Laptop charger is buzzing

I think I’m in trouble here. 😁

Got this relatively new HP's laptop, but the warranty expired a few months back. A few days ago, I noticed the charger makes this buzzing sound after I unplug it from both the wall and the laptop. If you put your ear right up to it, you can hear it—it's not deafening, but definitely audible—for about 30 seconds before it dies down.

Did some digging and realized the charger actually buzzes constantly when it's plugged into the outlet but not connected to the laptop. It sounds like a little "bzz" noise. As soon as I plug the barrel connector into the laptop, the buzzing stops and it goes silent. If I pull it out of the wall, the buzzing starts up again, lasts 30 seconds, and then quits.

I'd bet anything this wasn't happening before; it just started doing this weird thing where it buzzes while plugged into the wall alone. Is this dangerous? Why is it doing this? And does it have anything to do with the fact that my battery is basically dead—it barely holds a charge for 5 minutes max, so I'm living on the charger 99% of the time?

Speaking of the battery... everything was totally fine six months ago, holding a decent charge, and then suddenly it just tanked to five minutes without any warning. Not sure if they're linked. I called Zelcos tech support about it, but they told me their policy is only a one-year warranty on batteries, even though the rest of the laptop gets two years, so I just gave up on them...

Thanks for the help. 🙂

Honestly, most power adapters hum a little bit, more or less. It’s probably just a coil that isn't properly "potted," or maybe you'll need to swap out a capacitor down the road, but it's really not the end of the world. The difference in noise when the laptop is plugged in versus unplugged just comes down to how much load the adapter is under at that moment.
In theory, leaving an adapter plugged into the wall shouldn't matter since it pulls next to nothing—like, 0.1W tops. Unless, of course, you're one of those hardcore environmental activists who calculates the standby power of every single adapter in the city just to "freak out" over a few cents a year...
I have a whole pile of phone chargers plugged in all over my house; anyone walking by can just grab whatever they need.

On the flip side, if they're sitting somewhere where they might get bumped, or if the cable or connector gets crushed (maybe by a chair or something), you could run into shorts or overheating issues. You should probably move it to a safer spot... or just unplug it if you're going to be away for a while.
The only way this becomes a real issue is if you're 100% sure it wasn't whining before, but now it's making a noise that's totally unbearable. In that case, you could take it to a local repair shop or some general electronics technician (the kind that fixes TVs and stuff); they can usually pop it open and swap a tiny part for the price of a pizza. There are also some solid, high-quality replacement adapters from reputable brands like Fortron that won't break the bank.

Regarding the battery: what we call a "charger" is actually just a rectifier. The actual intelligence lives inside the battery itself via some control circuitry that manages the charging cycle and monitors the battery's health. It's possible that once it detects a cell has degraded significantly, it triggers a safety lockout to stop further charging. (My own laptop battery completely "locked up" after about a month of sitting unused: it used to last an hour, then suddenly it wouldn't last a second, though the laptop works fine on the adapter).
Since your battery is basically useless now, you can just pop it out and run everything "off the cord." OEM batteries are way too expensive compared to what a used laptop is worth, and I usually steer clear of third-party replacements because they rarely hit even half the performance of the original... but hey, if mobility is your priority, you pay the price.

Personally, I think buying a laptop instead of a desktop is a questionable move if you don't actually need to move around—like, if you're always plugged into a wall... but people, habits, whatever...

thanks for the deep dive! 🙂

honestly, I was mostly freaking out because I’m pretty sure this sound wasn't there before, and now it’s popping up in those exact moments I mentioned. I don't know the first thing about electronics, so I figured it's better to ask than to wait for something to blow up. It’s not like it's deafening or anything—you really only hear it if you press your ear right against it or get super close—so it probably isn't dangerous. Thanks for calming me down though; I'll keep an eye on it. If it gets worse, I'll just take it to a repair shop or toss it in the trash.

I checked with an authorized service center about the battery price, and they sent over a quote for about $233. Felt like a total rip-off, so I'm just dealing with it as is. I am NOT dropping $233 on a battery...

Ethan Harris52 said:thanks for the deep dive! 🙂

honestly, I was mostly freaking out because I’m pretty sure this sound wasn't there before, and now it’s popping up in those exact moments I mentioned. I don't know the first thing about electronics, so I figured it's better to ask than to wait for something to blow up. It’s not like it's deafening or anything—you really only hear it if you press your ear right against it or get super close—so it probably isn't dangerous. Thanks for calming me down though; I'll keep an eye on it. If it gets worse, I'll just take it to a repair shop or toss it in the trash.

I checked with an authorized service center about the battery price, and they sent over a quote for about $233. Felt like a total rip-off, so I'm just dealing with it as is. I am NOT dropping $233 on a battery...

You know, there's actually a specialized battery shop over on George's Avenue in Washington, D.C., where they can fix yours up for you. They did mine recently and it only cost me about $133, and honestly, the battery performs even better than it did when it was new...