Unsupported compression type

I am having a problem extracting backup files created using the zip Backup Format. When trying to unzip using 7-zip 9.20, I get an error “unsupported compression type”. This is happening with a 5GB zip file (backing up over 6GB of files). I am also setting a password on the zip file.

Small zip format backups unzip without a problem. I am guessing that there is an upper limit to the size of zip archives? If so, what is that limit?

I have run into a similar problem with the self-extracting cbu files. Is there also a file size limit on these?

I would really like a backup solution that can be restored without installing the backup program. I will try simple file copy next, but I would also like a backup that is password protected.