Not necessarily. You haven't said what Uncs rig is and how it is powered electrically. Many converters supply what is known as dirty DC. The older units from the 60s and 70s would let you do this. The various appliances that ran on 12 volts did not have the sophisticated electronic control sy6stems we have today and dirty DC was fine. In this day and time we need the battery if for nothing more than an electrical filter to cleanup that dirty DC because todays systems will not respond to dirty DC. PC boards and computers not only like the proper voltage but insist on it.