The first thing I'd do is double check the battery install to make sure they're wired correctly. You didn't say what kind and how many batteries you have and if any of your 12v circuits (lights, etc.) are working.
For example, if you have two 12v batteries, you might have accidentally installed them in series and are getting 24V out. If you have two 6v golf cart batteries, you might have accidentally installed them in parallel and are getting 6v out.
Additionally, you should check the EMS to see if it has an internal fuse or fuses on the circuit board that's blown.
2002 Itasca Suncruiser 35U