Did you also try to set the values of the HOME, HOMEDRIVE and HOMEPATH env vars inside the redmineini.bat script?
In order to set them add the following:
And in order to verify the value:
Then execute the .bat script from a terminal.
I would try the above to make sure that the env vars are correctly set.
And just in case you missed this post I am referencing here: https://community.bitnami.com/t/error-during-install-relating-to-homepath-homedrive-variables/34603/17