Most 12 volt boat refrigerators today have Danfoss compressors with
brushless motors inside and an electronic motor control as a separate
unit or Swing compressors which are pulsed on 12 volts by
electronics. Running these units direct from the battery charger
without a battery as a buffer can be a $300 mistake. To learn more
about refrigerators running off battery chargers go to
http://www.kollmann-marine.com and click on BATTERY STRESS.

Richard Kollmann
Author of books on boat refrigeration.