Backup databases in an Availability Group

CREATE PROCEDURE sp_AGDB_Backup
AS
IF (SELECT   COUNT(*) 
         FROM sys.availability_groups ag
       INNER JOIN sys.availability_databases_cluster adc
             ON (ag.group_id = adc.group_id)
       INNER JOIN sys.dm_hadr_availability_replica_states dhars
             ON (dhars.group_id = ag.group_id)
       WHERE dhars.role = 1) > 0
       BEGIN
             DECLARE @sql NVARCHAR(1000);
             DECLARE @path NVARCHAR(500);
             DECLARE @ext NVARCHAR(10);
             DECLARE @cmd NVARCHAR(1000);
             DECLARE @dbname NVARCHAR(100);
             DECLARE @role int;
 
             SET @sql = 'BACKUP DATABASE @dbname TO DISK = N''';
             SET @path = 'C:\Backup\';
             SET @ext = '.bak''' + ';';
     SET @role = 1; --Sets to backup on Primary
 
             DECLARE a CURSOR
             STATIC
             FOR
             SELECT adc.database_name
               FROM sys.availability_groups ag
             INNER JOIN sys.availability_databases_cluster adc
                    ON (ag.group_id = adc.group_id)
             INNER JOIN sys.dm_hadr_availability_replica_states dhars
                    ON (dhars.group_id = ag.group_id)
             WHERE dhars.role = @role
             ORDER BY adc.database_name ASC;
 
             OPEN a;
 
             FETCH NEXT FROM a
             INTO @dbname;
 
             WHILE @@fetch_status = 0
                    BEGIN
 
                           SET @cmd = REPLACE(@sql, '@dbname', QUOTENAME(@dbname)) 
+ @path + @dbname 
+ '_' 
+ REPLACE(REPLACE(CONVERT(VARCHAR, GETDATE(), 120), ' ', '_'),':','-') 
+ @ext;
 
                           exec sp_executesql @cmd;
                           --PRINT @cmd;
 
 
                           FETCH NEXT FROM a INTO @dbname;  
                    END;
 
             CLOSE a;
             DEALLOCATE a;
 
       END;