It just stops before 100% and never completes!! Either that or it copies about 4 gigs and dies Even tried dropbox once.... also failed around 4 gigs. Very frustrating since this is a backup file....
4 GB is the filesize limit for FAT32, which is the standard format for SD cards. Consider uploading it to a cloud service like Google Drive or Dropbox, then downloading it to the phone from there.
If you format your card as exFat instead of Fat32 you should be able to do that. Of course, if you have other data on the card you will need to back it all up before reformatting
You could use a tool like 7Zipper or a similar ZIP tool to make a multipart ZIP file, most archive tools on other platforms (Windows, Mac, Linux) can put it back together with no extra interaction from you.