Hello, I’m using an old power bank battery for LED panel with 166 LED. (The seller said it is 80w). This panel has 8 steps of brightness and can control by remote control. The strange thing I‘ve noticed is when I’m using it with decreased brightness, I hear the whining sound like a buzzer from the battery. But with full brightness , whining sound has gone. (You can see in my attachment video link ). I don’t know it’s dangerous or not and Why it is happening. Could you please someone explain me ?
Video link: https://youtube.com/shorts/h2ekFf_2nhM?feature=share

Thank you so much.

 

Sorry, I couldn't hear the buzzing in your video.
But it's likely coming from somewhere in the electronics, not the battery.

 

Sorry, I couldn't hear the buzzing in your video.
But it's likely coming from somewhere in the electronics, not the battery.

Sound is exactly what you hear when I bring my lavalier mic close to the battery Sir. (Sounds like “tweeeeeee”)
In he video, I also placed my microphone close to the led panel and you can see there is no sound.

Sorry, I couldn't hear the buzzing in your video.
But it's likely coming from somewhere in the electronics, not the battery.

 

probably the switching frequency of the led driver. If the switching frequency is in the audible range. When you have it at lower brightness the circuit turns on and off the led array with a particular duty cycle. 50% half brightness, for example. So it doesn't actually dim the leds, it turns them on and off so they're only on 50% of the time and our eyes even that out and tell us its dimmer when in reality its off for half the time.

 

I concur with @jiggermole. The sound will be an artifact of the PWM (Pulse Width Modulation) used to dim the panel. You can confirm this is happening by settings a low dim level and moving the panel or your head. You will see a trail of on-and-off LEDs instead of a solid line due to persistence of vision.

PWM works because the average current delivered to the LEDs is proportional to the duty cycle of the PWM waveform. The duty cycle is the amount of time the waveform (a square or pulse wave) is on vs. off. The frequency and amplitude of the waveform remain constant.

PWM is used in many places for control, both by its direct ability to vary the average current, and so power, to a load like an LED or motor, and as a signal to a separate control circuit to change some parameter. It is also the way that “throbbing” standby power LEDs is done, the PWM duty cycle is varied in a sinusoidal fashion causing the LED so slowly light up and fade.

 

What are the specs of your power bank? Is it really capable of 80W? That would be 16A at 5V or 6.7A at 12V. What voltage is it putting out and at what max current?

I agree that the sound is caused by PWM, but if it really comes from the power bank, it might be because you are over stressing it.

 

No one has mentioned the fact that a Lithium Ion battery is made using interleaved flexible separators. These will attract and repel each other as the power is switched on and off by the PWM controller.

 

No one has mentioned the fact that a Lithium Ion battery is made using interleaved flexible separators. These will attract and repel each other as the power is switched on and off by the PWM controller.

That sounds like a plausible reason for the buzzing and would be something good to know in future.

 

What are the specs of your power bank? Is it really capable of 80W? That would be 16A at 5V or 6.7A at 12V. What voltage is it putting out and at what max current?

I agree that the sound is caused by PWM, but if it really comes from the power bank, it might be because you are over stressing it.

I’m not using a powerbank to power the led, I’m just using an old 10000 mah battery what I got from old powerbank. All I really wanna know is how li ion battery making sound.

For example, If I suddenly kicks a cat, it may make “meowww” painful sound comes from it’s mouth because of pain.

And now the answer I wonder is
how a Li ion battery making sound because of PWM?

Thank you so much.

 

No one has mentioned the fact that a Lithium Ion battery is made using interleaved flexible separators. These will attract and repel each other as the power is switched on and off by the PWM controller.

Thank you so much Sir.
Other experts answered “Why?” and you answered “How?” and now perfect. I realized all I wonder.
Thank you very much.

 

There are other possible sources for the sound found one the cell’s protection board. SMD capacitors can experience piezoelectric effects that will cause them to produce an audible sound.

I have also heard of, though never personally confirmed, cases of MOSFETs singing along with the PWM.

You can track down the noisy component by gently applying pressure with a non-conductive probe (wood, plastic, bamboo, etc.) to each component. If you touch the right one, you should be able to influence the amplitude of the sound.

For the LiPo, you could just push on it with a finger and see if you can modulate the amplitude that way.

 

Why it is happening. Could you please someone explain me ?

Powerbank contains converter 3.7 V to 5 V.
Ferrite core of converter's inductor "sings"
because of magnetostriction effect.

 

Powerbank contains converter 3.7 V to 5 V.
Ferrite core of converter's inductor "sings"
because of magnetostriction effect.

Inductors are the most common source for the reason mentioned. If you are using the boost converter that came with the power bank this is the most likely explanation. I assumed (possibly erroneously) that you were using just the cell since you said you weren’t "using the power bank” and just not using the housing isn’t not using it.

 

Use a lead acid battery or bench power supply to power the LEDs and see if the buzz goes away.

 

Hello, I’m using an old power bank battery for LED panel with 166 LED. (The seller said it is 80w). This panel has 8 steps of brightness and can control by remote control. The strange thing I‘ve noticed is when I’m using it with decreased brightness, I hear the whining sound like a buzzer from the battery. But with full brightness , whining sound has gone. (You can see in my attachment video link ). I don’t know it’s dangerous or not and Why it is happening. Could you please someone explain me ?
Video link: https://youtube.com/shorts/h2ekFf_2nhM?feature=share

Thank you so much.

View attachment 298061
View attachment 298062

If it is the battery try a 100uf low ESR capacitor across the battery terminals.
After that the battery will get lower level pulse currents.

If you suspect the inductor, try squeezing it to see if the noise increases or decreases. You can also try a very small values resistor in series with the inductor, like 0.02 Ohms or just a length of wire. That reduces efficiency though.