Here is how to create a Scheduled Refresh to an IBM Database  in PowerPivot:

Create 2 SSS IDs:

PowerPivotDataRefresh

a. Create a SSS application using Group leaving application Page URL to none.

b. Utilize the Windows Username/Password template.

c. Setup members that need to access this SSS application ID.

d. Then set credentials with domain windows credentials.

a. Create a SSS application using Group leaving application Page URL to none.

b. Utilize Username/Password (“IBM Username” “IBM Password”) template.

c. Setup members that need to access this SSS application ID.

d. Then set credentials with IBM credentials.

On the PowerPivot "Configure Service Application Settings" page, set the "PowerPivot Unattended Data Refresh Account" to PowerPivotDataRefresh.

Browse to the PowerPivot Gallery > Locate the workbook you want to Schedule a Data Refresh for > Click “Manage Data Refresh”:

Under “Data Refresh” tick “Enable”

Under “Schedule Details” tick “Also refresh as soon as possible”

Under Credentials > Select "Use the data refresh account configured by the administrator"

Unselect "All Data Sources"

(In this case) Select "Custom"

Under "Data Source Schedule:" > Select "Use Default Schedule"

Under "Data Source Credentials:" > Select "Connect using the credentials saved in the Secure Store Service (SSS) to log on to the data source.  Enter the ID used to look up the credentials in the SSS ID box.”

ID: PPIVSSS

Click “OK”

Browse to the PowerPivot Gallery > Locate the workbook you want to Schedule a Data Refresh for > Click “Manage Data Refresh”: to view the results.

The error was thrown:

The .Net Framework Data Provider for OLEDB (System.Data.OleDb) does not support the Microsoft OLE DB Provider for ODBC Drivers (MSDASQL). Use the .Net Framework Data Provider for ODBC (System.Data.Odbc).

I opened the workbook in Excel > PowerPivot > Design > Existing Connections > (In this case) “Custom”:

The Connection String: showed the user was using the (Microsoft OLE DB Provider for ODBC Drivers):

The connection string was:

Provider=MSDASQL;Persist Security Info=True;User ID=n94alana;Initial Catalog=S0675035;DSN=Barney

I had the user choose the IBM driver (IBM DB2 for i5 OS IBMDASQL OLE DB Provider):

The connection string is:

Provider=IBMDASQL;Persist Security Info=True;User ID=n90joanne;Data Source=BARNEY

They made the above changes to the workbook connection(s), uploaded the workbooks, and followed the above steps to properly (re)configure Data Refresh(es).