SQLPLUS variable definition within executed file

A moderately frustrating thing, found recently when trying to set up a batch file that causes a SQLPLUS script to run. Specifically, most of the material works just fine, but an important catch has to do with the SQLPLUS DEF/DEFINE preprocessor-esque functionality. The batch file does what it's supposed to and starts the script. The script's logic is sound. However, the script also prompts for the user to provide the &-marked values at runtime, which is specifically NOT what is desired. Text of files is as below. (login is done via external identification)

batch_runner.bat:

sqlplus /@service_id @batch_runner.sql