Some of the older converters had very poor filtration and regulation and used the battery as a filter. I replaced the Parallax converter from my 2001 Safari with a PD9260. I am, and have been, using the Parallax as a 12 VDC supply for radio testing with no adverse results. It's a not so great battery maintainer, but a good power supply.
“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins