This is the shell script I run on a rpi each morning 2 hours after the scheduled backup and it doesn't appear to create a new backup on the HE hub.... Don't ask me to try and remember what each part does 
My guess is it grabs the list of local backups from the web page and finds the most recent one, then downloads it. The bit at the beginning keeps 14 days worth of backup files on the rpi.
heName='HERULES03'
heAddr='192.168.x.x'
backupdir='/data/backups/hubitat/HERULES03'
cd $backupdir
ls -1tr | head -n -14 | xargs -d '\n' rm -f --
curl http://$heAddr/hub/backup | grep download | awk -F"=" '{ print $4}' | awk -F'"' '{print $2}' | sed '/^$/d' | tail -1 | xargs -I @ curl http://$heAddr/hub//backupDB?fileName=@ -o $backupdir/HERULES03_$(date +%Y-%m-%d-%H%M).lzf
There was a thread from a while ago where various alternative scripts were discussed, including some powershell one's I think...
