External SSD disconnects at night w/ error notification about not being ejected properly

Get an AC/DC charged USB hub. Energy Saver does not supply enough power for the ports, and causes problems with disconnects. Your system settings can alleviate it a bit by not putting hard drives to sleep, but that's not a permanent solution. Having a hub with its own power source, or drive with its own power source is a much better solution.

Another alternative would be to just shut down at night and reboot in the morning. Being all solid state a reboot shouldn't take more than 30 seconds, not a big inconvenience. An additional benefit of shutting down each night is that it clears out temporary system and application cache and swap files.

For self powered hubs check out OWC (MacSales.com) which is considered by many here to be the premier 3rd party hardware supplier for Macs. Their Customer Support can point you to a hub that will meet your workflow and budget goals.

Yes, I usually use Screen Saver instead of Energy Saver. Too much doesn't support low power energy saver mode.

The performance should actually improve with a powered hub, because then the power dedication of the computer would be less. I know it seems counterintuitive. Just remember the slowest USB that is connected will slow down everything else on the same bus. The System Profile report in Apple menu -> About This Mac shows you how the buses are dedicated to each USB port as you connect more items to USB. Try the Energy Saver setting. If it continues though then I would definitely get a hub. You don't want to be writing data if it is underpowered anyway, as the file being transfered can get corrupted in transit.

Check the firmware of the SSD case. It depends on which kind of chip being used there.

Realtek RTL9210 or Intel JHL7440 or ASM2464, different firmware versions might have different behaviour for power management. Some version might lead to sleep issue causing disconnection.

If using USB-A port, the power output from USB-A port is also a factor to consider.

I ever encountered the issue of disconnection, and resolved by using a USB-C to A(Dual plugs) cable for extra power to SSD case. (2 USB-A ports will be occupied though).

I had the exact same problem. One of my SSD's would keep disconnecting over night when my computer went to sleep. Even though I had set my system settings to do not put drives to sleep. This went on for about 2 months up to the point where it fried my SSD and destroyed it. What I have just done is purchased a powered drive for my main work drive and have that plugged in via the USB A. I then run a 500g NVME SSD-C drive out of the Mac mini M1 and a Sandisk 1TB extreme through a hub out of the 2nd USB A slot. So far after 2 weeks there have been no kick outs of drives. Even when I leave my M1 running overnight, the drives are all attached the next morning. I was running a none powered drive as my main work drive previous to this. Adding the powered drive seems to have fixed the problem. I think the power drain on the M1 was causing the issue.

So, I've been having a similar issue with my USB-C portable drive connected to my Macbook Pro 2023 16". When traveling, I use the external drive for my Photos Library and have my library set to download originals to this Mac. I often import photos from an SD card into the library and leave the machine on with the Photos. App open.

I noticed that the external drive ejects after 15-30 minutes, and I get a warning that the drive was disconnected before dismounting.

After testing leaving the drive connected WITH and WITHOUT the Photos app open, it appears that the drive only ejects when Photos.app is open. When it's not open, it doesn't appear to disconnect. However, soon after the app loads, the drive then disconnects, causing the error.

So logic tells me that something Photos is doing something that causes the USB-C portable drive to eject.

I should note when I'm home, I have a duplicate Photos Library on an external 3.5" drive in a powered enclosure and when connected at my home set that library as System Library so that it will sync with all the photos imported when traveling and imported into the library on the external portable drive.

Does anyone experience similar behavior?

Etrecheck - the handy reporting tool for … - Apple Community

should tell us if some background application is running that is causing problems.

Thanks for the feedback. Good to hear is was solved.