Is it safe to disconnect external Time Machine backup drive, if the encrypting is not finished? I have set up a 4TB external USB drive to use as a backup for my 2TB MacBook Pro. Everything seems to work all right, but the encryption takes forever, and the Time Machine insists on it being performed only when the computer is plugged in into a power outlet.

Since I would like to use my laptop as intended (as a portable computer), what can possibly go wrong, if I disconnect the backup drive, while it is still encrypting its contents?

I am running the latest Sierra on the 2016 MacBook Pro.
After encrypting the drive for a few days (while the drive was disconnected a few times, and then connected again), Time Machine has finally finished with it and now only runs backups. Nothing indicates a problem, so I think it was all right--the encryption would pick up at the same percentage it was when disconnected, and continue, until done.