Maha C9000 hi pitched sound

[condor11]

I have C9000 version 0G0D01 and it makes hi pitched (but not loud at all) sound when charging the batteries. Sound is not continuous but is like 2-second sound then 2 second rest. Is this sound normal

My newer C9000 version 0H0FA is quiet.

 

[Mr Happy]

Yes it's normal. It comes from the switched mode DC/DC converter circuitry inside it. It's more surprising that you have one that's quiet.

 

[wapkil]

Yes it's normal. It comes from the switched mode DC/DC converter circuitry inside it. It's more surprising that you have one that's quiet.

My 0H0FA C9000 is also completely quiet. I have other chargers that have this annoying high pitched noise and I read that the C9000 also makes it so I checked before buying. The only sound that I could hear was a silent "click" approximately every 2 seconds. It could only be heard if I put my ear next to the charger. Maybe Maha changed something in the design that practically eliminated the noise (e.g. caused that it has a frequency impossible to hear)...

 

[Black Rose]

My C9000 (0G0KA) makes the high pitched sound, but my C800S clicks.

 

[condor11]

Looks like Maha did change something in the newer models.
BTW, which C9000 revision is absolute latest as of today?