Paul_Heuvelhorst

Just a couple of additional comments to what others have offered.

If you are towing with a Ford product, factory equipped with the "tow package" your vehicle already has the vehicle battery isolated from the trailer battery. That makes unplugging unnecessary. If you are towing with another make vehicle, that doesn't have an isolator, buy one and install it (simple 3-wire connection). Here is an example of what to buy (http://www.campingworld.com/browse/p...1869&src=SRQB). You can buy such products at Kragen, Pep Boys, NAPA, etc.

Secondly, the fridge, when operating on 12DVC draws about 10 amps. That means 10 amps-per-hour. So, if your TM battery (deep cycle RV/marine type) is fully charged, it will take several hours (8 or more) to deplete the battery. If you don't have an isolator on your tow vehicle, then your trailer battery and vehicle battery are connected in parallel, and while the discharge rate is still the same (10 amps), you have twice the battery capacity, so the impact to both batteries is 1/2 of what it is on a single battery.

I am a strong advocate of the isolator solution. I prefer the diode type rather than a relay, but that is personal preference. Either type will do the job correctly.

I have been towing with Ford vehicles for 15 years, so it is a feature built-in to my vehicles. However, one of our sons bought a tent trailer last year and tows it with their Mercury Villager. I personally installed the 7-wire Bargman connector, a battery isolator, and the 10 gauge wire from the isolator to the Bargman connector so their trailer battery would charge while the vehicle was running without any impact on the car battery. It took me about 2.5 hours to complete the project... and I'm over 65, with some background in electronics! ;-)