Can you upload a custom certificate to the Powervault Manager web interface?
Dell Powervault Manager
Dell ME4 storage
You can create your own certificate, but it requires the use of FTP. The following article from Dell shows the steps you need to take to perform the upload.
If you want to view the certificate currently being used, click the down arrow at the top of the Powervault Manager window in the System/Version section and click "Show Certificate Info".