USB mouse disconnects when i plug in laptop power

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USB mouse disconnects when i plug in laptop power

usb mouse works perfectly when on battery but as soon as i plug in the power it disconnects and stops working completely. unplugging and replugging wroks foir 5 seconds then disconnects again.. mouse has worked fine for years on 2020 macbook air m1 and 2025 macbook air m4, never had a problem. this problem is on a m4 macbook pro brand new.. somewhat disappointed and at this point i miss my m4 air

MacBook Pro 16″, macOS 15.6

Posted on Aug 25, 2025 4:02 PM

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Answer 1

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Tesserax

Level 10

158,490 points

Aug 26, 2025 9:10 AM in response to Pip808

What you’re describing sounds less like a mouse issue and more like a USB power delivery / grounding problem that only shows up when the MacBook Pro is on external power. The fact that it disconnects consistently when the charger is plugged in points to either:

Power/ground noise from the power adapter interfering with the USB bus, or
A potential port-level driver/firmware issue ipecific to the M4 Pro hardware.

Here are a few things you can try to narrow it down:

Try another power adapter and cable. If you’re using a third-party adapter, test with the original Apple one.
On the M4 Pro, different ports may be managed by different internal controllers, and moving the mouse dongle to the opposite side of the Mac can bypass the issue.
Test with a powered USB hub. If the mouse stays stable when the hub provides its own power, that confirms it’s a power negotiation issue on the Mac side.
Reset SMC/low-level power management. On Apple silicon, this is just a full shutdown → wait 30 seconds → restart. Ref: Reset the SMC on your Mac - Apple Support
Create a new macOS user or boot into Safe Mode. This rules out software conflicts or corrupted USB drivers. Ref: Use safe mode on your Mac - Apple Support

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