Root owns removable drive and rsync won't work

I'm using rsync to back up to a usb key
rsync -r -t -v -a /home/pc/AGS/ /media/DIESEL/pc/AGS/
It worked fine for a long time, and then not so good. Running from the command line there are a lot of complaints about 'can't chgrp ...'. It's formatted to fat32 so I can read it in all kinds of machines if I need to, so I gather that's why chown and chgrp don't work, certainly I can't get them to work from the command line as su. What I want to do is to have the whole USB key owned by my ordinary login not root. I've gone through reformatting it with gparted, but I can't find any way to set permissions on the volume, and it seems to get set up automatically with root ownership. Is there any way to either set up the volume so my ordinary login can do whatever it wants with the volume, or else is there a way to have my little script work ok even though I don't own the volume?