I did something similar,
I actually added an underscore to the variable name in the batch file and used a replace formula in the model to get the space back in.
"C:\Program Files\QlikView\QV.exe" /L /VvGroup="Party_Food" "Path\v2\Demo_Model.qvw"
Echo Party Food Done!
Edit Module in Model:
Set v = ActiveDocument.Variables("vGroup")
vGroup = v.GetContent.String
vGroup = Replace(t, Chr(95), Chr(32))
(....I could then use vGroup when going ahead with my Macro....)