HP Envy x360 Extremely Loud Squealing when Fully Charged

[JDavies7]

Hi all,

I bought an Envy x360 15-cn0007na (product # 4TX40EA) in January 2019, and it has always made an extremely loud squealing sound when plugged in and fully charged. I have always made a point of unplugging it when fully charged as I don't know what the BMS' capabilities are when it comes to overcharge protection, but the instant the battery charge hits 100% the noise starts and it seems to be worsening with time (either that or it's bothering me more and more with time!).

To describe the noise more, it's a kind of screechy-squealy-squeaky sound that seems akin to what I'd imagine a laptop being electrocuted would sound like - not like coil whine but something far more serious. I've read lots of threads about similar issues but none seem quite right, although with a problem this nondescript it's likely that other people have had exactly the same issue and I have misinterpreted their description of it.

It's worth noting the laptop has never been dropped or damaged, and the battery charges and discharges perfectly. It doesn't seem to be a fan catching, as the flow from the side vent seems fairly powerful under load, even if the laptop does run a bit hot when taxed (I do a lot of serious CAD work and rendering). When charging up to 100% (all the way up to 99%, at least) there's no sign of the noise, and no noise when running on battery power either, other than a faint whine coming from the screen but I didn't think that was an issue (?). Just for clarity, the screen whine is there whether on battery power or plugged into the mains, but normally when the laptop is plugged in I'm at my workstation with it hooked up to a couple of monitors (and the laptop screen switched off), so of course, the screen whine would be gone.

I'm really at a loss here. I'll gladly admit to being out of my depth when it comes to servicing modern notebook-style laptops, and I can't provide a better description of the screechy-squealy-squeaky sound because it's as alien and nondescript as it gets. I remember thinking a while ago it only occurred when fully charged AND when the MX150 dedicated graphics pseudo-card is fired up, but now it seems to be there whenever the battery percentage reaches 100.

I'd be very grateful for any help or advice as to what on earth this noise is and how I can get rid of it. Or maybe it's nothing more than an annoyance and doesn't pose any risk to the laptop?

Thanks in advance.

Note: I know how annoying or frustrating it can be when someone comes to you with a problem and can only describe it as a vague sound that could be any one of a thousand issues, so please bear with me! I work with cars a lot, and it can be maddening when a friend drops off their car saying "Oh, it's making this awful clunking noise" and all I can think is 'Fantastic, you've narrowed it down to quite literally every moving part, and even some fixed ones too, from a goosed damper to a knackered bushing to even a branch jammed around the driveshaft!' (it happens).