Pi Drive and other WD USB drives

I have purchased the Pi Drive 1TB kit and have installed it and it works well. I have another 80GB WD Sata drive with an after market power supply and USB adapter. When I am in Ubuntu 16.04.2 Installed in Berryboot I can see and access the 80GB drive. However, when in the backup button from the edit menu I can’t see this drive. The Pi Drive is sda1 and the 80GB drive is sdb1. I would like to use this hard drive for my backups and once done not use it until needed again.