The home and car volumes are saved separately. When you move it between home and car, it will properly remember your desired volume for each location.
If it doesn't, then there's a problem with the power connector, see the troubleshooting section of the FAQ at
www.riocar.org for details.
If you choose to upgrade to the beta version 2.0 (do so at your own risk, it's not 100 percent stable yet), there are a couple of features to help you. First is the "0db cap" available as a setting in Emplode. This prevents someone from turning the player up above 0db and into overdrive. The second is the ability to lock the volume at a given setting, in the player's main menu. Again, this is saved independently between car and home settings.