The key bit here is "How can I run a batch file when the pc is off
When a PC is powered down, the processor is not running, and no applications, scriopts, or batch files can execute on it.
If it's hibernated, or sleeping then it's possible to wake it on a timer: How to Make Your PC Wake From Sleep Automatically
] but then you'd probably need to run your batch file as a service as no user is probably logged in when your batch file ran.
And if it's not connected to a network, then you can't access any other machine via FTP either ...