LiPo packs that will be connected to it, by cutting power before the weakest cell falls...).

This item has been in use since 2007 or 2008, but was not used over about eight years of that time span. It has a total of about 25-30 hours on it, powering a 900 kV motor + 1000mAh 3S pack, spinning a 10x3.8 SF prop (also tried with 11x3.8 in the beginning).

The previous model (MS Composit Unique) used to easily hover at about 1/2 throttle, with plenty of extra power to launch out. But the current model, that does not seem to be appreciably heavier, needs full throttle just to hover, making 3D performance rather lacking.


I used a Watt's Up and with a 90% full pack it registered 12.2A and 130W.

Will ESCs naturally age and deteriorate in use over time, or in storage; or is the motor the culprit?
Will the magnets in the motor weaken over time?


Dar Zeelon

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Old 11-03-2018, 02:34 PM
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ron_van_sommeren
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Originally Posted by DarZeelon View Post
... Will the magnets in the motor weaken over time? ...
No, unless they get overheated, resulting in higher Kv.
  1. Overheating magnets causes de-magnetizing (irreversible! ), which in turn results in higher Kv. Motorcurrent is proportional to Kv³ , and resistance losses in the copperwire are proportional to current². Therefore resistance losses are proportional to Kv⁶!!!
  2. Higher current → hotter motor → weaker magnets → higher Kv → higher current → hotter motor → weaker magnets → higher Kv → higher current ⟲⟲⟲ etcetera etcetera, temperature runaway, major conflagration
  3. Determining whether magnets still have original strength, by determining whether Kv motor parameter (in rpm/volt) is still the same, several simple straightforward methods.
    www.bavaria-direct.co.za → motor constants
  4. Generator test, only using a power drill and a voltmeter
    (Re)winding and building motors - RCG (sticky) → opening post → #40 Generator test
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Old 11-03-2018, 02:39 PM
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Originally Posted by DarZeelon View Post
... Will ESCs naturally age and deteriorate in use over time, or in storage ...
No. If this were the case, it would overheat instantly.
What was battery no-load voltage after charge, and battery voltage sag at wide open throttle?
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Old 11-03-2018, 06:08 PM
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Originally Posted by DarZeelon View Post
I have a CN BestOne 25A Guard ESC in my Hummer model.
It is identical for all practical purposes to old Turnigy Sentry 25A item.

It has an extra connector to sense per-cell voltage (to extend the useful life of LiPo packs that will be connected to it, by cutting power before the weakest cell falls...).

This item has been in use since 2007 or 2008, but was not used over about eight years of that time span. It has a total of about 25-30 hours on it, powering a 900 kV motor + 1000mAh 3S pack, spinning a 10x3.8 SF prop (also tried with 11x3.8 in the beginning).

The previous model (MS Composit Unique) used to easily hover at about 1/2 throttle, with plenty of extra power to launch out. But the current model, that does not seem to be appreciably heavier, needs full throttle just to hover, making 3D performance rather lacking.


I used a Watt's Up and with a 90% full pack it registered 12.2A and 130W.

Will ESCs naturally age and deteriorate in use over time, or in storage; or is the motor the culprit?
Will the magnets in the motor weaken over time?


Dar Zeelon

Well all good from Ron ... but I would like to comment as a Hummer Flyer ...

1. The prop you are using will need high RPM to do anything with a Hummer.
2. A 900kv motor ? That means with your prop - you will have that throttle at high level to get hover etc.

Put both together and that means a lot of throttle needed ...

My setup (two Hummers) ... Turnigy 2836 1100kv, 11x5.5E prop, 30A ESC ... she then hovers on about 60% throttle. With unlimited vertical.

Nigel

Last edited by solentlife; 11-03-2018 at 08:41 PM.
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Old 11-03-2018, 08:07 PM
  #5  
DarZeelon
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Default Motor in Hummer

Thank you Nigel and Ron for your replies.

So, I will add that none of the equipment ever overheated...
The KEDA 920kV motor is still shiny blue.

The ESC was never more than warm to the touch, as were the battery packs after flight.

Because this Hummer and the now defunct Unique are so closely matched in size, I thought the power-set will work similarly in the new, as it did in the old.

