Will TT Kill Truck Battery When Rig is Parked?

[Arch Hoagland]

Unplug the trailer when it's going to be sitting for a spell.

[Justa1Gary]

You should also check the RV converter, if the converter stopped working your normal parasitic battery drain after a week would definitely contribute to a battery drain in your truck when hooked up. I believe most converters kick on anytime the DC voltage drops below 13 DC volts, but you also need to make sure your house hold current going to the trailer is at least 115 volts AC or more. The gauge of your electrical cord can really make a difference in what voltage your getting to the trailer.

I bought a new trailer that had a unknown bad converter and the first 2 nights I stayed in a full hookup site without unhooking the truck and trailer resulted in 2 dead diesel batteries. :(

[hillbilly3]

It is most likely the brake controller, usually the controller has a small current draw when connected to the trailer.

[Pappion]

My 4 Runner only connects power to TT connector when running. It has a built in RELAY, in the fuse box. AKA: solenoid.
A fellow camper had a pickup with a tow package. No Relay and TT killed the battery.
A relay can be added. Those with the knowledge and imagination need no instructions. All others seek pro help.

[hillbilly3]

My brake controller stays lit when a trailer is plugged in. It will kill the battery if left connected for a week.