Today my hds-7 gen 2 gps/sonar flashed while using the trolling motor and the screen got darker. Could this be a bad battery,or a bad or loose connection. When I had a Lowrance X510 c, I could check the voltage using the unit.I am not sure this unit will do this,or I can't seem to find out how. It is connected to the trolling motor battery, should I connect it to the cranking battery. Anyone have any ideas? Thanks for any input.