I am much less of an expert in e-flight...
So, would everything change for the better (thrust-wise) if I just switch to the 11x3.8 SF prop? I know it will slow even more...

I do understand that speed will be much improved with the 10x4.7 SF, but will thrust (with the identical disk-area).

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Old 11-03-2018, 08:48 PM
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Slow fly are in my honest opinion crap !! If you fly slow, not much power ... then OK ... but in 3D work - you can hear a SF prop cry out in pain when you flip / punch out ... its a WOMP sound ...

Forget the specs HK give for the Hummer ... you need an 11" prop and reasonable pitch ... as i mentioned - the 11x5.5E prop is superb match for the Hummer ... with the 2836 motor - you have all the grunt you can wish for.



Video of just having a bit of fun ... but basically it shows the amount of grunt ... all the video is in the 40 - 70% throttle range ...

Nigel
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Old 11-04-2018, 03:58 AM
  #7  
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I assume you know your battery is good; that it is capable of putting out more amps with little or no voltage sag.

Then I would recalibrate your ESC. Many ESCs will recalibrate by powering the model with the throttle at max and then back to zero to arm the ESC. I have a couple ESCs that seem to lose calibration but recalibrating brings them back.
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Old 11-04-2018, 05:06 AM
  #8  
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As suggested just above, try calibrating the ESC to the throttle on your radio. Use these steps:

1. Turn on your radio and move the throttle stick to full.
2. Plug the lipo into the ESC.
3. Depending on the ESC, you may hear two long beeps, then two short beeps. Immediately after the two short beeps move the throttle stick to off.

What this does is calibrates your ESC throttle endpoints to your throttle stick endpoints. I suspect right now it is not calibrated and you are not seeing full throttle at the ESC. I do this process for all of my ESCs the first time I plug them in.
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Old 11-05-2018, 05:09 AM
  #9  
DarZeelon
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Default Power...

Nice flying, Nigel!

...Although the sound truly is rather intrusive...


Pat, I re-calibrated the throttle using the method outlined in the HK web site.
It is not unlike what you wrote.

There is change.

In the previous test I used a nearly full pack (charged to 4.15V per cell), and got 12.2A at full throttle.
Now I used a pack charged for storage (3.84V per cell), and got 13.3A!

It is definitely perceptible!


But now the bad news...
I weighed the Hummer and it weighs... rapid drumbeats... 624 grams AUW with a battery pack!!


Pig!!

I never weighed the Unique, thinking about it... But this is definitely on the heavy side and uses the same power system.
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Old 11-05-2018, 09:24 AM
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solentlife
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I cannot remember exactly what mine weighed .. but probably not far of same.

That is why I recc'd the 2836 motor instead of the commonly used 2830.

The Hummer is a very good 3D machine ...

Nigel
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Old 11-05-2018, 10:43 AM
  #11  
DarZeelon
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Originally Posted by solentlife View Post
I cannot remember exactly what mine weighed .. but probably not far of same.

That is why I recc'd the 2836 motor instead of the commonly used 2830.

The Hummer is a very good 3D machine ...

Nigel

Thank you, Nigel.


This machine's stated flying weight (i.e. incuding 1000-1300mAh Lipo pack) is 450-500 grams...

I am quite positive the glues I put the model togather with, could not possibly weigh in at 124 grams, or even much, much more...
...and as I wrote, the LiPo I use is the lighter 1.0Ah item...


As to using an 11" prop; I fly ROG off a Kurkar field, smoothened but with small stones.
It quickly damages the 10" prop, so an even larger one would be rather useless. I cannot change to 3" wheels...

And for this purpose, the less effective HK SF series props, are cheap enough to replace every few flights... The APC E-Series props are damn expensive!


Last edited by DarZeelon; 11-06-2018 at 11:58 AM. Reason: Adding info...
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Old 11-06-2018, 05:08 PM
  #12  
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Nigel,


May I request that you please weigh your Hummer and post it here?

I don't think I have anything in mine that could explain why it is overweight...
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Old 11-07-2018, 09:00 AM
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solentlife
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Props ... I use the Hobby King APC 'type' and rarely break one .....

As to RoG .... I always hand launch anyway.

My Hummer is stripped of gear as its all in my MXS now ... But once I get back home .. I will check out the weight.

