I throw away the swollen battery of my xiaomi earbuds2 but I wanted to use it without the case battery. It doesent charge without battery, so I connected the battery protection board to the board. It worked, but it makes a loud high pitched noise and kinda concerns me. Is it safe? And how do I reduce that noise?

 

It may not be safe because the voltage may be to high. Adding a DC filter is not terribly complex, but the very first thing is to measure the voltage because it may be excessive and cause damage or destruction.

 

It may not be safe because the voltage may be to high. Adding a DC filter is not terribly complex, but the very first thing is to measure the voltage because it may be excessive and cause damage or destruction.

Earbuds are getting 5.2 volts. It looks not that bad I guess. Only the noise concerning me.

 

That battery did provide a good noise filter so now you will need to add some in-line noise filtering to remove that high pitched noise.

 

That battery did provide a good noise filter so now you will need to add some in-line noise filtering to remove that high pitched noise.

Uhm, I obviously don't know how to do it. Can you provide some schematics? I have a solder and bunch of electronics so I think I can buit one. Is it something like that? (Found it online)

 

Uhm, I obviously don't know how to do it. Can you provide some schematics? I have a solder and bunch of electronics so I think I can buit one. Is it something like that? (Found it online)
View attachment 330635

AKA "Pi filter"

 

Like the circuit shown, EXCEPT no damping resistor needed. And probably more like one Millihenry, not MICRO henries.