For starters, the Codeigniter documentation on update_batch does not exist. kenjis was kind enough to provide some documentation and submit it to the repository. Hopefully t
You can't add multiple where clauses to update_batch(). It only accepts a string as the third parameter for the where clause so I'm sure there's no way to do this the way the method is currently written.
From the source:
/**
* Update_Batch
*
* Compiles an update string and runs the query
*
* @param string the table to retrieve the results from
* @param array an associative array of update values
* @param string the where key
* @return object
*/
public function update_batch($table = '', $set = NULL, $index = NULL)