Don't want to start throwing volts, amps, watts, flux capacitors or dilithium crystals around, but here's some empirical data from our experience with the Dometic.
We find we have no problem with the TM battery being fully charged after a full day (10 plus hours) on the road. Our TM battery is a WalMart deep cycle marine battery (just one), and probably about 18 months old. Nothing special. No solar. No dilithium. I should probably modify this statement to say that we had extreme problems with TM battery drainage and fridge performance initially, until we discovered that Ford does NOT install the fuse and relay for the 12vdc charging circuit. You have to do that yourself. Even if you have the factory tow package.
Once we plugged those in, life has been good.
We are not boon-dockers, so we camp where there is electricity. But since we are selling our TM
we've had one potential buyer ask "How long will that fridge run on just the battery?" That got me curious, so I ran a very simple test. I turned the fridge on, and attached a voltmeter to the battery. I measured the voltage drop and fridge temp periodically. The science was primitive; I just wanted to see if I could answer the question the next time it was asked. Over the next 48 hours, the voltage dropped .9 vdc while the fridge temp held (basically) rock steady at 39 degrees. The ending voltage was 12.5 vdc. Remember, this is with a Wally World battery, not dual turbocharged racing 6 volt golf cart batteries. No solar panels. The ambient temps were very mild (highs in the mid-70's) and I did not have any other DC drains in play (other than the typical ghosts), so this wasn't a very vigorous test, but it answered, at least for me, the question "Can I stop for a couple of hours with the TV turned off without worrying about the fridge?"