Nigel
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Old 11-07-2018, 06:56 PM
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Nigel,


I also transferred to the Hummer, most of the gear (motor, two of the servos, Rx, extensions, ESC, LiPos) from the now defunct MS Composit Unique.

The SF props don't often "break", but their blades' leading edges quickly become chipped and deformed; making them noticeably less effective in producing thrust.

The 'APC Type' props from HK (actually Aerostar)... I have one 9x4 size — too small.
And its translucent edges seem vulnerable to the same type of damage as the SF.
Getting some of the right size would probably take 6 weeks now.

Last edited by DarZeelon; 11-09-2018 at 08:14 AM. Reason: Clarification...
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Old 11-08-2018, 08:51 AM
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Here's my thread on the Hummer ... reading through gives me 635gr to fly.

https://www.wattflyer.com/forums/sho...=Hummer&page=2

Nigel
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Old 01-12-2019, 10:37 AM
  #16  
DarZeelon
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Default Problem Solved...

Ron and Nigel,


I have replaced the Keda Motor 20L - 920 motor with a 2830-8 (1300 kV) motor.
I also replaced the HK 1000mAh 30C LiPos, with
1550mAh 45C Pulse Battery LiPos.

I needed their extra 40 grams to replace two of the three steel nuts that were required to balance the Hummer, so there is no weight difference, since the motor weighs the same.

Everything else; 25A ESC and even the SF 10x3.8 prop remain the same.


It really changed this model from the caterpillar it was into a genuine butterfly...
Top current draw by the motor is now 25.9A! That's some 290W!

I do need to use less throttle, since amperage exceeds the rating of the ESC... And it has become a wildcat that needs some getting used to...
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Old 01-12-2019, 11:23 AM
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Nice to hear you are sorted.

As I said - the Hummer is a good 3D machine and a great learner machine for it.

Nigel
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Old 01-12-2019, 04:13 PM
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ron_van_sommeren
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Originally Posted by DarZeelon View Post
... I have replaced the Keda Motor 20L - 920 motor with a 2830-8 (Kv = 1300 rpm/volt) motor. ...
Both current and power drawn are proportional to Kv³. Therefore even minor changes in Kv can have considerable effect.
Going from 920 to 1300rpm/volt, current and power want to increase by factor (1300/1920)³ = 3.2, 220% more! (ignoring voltage sag in battery and wires due to higher current).

The 'full' story:
Motorcurrent is proportional to pitch¹, voltage², Kv³ and diameter⁴.
Power-drawn is proportional to pitch¹, voltage³, Kv³ and diameter⁴.

Without the exponentation
extra current with one or two cells added, simple table

So, changes in setup (and lousy Kv specifications!) can have surprisingly considerable/huge effects.
E.g. doubling voltage will four(2²)fold current, doubling Kv will eight(2³)fold current, and doubling prop diameter will sixteen(2⁴)fold current.
Even a small 10% change/difference in Kv will already lead to a 30% difference in current.
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Old 01-12-2019, 04:13 PM
  #19  
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Originally Posted by DarZeelon View Post
... Top current draw by the motor is now 25.9A! That's some 290W! I do need to use less throttle, since amperage exceeds the rating of the ESC ...
If current at wide open throttle is too high for the controller then reducing throttle to get current below ESC max.current is not a good idea. Better prop down to get WOT current down.

In fact, it is even harder on ESC than to keep overamping at full throttle. Better to prop down.
See:
Prettig weekend Ron

Last edited by ron_van_sommeren; 01-13-2019 at 12:09 AM.
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Old 01-12-2019, 10:29 PM
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This is very enlightening, Ron!

If I prop down it will need to be to a 9" size, which will deter 3D flight capabilities of this model, which is intended precisely for this purpose (not just horsing around as we frequently do).
That, because I don't know of a 10" prop size with less pitch than the 3.8" that I now have.

I do, however, have on hand a similar, same make and type 30A ESC.
But, allowing use of full throttle safely, will shorten flight times, unless we throttle down...
This model is intended to fly more slowly; it is not a pylon racer!

I see why using part-throttle will eventually, potentially shorten the life of the ESC...
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Old 01-13-2019, 12:16 AM
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It is a good practice to have some headroom built in.
About derating motors, controllers, batteries, electronics in general:Prettig weekend Ron
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