6V lantern battery

My guess was this trailer was towed by a vehicle with a 6 volt system and if so this was most likely the battery for the break away switch.

mel , your Compact does not have a dome light installed in the ceiling anywhere with a switch directly on the side does it?



I know they used these in the Airflytes and the 16SC models in the early 60's, the one above is in my Airflyte.  It had a pair of leads in the top of the cupboard to the right, and used one of those 6-V lantern batteries to power it.  It made it a stand-alone light independent of any of the other wiring/lighting systems. 






Those batteries were used a lot in the 60's for all different types of lanterns.  Some had the screw posts like yours, and later they were made with spring-top contacts which would basically press-fit inside the lantern casing.




Since your trail leads you back to the trailer wiring harness, I would think bigbill's idea probably the most likely.  Even if the vehicle were not 6-v, the lantern battery at full should be enough current to activate brakes in an emergency situation.

Law required a trailer mounted battery to operate brakes in case of a break away enough to stop trailer so many of them used lantern batteries to stay legal. They were cheap and plentiful. Some trailers had a tongue mounted case to carry them in.

Break -away switches still have to be powered from the trailer. Some of the modern kits include a battery-pack that recharges from the vehicle when hooked to tow wiring. It can also be run from the battery which powers the 12-V system in the trailer itself. 


In the event of a break-away, the trailer would no longer be connected to the vehicle battery power, thus requiring a power source contained in the trailer's system, to apply the electric brakes.