Works fine here. Ensure you have a Battery 2 mapped track selected, expand the Param header and select Device. There should be a VST Parameters node in the tree containing all the automatable VST parameters. The first one is already set to Inst Volume, the rest are free to map as you want.
Right click on a control in the Battery 2 GUI to list all the automation mappings. Choose an unmapped id and press Set to link the parameter to this control.
The parameter can now be automated using the matching VST in the Podium browser. ID 1, for example, corresponds to VST Parameter #001. These can be renamed in the properties dialog for each node, which is recommended if you’re using a lot of automation mappings.