Agree. My fridge draws 17 amps DC x volts incoming = watts. However, output on the charge leads can drop to under 2 amps when truck battery is charged and alternator cuts back (as measured with my clamp meter).
Again still not a big deal if running for a day and have two batteries, but a much better setup is to do what jbell has noted. Running on propane eliminates this issue with propane supplying the greatest amount of heat of the three cooling modes.
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC