Problem (Case):
I need backup site granular on my server with schedule time without remove my last backup (create new backup file).
For example:
SiteBackup07022018.bak
SiteBackup08022018.bak
SiteBackup09022018.bak

Solution:

1. Power-shell script functionality for Get GUID & URL Site:
*for this function just execute in sharepoint management shell (run as admin)

Get-SPSite | format-list -property id,url

2. Power-shell script functionality for Backup Site:
*for this function save as .ps1 and put in Task Scheduler

Add-PSSnapin "Microsoft.SharePoint.PowerShell"
Set-ExecutionPolicy -ExecutionPolicy "Unrestricted" -Force
$path="C:\Site" + (Get-Date).tostring("ddMMyyyy") + ".bak"
Backup-SPSite -Identity  -Path $path –NoSiteLock

If any question, leave comment :)