250 Brushless Motor Losing Power?

[Nari]

Hi everyone,

I'm new to this forum and hope you can guide me.

I have a WLtoys V912 (Brushless version) and had a crash with it.
I feel that it's main brushless motor is not as powerful as it used to be. It still works but doesn't rev as fast as before and the helicopter gains altitude slower. I checked the motor and the shaft seems OK and is not bent. It didn't overheat too. The motor is surrounded by two layers of solid aluminum parts and never hit anything during the crash.

This is a picture of the motor:



What do you think? Could it be the ESC too?

 

[Tony]

I'm thinking this issue is going to be the battery more than the ESC As batteries age, they sag in voltage as you are pulling power from them more than when they are new. However, this could also be solved by an ESC settings change in some cases. The ESC has what is called an LVC (Low Voltage Cutoff). This is there for lipo batteries to keep you from draining your batteries too far. The old battery could be sagging more than new batteries causing the ESC to hit the LVC causing the issue you are seeing now. If you can adjust the LVC, try setting it to 3.2 volts per cell and see if that helps. If not, I'm thinking a new battery may be in order.

 

[Nari]

Thanks for your advice Tony but I tried another battery and the problem still exists. Let me put it this way:
Before the crash it required about 50% throttle to keep hovering but now it needs about 70% throttle to hover at the same altitude.

This is the ESC:

 

[Tony]

Have you checked your throttle curve in your transmitter? I'm not sure you can change those, but if you can, on a fixed pitch helicopter, you want a linear throttle curve.

Another thing you can do is test that capacitor on the ESC. If the end is bulged out or you see something leaking from it, it's bad. If that is fine, and you can't adjust the LVC, you may need a new ESC, or even possibly the motor is damaged from an over current situation from a crash. Just reaching for solutions at this point.

 

[Nari]

I lent my friend's transmitter and tested the throttle but noticed no difference.

As you see in the picture, the ESC is hidden behind a cover and I can't see what's inside but I will tell you this. The ESC of this chopper is placed between the PCB and the battery and it must have been pressed between the two during the crash. But someone told me that a damaged ESC will not work at all.

 

[murankar]

I was just thinking about this. I didn't even see that tony posted already. I too am guessing batteries. If you have had these packs for a while then they may be dead. If they are fully charged and are losing power right away, my guess is the capacity is done or gone.

 

[Nari]

I'm sure it's not the battery pack because I tested other packs and it didn't solve the problem.
This problem happened only after 27 flights. I had a crash after 27th flight and this weird problem occurred.

 

[Tony]

Adjusting the ESC is actually done electronically. Can you post a picture of the label? I will see if I can find a way to adjust the settings in it. Nothing physical can be adjusted, only changes in the firmware.

 

[Nari]

It is a 20A ESC. I found these pictures of it:

 

[Tony]

Does it not have a label on it? If not, there is no way of knowing what brand it is or what firmware it has in it, and thus no way of knowing how to program it if it can even be programmed.

 

[Nari]

It doesn't mention any brand on it. Can I use other ESCs with 20A rating?

 

[Tony]

Maybe. That single wire has me scratching my head a little. I think it is just signal, but it is read which signifies power, but power is always in the center on most newer models and that one is on the end, making me think it is just a signal wire. If you do put another ESC on it, take out the positive and negative wire and tape them up and just leave the signal wire plugged in.

 

[Nari]

I forgot to say that I even lubricated the motor and it improved its performance just a little.
So, according to what you said the first thing to do is to find an ESC and replace it.

 

[Tony]

Instead of replacing parts, have you thought about going with something like the V911 helicopter? Still fixed pitch, and very easy to fly. I need to do a review on the one that was sent to me a while back. Great cheap replacement to the Blade mSR that I learned how to fly on.

US$33.99 32% WLtoys V911-pro V911-V2 2.4G 4CH RC Helicopter RC Toys & Hobbies from Toys Hobbies and Robot on banggood.com

Edit: I just now looked and saw that you have a V912. The link above would actually be a downgrade, but could get you in the air. Below is a link to the V912 BNF since you already have a transmitter to use. Save you a little money anyway.

US$41.99 15% Large WLtoys V912 4CH RC Helicopter With Gyro BNF RC Toys & Hobbies from Toys Hobbies and Robot on banggood.com

 

[Nari]

I have both V911 & V912 but V911 is only good for indoor flight. V912 can withstand wind much better.

US$41.99 15% Large WLtoys V912 4CH RC Helicopter With Gyro BNF RC Toys & Hobbies from Toys Hobbies and Robot on banggood.com

That's the brushed version of V912. The BNF brushless version is 20k more expensive.

I really enjoy disassembling and replacing parts. I like to restore broken things. It is not only more cost-effective but also more informative. I disassembled my V912 after crash. I'm a DIY man!



I even removed my car's alternator myself and repaired it which includes removing the whole throttle body, intake manifold, oil vapor hoses and fuel rail + alternator belt and idlers!

 

[Nari]

Dear friends,

My brushed V912 has a problem. It's throttle response is NOT linear and progressive.

When I give it throttle (even near full throttle), it revs up a little and then after 2 seconds it suddenly revs up quite fast! This hesitation is really annoying and makes it uncontrollable at times. It is hard to keep it hovering because it either wants to gain or lose altitude.

In short, there is no correlation between the amount of throttle input and output. For example, if I give it 30% throttle it reacts with 70% and vice versa.

I have to add that I replaced the PCB but that didn't solve the problem.
What could be the reason?

Anyone can help?

 

[Tony]

That could be a worn out pot in the Tx giving the wrong values. I'm not sure if you can calibrate that ESC with the Tx, but if you can, you might try that.

 

[Nari]

That could be a worn out pot in the Tx giving the wrong values. I'm not sure if you can calibrate that ESC with the Tx, but if you can, you might try that.

Thanks again for your help Tony.

This time it is my BRUSHED V912 not brushless one. It doesn't have an ESC.
I should test it with another transmitter but could it be the main motor itself which is faulty?

 

[Tony]

Brushed motors have an ESC just like brushless. Only difference is brushless is 3 phase.

 

[Nari]

Really? I didn't know it. Where is the ESC of my brushed V912? Is it inside the transmitter?
I don't see any ESC inside the helicopter.